Transparent conductive electrodes are one of the essential components for organic optoelectronic devices, including photovoltaic cells and light-emitting diodes. Indium-tin oxide (ITO) is the most common transparent electrode in these devices due to its excellent optical and electrical properties. However, the manufacturing of ITO film requires precious raw materials and expensive processes, which limits their compatibility with mass production of large-area, low-cost devices. The optical/electrical properties of ITO are strongly dependent on the deposition processes and treatment conditions, whereas its brittleness and the potential damage to underlying films during deposition also present challenges for its use in flexible devices. Recently, several other transparent conductive materials, which have various degrees of success relative to commercial applications have been developed to address these issues. Starting from the basic properties of ITO and the effect of various ITO surface modification methods, here we review four different groups of materials, doped metal oxides, thin metals, conducting polymers, and nanomaterials (including carbon nanotubes, graphene, and metal nanowires), that have been reported as transparent electrodes in organic optoelectronic materials. Particular emphasis is given to their optical/electrical and other material properties, deposition techniques, and applications in organic optoelectronic devices.

Recent progress in the development of materials and devices for single-doped white devices is presented with a particular focus on the development of platinum complexes exhibiting excimer emission. White organic light emitting diodes (WOLEDs) are strong candidates for the next generation of solid-state lighting, yet many of the best devices generate white light using multiple emitters embedded in a comparably complex device structure, raising the difficulty of consistently manufacturing these devices at a low cost and leading to challenges in color stability. These problems can be overcome by fabricating excimer-based WOLEDs, which construct a broad spectrum from a single emitter using blue monomer emission and red excimer emission. Through rational emitter design, the color quality and device efficiencies have steadily improved with recent achievements of external quantum efficiencies over 20% and a color rendering index greater than 80. Furthermore, recent applications of tetradentate platinum complexes for single-doped WOLEDs have yielded devices with a performance superior to many state-of-the-art multilayer WOLEDs as well as promising device operational stability.

This paper reviews recent work on the fabrication of energy storage and power generation using laser-based processes such as pulsed laser deposition (PLD), laser-induced forward transfer (LIFT), and laser surface processing techniques. PLD is a versatile technique for depositing high-quality layers of materials for cathodes, anodes, and solid electrolytes for thin-film microbatteries. Using sequential PLD processes, solid-state thin-film lithium-ion microbatteries can be successfully fabricated. LIFT is a powerful tool for printing complex materials with highly porous structures for the fabrication of micropower sources such as thick-film batteries and metal oxide-based solar cells. In particular, using the LIFT process it is possible to print thick layers (∼100  μm) while maintaining pattern integrity and low-internal resistance. As a consequence, power sources fabricated in this manner exhibit higher energy densities per unit area than those obtained by traditional thin-film growth techniques. In addition, the printed active materials can be modified by postlaser processes, such as laser sintering and laser structuring, to further improve the device performance by enhancing the electrodes’ three-dimensional networked structure and increasing the overall active surface, respectively. This review will discuss various examples where laser materials’ processing has led to new approaches in the development of micropower sources applications.

Organic light-emitting diodes (OLEDs) show potential as the next-generation solid-state lighting technology. A major barrier to widespread adoption at this point is the efficiency droop that occurs for OLEDs at practical brightness (∼5000  cd/m²) levels necessary for general lighting. We highlight recent progress in highly efficient OLEDs at high brightness, where improvements are made by managing excitons in these devices through rational device design. General design principles for both white and monochrome OLEDs are discussed based on recent device architectures that have been successfully implemented. We expect that an improved understanding of exciton dynamics in OLEDs in combination with innovative device design will drive future development.

We review the key optoelectronic properties of lateral organic bulk heterojunction (BHJ) device structures with asymmetric contacts. These structures are used to develop a detailed model of charge transport and recombination properties within materials used for organic photovoltaics. They permit a variety of direct measurement techniques, such as nonlinear optical microscopy and in situ potentiometry, as well as photoconductive gain and carrier drift length studies from photocurrent measurements. We present a theoretical framework that describes the charge transport physics within these devices. The experimental results presented are in agreement with this framework and can be used to measure carrier concentrations, recombination coefficients, and carrier mobilities within BHJ materials. Lateral device structures offer a useful complement to measurements on vertical photovoltaic structures and provide a more complete and detailed picture of organic BHJ materials.

The field of concentrated photovoltaics (CPV) has met some remarkable advances in recent years. The continuous increase in conversion efficiency of multijunction solar cells and new advancements in optics have led to new demands and opportunities for optical design in CPV. This paper is a mini-review on current requirements for CPV optical design, and it presents some of the main trends in recent years on CPV systems architecture.

Cadmium telluride (CdTe) is the most commercially successful thin-film photovoltaic technology. Development of CdTe as a solar cell material dates back to the early 1980s when ∼10% efficient devices were demonstrated. Implementation of better quality glass, more transparent conductive oxides, introduction of a high-resistivity transparent film under the CdS junction-partner, higher deposition temperatures, and improved Cl-treatment, doping, and contacting approaches yielded <16% efficient cells in the early 2000s. Around the same time period, use of a photoresist plug monolithic integration process facilitated the demonstration of the first 11% efficient module. The most dramatic advancements in CdTe device efficiencies were made during the 2013 to 2014 time frame when small-area cell conversion efficiency was raised to 20% range and a champion module efficiency of 17% was reported. CdTe technology is attractive in terms of its limited life-cycle greenhouse gas and heavy metal emissions, small carbon footprint, and short energy payback times. Limited Te availability is a challenge for the growth of this technology unless Te utilization rates are greatly enhanced along with device efficiencies.

When state-of-the-art bulk heterojunction organic solar cells with ideal morphology are exposed to prolonged storage or operation at elevated temperatures, a thermally induced disruption of the active layer blend can occur, in the form of a separation of donor and acceptor domains, leading to diminished photovoltaic performance. Toward the long-term use of organic solar cells in real-life conditions, an important challenge is, therefore, the development of devices with a thermally stable active layer morphology. Several routes are being explored, ranging from the use of high glass transition temperature, cross-linkable and/or side-chain functionalized donor and acceptor materials, to light-induced dimerization of the fullerene acceptor. A better fundamental understanding of the nature and underlying mechanisms of the phase separation and stabilization effects has been obtained through a variety of analytical, thermal analysis, and electro-optical techniques. Accelerated aging systems have been used to study the degradation kinetics of bulk heterojunction solar cells in situ at various temperatures to obtain aging models predicting solar cell lifetime. The following contribution gives an overview of the current insights regarding the intrinsic thermally induced aging effects and the proposed solutions, illustrated by examples of our own research groups.

Polymeric bulk heterojunction (BHJ) organic solar cells represent one of the most promising technologies for renewable energy with a low fabrication cost. Control over BHJ morphology is one of the key factors in obtaining high-efficiency devices. This review focuses on formulation strategies for optimizing the BHJ morphology. We address how solvent choice and the introduction of processing additives affect the morphology. We also review a number of recent studies concerning prediction methods that utilize the Hansen solubility parameters to develop efficient solvent systems.

Recent advances in fullerene-based Schottky organic solar cells (OSCs) are presented, with a focus on the current understanding of device physics. Fullerene-based Schottky OSCs attain high open-circuit voltages due to the n-type Schottky junction formed between fullerene and an adjacent high work function anode. Small concentrations of donor material doped into the fullerene matrix serve as efficient exciton dissociation and hole transport agents that can substantially bolster short-circuit currents and fill factors. As a consequence, fullerene-based Schottky OSCs have been demonstrated to provide some of the highest-performance vacuum-deposited small molecule OSCs, with power conversion efficiencies up to 8.1%. Fullerene-based Schottky OSCs constructed using different donor materials and varying cathode buffer layers, as studied by a number of different research groups, are presented. To elucidate the differences between Schottky OSCs and more traditional bulk-heterojunction OSCs, we discuss the photophysics of fullerenes, the role of the donor material, and charge transport in low donor concentration active layers. Fullerene-based Schottky OSCs possess considerable advantages because they can reach high efficiencies with a simple structure using readily available and cost-effective materials. The impact and applicability of the Schottky device architecture on the field of organic photovoltaics at large are discussed.

We investigated a laser welding process for contacting aluminum-metallized crystalline silicon solar cells to a 10-μm-thick aluminum layer on a glass substrate. We analyzed the threshold for laser-induced damage in dependence on the solar cell metallization thickness by applying the process on SiNx passivated lifetime samples. In addition, we measured themechanical failure stress of the laser welds by perpendicular tear-off. We applied two types of laser processes; one used single or multiple 20-ns-laser pulses at 355 nm with fluences between 12 and 40 J∕cm2, and the other used single 1.2-μs-laser pulses at 1064 nm with 33 to 73 J∕cm2. The ns-laser pulses were able to contact down to 1-μm-thick aluminum layerson silicon without inducing laser damage to the silicon and led to a sufficiently strong mechanical contact. In the case of μs-laser pulses, the limiting thickness was 2 μm. Both laser systems were compared and discussed with respect to the theory of laser-induced forward transfer. Theapplication was shown by contacting solar cells with 2-μm Al metallization on the rear side using μs-laser pulses proving a damage-free contacting.

The effects of tungsten doping and hydrogen annealing on the photoelectrochemical (PEC) performance of bismuth vanadate (BiVO ₄ ) photoanodes for solar water splitting were studied. Thin films of BiVO _4[/sub] were deposited on indium tin oxide-coated glass slides by ultrasonic spray pyrolysis of an aqueous solution containing bismuth nitrate and vanadium oxysulfate. Tungsten doping was achieved by adding either silicotungstic acid (STA) or ammonium metatungstate (AMT) to the precursor. The 1.7- to 2.2-μm-thick films exhibited a highly porous microstructure. Undoped films that were reduced at 375°C in 3% H ₂ exhibited the largest photocurrent densities under 0.1  W cm ⁻² AM1.5 illumination, where photocurrent densities of up to 1.3  mA cm ⁻² at 0.5 V with respect to Ag/AgCl were achieved. Films doped with 1% or 5% (atomic percent) tungsten from either STA or AMT exhibited reduced PEC performance and greater sample-to-sample performance variations. Powder x-ray diffraction data indicated that the films continue to crystallize in the monoclinic polymorph at low doping levels but crystallize in the tetragonal scheelite structure at higher doping. It is surmised that the phase and morphology differences promoted by the addition of W during the deposition process reduced the PEC performance as measured by photovoltammetry.

The wide bandgap, one-dimensional zinc oxide (ZnO) nanowires (NWs) and their heterostructures with other materials provide excellent pathways for efficient photovoltaic (PV) and light-emitting devices. ZnO NWs sensitized with quantum dots (QDs) provide high-surface area and tunable bandgap absorbers with a directional path for carriers in advanced PV devices, while ZnO heterojunctions with other p-type wide bandgap materials lead to light-emitting diodes (LEDs) with better emission and waveguiding properties compared with the homojunction counterparts. Synthesis of the structures with the desired morphology is a key to device applications. In this work, ZnO NW arrays were synthesized using hydrothermal method on ZnO and GaN thin films. Highly crystalline, upright, and ordered arrays of ZnO NWs in the 50 to 250-nm diameter range and 1 μm in length were obtained. The morphology and optical properties of the NWs were studied. Energy dispersive x-ray spectroscopy (EDX) analysis revealed nonstoichiometric oxygen content in the grown ZnO NWs. Photoluminescence (PL) studies depicted the presence of oxygen vacancy and interstitial zinc defects in the grown ZnO NWs, underlining the potential for LEDs. Further, hydrophobically ligated CdSe/ZnS QDs were successfully incorporated to the NW arrays. PL analysis indicated the injection of electrons from photoexcited QDs to the NWs, showing the potential for quantum dot-sensitized solar cells.

Optimal efficiency calculations for 3C-SiC- and 6H-SiC-based intermediate band (IB) solar cells are presented. Using detailed balance methods, it is shown that the conversion efficiency of IB SiC-based solar cells is very sensitive to IB position, type of spectrum, and concentration of the incident light. Under a 1000 suns concentration and AM1.5 spectrum irradiation, a maximum efficiency of 55.9% is theoretically achieved for 3C-SiC with the IB located at 0.79 eV up to the valence band of the host material. Under the same conditions, a theoretical maximum efficiency of 49.7% is achieved with an IB located at 0.84 eV below the conduction band of the 6H-SiC. Based on the obtained theoretical results, the formation of an isolated IB in the appropriate position is demonstrated for Ni-doped 3C-SiC and Mn-doped 6H-SiC using the density function theory method which leads to an enhancement in the absorption coefficient in the ranges of the solar spectrum.

An optoelectronic device simulation framework valid for arbitrary spatial variation of electronic potentials and optical modes, and for transport regimes ranging from ballistic to diffusive, is used to study the nonlocal photon absorption, photocurrent generation and carrier extraction in ultra-thin film, and nanostructure-based solar cell devices at the radiative limit. Among the effects that are revealed by the microscopic approach and which are inaccessible to macroscopic models is the impact of structure, doping- or bias-induced nanoscale potential variations on the local photogeneration rate and the photocarrier transport regime.

This study employs anthocyanin extracts from mulberry (Morus atba Lam) fruit and Akenchira (Striga hermonthica) flower as the natural dyes for a dye-sensitized solar cell (DSSC). The electrodes, electrolyte (I − /I ₃ − ), and dyes were assembled into a cell and illuminated by a light with an intensity 100  mW/cm² to measure the photoelectrochemical parameters of the prepared DSSCs. According to the experimental results, the maximum conversion efficiency of the DSSCs prepared from anthocyanin dyes of Morus atba Lam fruit extract is 0.42%, with an open-circuit voltage (V _oc ) of 0.54 V, a short circuit current density (J _sc ) of 1.38  mA/cm ² , and a fill factor (FF) of 0.56. The maximum conversion efficiency of the DSSCs prepared by anthocyanin dye from the flower of S. hermonthica extract is 0.304% with a V _oc of 0.52 V, J _sc[/sub] of 1.01  mA/cm2 , and an FF of 0.58.

This study reports on an organic solar cell structure utilizing K12 as a new low-temperature processable small-molecule acceptor material. Pentacene (PEN) and K12 were deposited onto indium tin oxide by means of organic vapor phase deposition (OVPD) as bilayer solar cells. The resulting solar cell was characterized electrically by current density-voltage (J−V) measurements and optically by photocurrent and reflectivity measurements. The J−V characteristic under AM 1.5 illumination indicates a short-circuit current of 0.45  mA/cm² (J_sc), a fill factor of 38% (FF), and an open-circuit (V_oc) voltage of 0.71 V. Current generation is found to predominantly occur in the K12 layer, although strong light absorption in the PEN layer is detected. We suggest that either a dipole shift between the layers or the fission of singlet excitons in the PEN layer leads to this observation. Although the efficiency of the device is low in combination with PEN, our experiment successfully demonstrates the use of K12 as a low-temperature acceptor material in OVPD processes.

Zinc sulfide (ZnS) quantum dots were prepared by successive ion layer adsorption and reaction (SILAR) technique based on spin coating (spin-SILAR). The effect of the number of SILAR cycle (n) on optical and photovoltaic properties was studied. An optimized ZnS quantum dot sensitized solar cell demonstrated maximum power conversion efficiency of 3.58% with a short-circuit current of 10.53  mA/cm² and an open-circuit voltage of 0.58 V under one sun illumination (AM1.5). The results showed that a ZnS QD layer with n=10 (thickness ∼80  nm) can be used as a highly efficient sensitizer for solar cells. The ZnS QD layer acts as a light absorber and a recombination blocking layer in the ITO/ZnO film/ZnS QD/P3HT/PCBM/Ag structure.

Low temperature curing of Ag paste for electrode formation in silicon hetero junction (SHJ) solar cells is important for providing better device characteristics. Ag paste is composed of solvent, various organic materials, and additives; hence its electrical and mechanical adhesion properties depend on the curing conditions. The adhesion of the Ag paste was determined by scratch test, whereas the specific contact resistance was measured using the transfer length method. Various Ag electrodes were formed at various curing temperatures within the temperature range of 160°C–240°C, at 20°C intervals. The curing time was also varied for another set of Ag electrodes. With 200°C temperature and for 20-min curing, the critical load of 20.06 N and specific contact resistance of 19.61  mΩ⋅cm 2 were observed. Using the same conditions, the efficiency of the SHJ solar cell was found to be improved by 3.8%.

We investigate the optical performance of dichroic filters used in solar spectrum-splitting applications. Photovoltaic (PV) systems utilizing spectrum splitting have higher theoretical conversion efficiency than single-bandgap PV modules. Dichroic filters have been used in several spectrum-splitting optical system designs with success. However, dichroic filters only achieve ideal performance under collimated incident light. With an incident angle constraint the optical concentration ratio is limited. A high-concentration ratio helps to achieve high-conversion efficiency and control cost by reducing the PV cell area. In a dual-junction spectrum-splitting PV configuration with a gallium arsenide (GaAs) PV cell and a 2.1-eV bandgap PV cell, the experimental dichroic filter can provide 86.3% of the ideal designed performance. The filter nonideal performance under focused incident light is simulated with ZEMAX. System efficiency under different F -number and filter refractive index is simulated for dual-junction and three-junction systems to show the performance of dichroic filters. We have found that for a dual-bandgap spectrum-splitting system there is a 0.32% system efficiency gain associated with a filter refractive index increased from 1.5 to 1.95. An efficiency gain of 0.41% is associated with an aperture size reduction from F2.0 to F3.0 . In a three-junction configuration, simulation shows that a 0.57% system efficiency gain is possible when the filter refractive index is increased from 1.5 to 1.95. An efficiency gain of 0.63% is associated with an aperture size reduction from F2.0 to F3.0 .

We investigate the properties of InGaN-based vertical-type solar cells having wavelengths ranging from the ultraviolet to green regions. It is well known that InGaN-based solar cells require a high indium composition to obtain high conversion efficiency. However, although InGaN-based solar cells with a high indium composition have been fabricated, their conversion efficiency has not sufficiently increased. Therefore, to further understand carrier transport, we measured the bias-dependent external quantum efficiency. For vertical-type green solar cells with a high indium composition, we confirmed that they have a higher short circuit current than other samples tested due to their broader overlapping region with the solar spectrum, though their fill factor remained low due to their high barrier height and strong piezoelectric field, which caused a reduction in the carrier tunneling rate.

We prepared high conducting poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) by solvent additives for using as a hole transport layer (HTL) in polymer solar cells (PSCs). PEDOT:PSS films treated with fluoro compounds of hexafluoroacetone (HFA) and hexafluoroisoproponal (HFIPA) with various concentrations show a significant enhancement in electrical conductivity without compromising optical transparency. The conductivity increased from 0.2 to 1053 and 746  S/cm after 4 vol. % HFA and 6 vol. % HFIPA treatments, respectively. The high performance of the PEDOT:PSS layer is attributed to preferential phase segregation of PEDOT:PSS with HFA and HFIPA solvent mixture treatment methods. The improved performance of PSC was dependent on the structure of organic solvents and the concentration of fluoro compounds in PEDOT:PSS solution. Using these optimized layers, conjugated PSCs with a poly

9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5 thiophenediyl] polymer:[6,6]-phenyl-C71-butyric acid methyl esters (PCDTBT:PC ₇₁ BM ) bulk heterojunction have been produced. The high power conversion efficiency (PCE) of 4.10% and 3.98% were observed for PEDOT:PSS films treated with 4 vol. % HFA and 6 vol. % HFIPA treatments, respectively. The obtained results show that PEDOT:PSS optimized with HFA and HFIPA organic solvents can be a very promising candidate for transparent anode buffer layer in the low cost organic solar cell devices.

Quantum efficiencies (QEs) of innovative hybrid solar cells fabricated using micro/mesoporous zinc (hydr)oxide and its graphite-based composites sensitized by semiconductor quantum dots (SQDs) are reported. High absorption coefficient of CdSe SQDs and the wide band gap of zinc (hydr)oxide and its composites with graphite oxide (GO) are essential to achieve solar cells of higher QEs. Hybrid solar cells are fabricated from zinc (hydr)oxide and its composites (with 2 and 5 wt.% of graphite oxides, termed as, ZnGO-2 and ZnGO-5, respectively) while using potassium iodide or perovskite as an electrolyte. A two-photon fluorescence (TPF) imaging technique was used to determine the internal structure of the solar cell device. The photocurrent and current-voltage measurements were used to measure short-circuit current and open-circuit voltage to calculate the fill factor and QE of these solar cells. The highest QE (up to ∼10.62% ) is realized for a ZnGO-2-based solar cell using potassium iodide as its electrolyte and the CdSe quantum dot as its sensitizer.

In this study, two conjugated polyelectrolytes, polythiophene derivative (PTP) and poly[(9,9-bis [6 ′ -N , N , N -trimethylammonium] hexyl)-fluorenylene-phenylene] dibromide (PFP), are utilized to modify the surface properties of ZnO electron extraction layer (EEL) in the inverted polymer solar cells (PSCs). Both higher short-circuit current densities and larger open-circuit voltages were observed from the inverted PSCs with ZnO/PFP or ZnO/PTP as compared with those only with ZnO EEL. The protonation process for PTP and PFP in solution is distinguished. Overall, more than 40% enhanced power conversion efficiency (PCE) from the inverted PSCs with ZnO/PFP, in which the PFP could be fully ionized in deionized water, and more than 30% enhanced PCE from the inverted PSCs with ZnO/PTP, as the case that the PTP could not be fully ionized in deionized water, as compared with the inverted PSCs with ZnO EEL were observed, respectively. These results demonstrate that the conjugated polyelectrolytes play an important role in enhancement of device performance of inverted PSCs and that the protonation process of the conjugated polyelectrolytes is critical to the modification for EEL in PSCs.

The electronic transport properties of 1, 3, 5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBI) electron transporting layers (ETLs) have been investigated as a function of cesium carbonate (Cs₂CO₃) doping for organic light-emitting diodes (OLEDs). The current density-voltage and light emission characteristics were measured as a function of the Cs₂CO₃-doped ETL thickness. Cs₂CO₃-doped TPBI decreased OLED operating voltage by 26% and increased device luminance by 17% in a wide concentration range (3.5% to 10.5%) compared to undoped devices. The effects of 7% Cs₂CO₃-doped ETL thickness indicated that the operating voltage continuously decreased to 37% when the ETL thickness increased to 600 Å and luminance output continued to increase to 21% at ETL thickness 525 Å. The blue OLED can be optimized by adjusting the thicknesses of Cs₂CO₃-doped TPBI ETL to balance the electron and hole injection.

The down conversion of blue to white light with yttrium aluminum garnet (YAG) phosphor is analyzed theoretically for GaN/InGaN light emitting diodes. A cerium-doped YAG phosphor with particle size of ∼10  μm having peak emission wavelength of 560 nm is considered in this study. Effects of phosphor concentration, thickness of the conversion medium, excitation spectrum, and driving current are studied in terms of luminous efficacy and the quality of white light emission. It has been observed that the above parameters have a significant effect on chromaticity coordinates. Ray-tracing simulation results show that the luminous efficacy of down-converted white light is found to be 3.25 times the blue light excitation with phosphor concentration of 2.10E7  cm ⁻³ and thickness of 30 μm for an injection current density of 10  A/cm ² . A stable cool white light having correlated color temperature in a range of 5500–5600 K is achieved for the proposed optimized design for the variation of ambient temperatures from −25°C to 150°C.

Platinum-based blue and red emitters were used to make stacked organic light-emitting diodes devices for potential use in solid-state lighting. The electroluminescence (EL) spectra were strongly dependent on the red layer thickness and relative position of the red and blue emissive layers. Although all devices had very little EL in the green region, a color rendering index (CRI) as high as 65 was achieved. Addition of a suitable phosphorescent green emissive layer should produce higher CRI values. All devices tested exhibited external quantum efficiencies greater than 20%, indicating that the Pt-based emitters reported here are potentially useful for solid-state lighting applications.

Candles emit sensationally warm light with a very low color temperature, comparatively most suitable for use at night. In response to the need for such a human-friendly night light, we demonstrate the employment of a high number of candlelight complementary organic emitters to generate and mimic candlelight based on organic light emitting diode (OLED). One resultant candlelight style OLED shows a very-high color rendering index (CRI), with an efficacy at least 300 times that of a candle or at least two times that of an incandescent bulb. The device can be fabricated, for example, by using four candlelight complementary emitters: red, yellow, green, and sky-blue phosphorescent dyes. These dyes, in the present system, can be vacuum deposited into two emission layers that are separated by a nanolayer of carrier modulation material that is used to maximize very high CRI and energy efficiency. A nano carrier modulation layer also played a significant role in maintaining the low blue emission and high-red emission, the low color temperature of device was obtained. Importantly, a romantic sensation giving and supposedly physiologically friendly candlelight style emission can hence be driven by electricity in lieu of hydrocarbon burning and greenhouse gas-releasing candles that were invented 5000 years ago.

Blue to red organic light-emitting diodes based on a series of newly synthesized distyrylbenzenes have been demonstrated. Their optical properties have been theoretically and experimentally studied in order to inquire into the substitution effects (such as electron-donating, electron-withdrawing, and steric hindrance) on the emission color. Density functional theory at B3LYP/6-311+G(d) level of calculation was employed to obtain the molecular structures and highest occupied molecular orbital and lowest unoccupied molecular orbital surfaces. Electroluminescence emission range of compounds could be tuned by changing the strength of the acceptor component and using push–pull and nonplanarity effects from 483 (blue) to 600 (red) nm.

Using a facile method, a compound (alloy) semiconductor from the family of cadmium-zinc-sulfide doped with tin and silver was hydrothermally synthesized and employed as an efficient photocatalyst to generate hydrogen fuel through a water photosplitting system. X-ray diffraction analyses revealed that the alloy semiconductor is a solid solution that becomes crystalized in a cubic structure, having a smaller lattice constant in the presence of Ag dopant. Reflective UV-visible spectra indicated that the Ag component not only causes the photon absorption to be significantly amplified, but the absorption edge also shows a red shift. Scanning electron microscopy and adsorption/desorption isotherms illustrated that the five-component semiconductor synthesized here belongs to the nanostructured (nanoparticulate/nanoflake) mesoporous materials and exhibits a good photocatalytic performance.

In this work, we investigate the use of a picosecond (ps) laser used for monolithic connection to texture three commercially available and frequently used multicomponent glasses, Corning EAGLE XG®, Schott BOROFLOAT® 33 and Saint-Gobain SGG DIAMANT®. The results show that the ablated crater profile and degree of texturing are glass composition dependent. This might be attributed to the different laser-induced electron collision times and recombination rates, and thus the critical electron density evolution leading to ablation. The surface texture is altered from periodic to random with decreasing scribing speed. The transmission of the textured substrates gradually decreases, whereas the multireflection on the surface increases as a consequence of the topological and morphological changes. The angular resolved measurements illustrate that the textured glass substrates scatter the light toward greater angles, which is necessary to increase the effective optical path in the absorber layer. Simulation results show that textured glass increases the absorption in the absorber material and the slightly modified refractive index region around the crater does not counteract the light in-coupling effect. The results suggest that these substrates can be used in various photovoltaic technologies and show potential for the application of alternative front contacts, such as carbon nanotubes.

The solar energy industry strives to produce more efficient and yet cost effective solar panels each consisting of an array of photovoltaic (PV) cells. The goal of this study was to enhance the performance of PV cells through increasing the cells’ optical efficiency defined as a percentage of surface incident light that reaches the PV material. This was achieved through the reduction of waveguide decoupling loss and Fresnel reflection losses by integrating specific nonimaging micro-optical structures on the top surface of existing PV cells. Due to this integration, optical efficiency and performance were increased through the enhancement of light trapping, light guiding, and in-coupling functionalities. Periodic triangular gratings (PTGs) were designed, nonsequentially modeled, optimized, and fabricated in polydimethylsiloxane as proposed micro-optical structures. Then the performance of PV cells with and without integrated PTGs was evaluated and compared. Initial optical simulation results show that an original PV cell (without PTG) exhibits an average optical efficiency of 32.7% over a range of incident light angles between 15 and 90 deg. Integration of the PTG allows the capture of incoming sunlight by total internal reflection (TIR), whence it is reflected back onto the PV cell for multiple consecutive chances for absorption and PV conversion. Geometry of the PTG was optimized with respect to an angle of light incidence of {15, 30, 45, 60, 75, 90} deg. Optical efficiency of the geometrically optimized PTGs was then analyzed under the same set of incident light angles and a maximum optical efficiency of 54.1% was observed for a PV cell with integrated PTG optimized at 90 deg. This is a 53.3% relative improvement in optical performance when compared to an original PV cell. Functional PTG prototypes were then fabricated with optical surface quality (below 10 nm Ra ) and integrated with PV cells demonstrating an increase in maximum power by 1.08  mW/cm² (7.6% improvement in PV performance) and in short circuit current by 2.39  mA/cm² (6.4% improvement).

It is a known rule that the efficiency of thermodynamic solar plants increases with the working temperature. At present, the main limit in temperature upscaling is the absorber capability to withstand high temperatures. The ideal solar absorber works at high temperatures and has both a low thermal emissivity and a high absorptivity in the solar spectral range. The present work reports on the preparation and optical characterization of hafnium and zirconium diboride ultrahigh-temperature ceramics for innovative solar absorbers operating at high temperature. Spectral hemispherical reflectance from the ultraviolet to the mid-infrared wavelength region and high-temperature hemispherical emittance reveal their potential for high-temperature solar applications. Boride samples are compared with silicon carbide (SiC), a material already used in solar furnaces.