Good quality cadmium sulfide/cadmium selenide (CdS/CdSe)-based ZnO nanorods photoanodes were successfully prepared from ZnO nanorods electrochemically grown on fluorine-doped tin oxide glass substrates. The photoanodes worked as electrodes and zinc nitrate hexahydrate-based solution as electrolyte, followed by a CdS/CdSe sensitization by a SILAR method, for application in quantum dots sensitized solar cells (QDSSCs). The performance of the QDSSC was optimized by control of the synthesis temperature of ZnO nanorods and the annealing process, the number of SILAR cycles, and the use of different counter electrodes (brass or copper thin film). The optimized QDSSC was prepared with ZnO nanorods grown at 90°C, annealed at 300°C, and cosensitized by CdS/CdSe with 16 and 8 SILAR cycles, respectively, and Cu_xS  /  brass as a counter electrode, exhibiting 10.10  mA  .  cm^−  2 short-circuit current density (J_sc), 429-mV open circuit voltage (V_oc), and 1.23% power conversion efficiency.

Solution-processed small molecule-based solar cells have demonstrated high power conversion efficiencies in recent years. However, several challenges have yet to be overcome, including achieving of low cost and excellent long-term stability of donor small molecules. Therefore, development of stable blocks to design organic semiconductors with optimal properties remains an actual problem. We report an alkyl-free star-shaped donor–acceptor (D–A) molecule, N(Ph-2T-DCV-PhF)₃, containing p-fluorophenyldicyanovinyl (FPh-DCV) electron-withdrawing groups, triphenylamine as the donor core, and 2,2′-bithiophenes as the π-bridges between them. The study of thermal, optical, and electrochemical properties of the molecule in comparison to the direct analog with phenyldicyanovinyl groups, N(Ph-2T-DCV-Ph)₃, made it possible to demonstrate the effect of the fluorine substituent on such key parameters as solubility, bandgap, lowest unoccupied molecular orbital energy level, phase behavior, thermal stability, and wettability. This work suggests that usage of the FPh-DCV block is an effective and simple tool to tune physical and physicochemical properties of stable D–A small molecules.

A theoretical study is presented on planar micro-optic solar concentrators. These can be inexpensively fabricated using nanoimprinting techniques and can provide indoor illumination. Multiple combinations of lenslet array designs and coupling features are optimized, and full system efficiencies are evaluated by ray-tracing simulations. Concentrator designs are optimized with considerations of suitability to tropical regions. A design capable of near-unity efficiency at up to 18-deg field angles and up to 92.14% collection efficiency within ±30-deg incident angle is reported. A cost analysis is then performed using meteorological data.

Spatial distribution of the photogenerated carriers in a hydrogenated microcrystalline silicon (μc-Si  :  H) solar cell has a significant impact on its electrical characteristics. Photogeneration distribution can be manipulated using photon management techniques. The electrical specifications of a typical thin-film μc-Si  :  H solar cell under various distributions of photocarriers are thoroughly investigated for both zero and higher bias voltages. For a thin-film μc-Si  :  H solar cell with a typically low thickness, we conclude that a photogeneration distribution having a greater rate in the central region of the solar cell performs optimally. This result is in contrast to the previously reported results in the literature for some other thin-film solar cell technologies, where the improved performance of a thin-film solar cell is believed to be when the photogenerated carriers are concentrated near the anode. It is demonstrated that the dominant contribution of dark carriers to recombination in the middle of the cell at higher bias voltages causes this effect. Moreover, we propose a lens-like structure by patterning top layers of a μc-Si  :  H solar cell, which approximately realizes the desired photogeneration distribution and provides an increase in the density of photocarriers in the middle of the solar cell, while it also acts as an antireflection coating. This proposed configuration has a 1.3% improvement in power conversion efficiency compared with a planar μc-Si  :  H solar cell with identical constituting layers and similar dimensions.

The chemical bath deposited n-type CdS and Cd(S,O) layer were implemented as electron transport (ET) layers integrated with ZnO hole blocking (HB) layer in the fabrication of planar CH₃NH₃PbI₃ (MAPbI₃) perovskite solar cells (PSC). The bonding environment and native defect structure of CdS and Cd(S,O) ET layers were established by Raman and photoluminescence spectral analysis. Optical studies showed that Cd(S,O) has higher UV–Vis transmittance and band edge threshold relative to CdS of similar thickness. The photovoltaic performance of the solar cells evaluated with CdS and Cd(S,O) ET layers of different 40-, 55-, and 80-nm thickness shows the effect of light intensity at the MAPbI₃ photoabsorber and establishes the importance of native defects in electron extraction and transport in determining photoconversion efficiency (PCE). The effect of defect states in CdS and Cd(S,O) over corresponding J–V curves and fill factor of PSC device are described in terms of an energy band model. For 40-nm-thick Cd(S,O)/ZnO (ET/HB) layer, a PCE of 11.1% was achieved and compared with 9.18% for the CdS/ZnO (ET/HB) layer.

The spectrum of 400 to 1100 nm sunlight can be divided into three bands, each absorbed by organic photovoltaic devices that are particularly efficient under the band in question, to achieve higher photoelectric conversion efficiency. The three bands are the absorption bands of fullerene (C₇₀), chloroaluminum phthalocyanine (ClAlPc), and tin naphthalocyanine dichloride (SnNcCl₂), which have peak values of 500, 731, and 863 nm, respectively. C₇₀ is a well-known acceptor, whereas ClAlPc and SnNcCl₂ serve as donors. In combination with another donor made of 4,4’-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (TAPC), which is almost transparent in 400 to 1100 nm, three devices were fabricated and had active layers of TAPC  :  C₇₀, ClAlPc  :  C₇₀, and SnNcCl₂  :  C₇₀. After the doping proportions of these materials had been optimized, the maximum power conversion efficiency (PCE) values of the three devices were 4.52%, 4.3%, and 1.33%, respectively. The properties of donor material dominated the differences among these device behaviors. Subsequently, the overall PCE of a simulated multiple reflection module was calculated using these three devices, which, depending on the arranged sequence in which they were exposed to light and reflected the light to another, generated different absorption spectrum and thus influenced the overall PCE of the photovoltaic integrator. The highest overall simulated and experimental PCE of the photovoltaic integrator was 6.12% and 5.9%, respectively.

The properties of luminescence coupling (LC) in multijunction solar cells were investigated in three-terminal InGaP//InGaAsP and InGaP/GaAs//InGaAsP tandem solar cells fabricated using the bonding technique through metal nanoparticle (MNP) arrays, where // denotes the mechanical stacking using MNP arrays. Power extraction in the three-terminal tandem solar cells is evaluated, showing that the power extraction in the devices is equivalent to a sum of the power extraction of the top and bottom subcells. In addition, the properties of the LC effect are investigated in the three-terminal tandem devices. The LC current increases with the illuminated light intensity and shows a bias-voltage dependency of the subcell that is emitting luminescence. We also discuss the impact of LC on the power extraction of the three-terminal tandem solar cells.

Mechanically stacked tandem solar cells are a potential near-term solution for increasing the efficiency of photovoltaic modules. Practical implementation requires an interconnection approach that maximizes efficiency and minimizes complexity and cost. Connecting the top and bottom cells in a voltage-matched configuration allows two-terminal modules to be fabricated without altering the cell design or processing methods. Here, we experimentally demonstrate two-terminal voltage-matched GaInP₂  /  Si minimodules. The two-terminal minimodules performed just as well as four terminal configurations when voltage-matching requirements were met. The magnitude of the efficiency loss experienced by the voltage-matched minimodule when voltage-matched conditions were not met depends on whether the voltage was constrained by the GaInP₂ or Si cells. Monte Carlo simulations also indicate that the two-terminal voltage-matched tandems respond to small cell-to-cell parameter variations in a similar manner as four terminal tandems.

A series of 2,6-bis-styryl-4H-pyran-4-ylidene fragment containing glass-forming organic compounds with bonded amorphous phase promoting bulky triphenyl moieties through piperazine structural fragment [2-(2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-pyran-4ylidene)malononitrile derivatives (DWK)-T dyes] in a form of (5,5,5-triphenylpentyl)piperazin-1-yl)styryl)-substituent attached to the 4H-pyran-4-yliden fragment in two-position have been synthesized and investigated as the potential light-amplification medium for organic solid-state lasers. DWK-T dye physical properties also depend on the structure of the other styryl-substituent attached to the 4H-pyran-4-ylidene backbone fragment in six-position. Thermal stability of synthesized dyes is above 312°C with the glass transitions from 97°C and up to 109°C. Obtained neat pure spin-cast films based on these compounds show photoluminescence with λ_max in range from 672 to 695 nm, ASE λ_max from 690 to 704 nm with ASE threshold values in range from 327 to 1091  μJ  /  cm², which are mostly influenced by the nature of the electron transition characteristics of various four substituents in a 6-styryl-fragment. The proposed synthetic approach could be useful for obtaining chemically stable and covalently bonded bulky triphenyl group containing glassy dyes, while the synthetic design allows to acquire different nonsymmetric 2,6-bis-styryl-4H-pyran-4-ylidene fragment-containing compounds for red and infrared light-emitting and light amplification applications.

We introduce a simple and low-cost approach—drop-coating method—for preparation of in-situ self-assembled perovskite nanocrystals for efficient light-emitting diodes (LEDs). The photoluminescence (PL) spectrum of the self-assembled NFPI₄ nanocrystals thin film prepared by the drop-coating method shows blue shift compared with that of the typical NFPI₄ thin film prepared by the spin-coating method. In addition, the PL spectra of these self-assembled nanocrystals are tuned from 765 to 725 nm by changing usage amounts of the perovskite precursor solution. More importantly, efficient LEDs with external quantum efficiencies up to 6.8% are achieved based on these self-assembled NFPI₄ nanocrystals.

The optical characteristics of a star-shaped silicon nanowires (Si NWs) solar cell (SC) are numerically studied using three-dimensional (3-D) finite-difference time-domain (FDTD). The particle swarm optimization technique is used to optimize the geometrical parameters of the NW to maximize its light absorption. The optimized star-shaped Si NWs offer high ultimate efficiency (η) of 43.7% while its complementary design achieves η of 40.1%. This is due to the star surface textures that allow multiple light scattering between the NWs. This will increase the optical path length through the NW and improve its light absorption. The electrical properties of the proposed design are also calculated using the finite-element method. In this investigation, the doping level of the star-shaped Si NWs with p  −  i  −  n axial and radial configurations is simulated to quantify the optoelectronic performance of the reported design. The p  −  i  −  n axial doped design offers power conversion efficiency (PCE) of 21%; however, the p  −  i  −  n radial doping gives PCE of 21.3%. Therefore, the star-shaped design violates PCE of 17.3% and 15.9% of the conventional Si NWs with axial and radial doping, respectively.