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 CuxS / brass as a counter electrode, exhibiting 10.10 mA . cm − 2 short-circuit current density (Jsc), 429-mV open circuit voltage (Voc), 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.
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.