Ag2S quantum dot-sensitized WO3 photoelectrodes for solar cells

This work investigates the photovoltaic properties of new-architecture Ag₂S quantum dot-sensitized solar cells (QDSCs) fabricated on WO₃ electrodes. Liquid-junction Ag₂S QDSCs were fabricated from QDs synthesized using the successive ionic layer adsorption and reaction process. The optimal QDSC yielded an efficiency η of 0.20 % under a 100-mW/cm² light illumination. Coating the QDSC with a compact layer and a scattering layer improved η to 0.31 % with a short-circuit current density J _sc of 5.81 mA/cm² and an open-circuit voltage V _oc of 0.21 V. η increased to 0.53 % at a reduced 0.1 sun illumination with a J _sc of 1.11 mA/cm². The external quantum efficiency (EQE) spectrum covered the spectral range of 350–900 nm with a maximal EQE of 29 % at λ?=?650 nm. This work demonstrates the feasibility of the new-configuration Ag₂S QDSCs fabricated on WO₃ electrodes.     

ZnO nanorods on undoped and indium-doped ZnO thin films as a TCO layer on nonconductive glass for dye-sensitized solar cells

We present the growth of ZnO nanostructures on indium-doped ZnO film on a non-conductive glass substrate. The indium-doped ZnO film was used as the transparent conductive layer replaces the ITO layer. Various indium doping concentrations can change the electrical properties of ZnO film. The reduced electrical resistivity was investigated from 16.60 × 10⁻² to 10 × 10⁻² Ω cm. after doping with the optimal concentration of 2 wt% indium. It is found that the characteristic of ZnO nanostructures was strongly affected with indium doping concentration in ZnO films. The overall structural characteristics of ZnO ranged from 100–500 nm in size and 7–10 μm in length and the branch-like structures can be revealed from the 2 wt% indium-doped ZnO film. The room-temperature photoluminescence spectra show a sharp ultraviolet band of 353 nm, indicated to the ZnO nanorods structure. The branch-like structures on the 2 wt% indium-doped film can be yielded the photovoltaic properties with a short-circuit current density of 3.96 mA/cm², an open-circuit voltage of 0.72 V, a fill factor of 20% and an overall power conversion efficiency of 0.56% under irradiance of 100 mW/cm² (AM 1.5 G).     

Ag2S quantum dot-sensitized solar cells

We present a new photosensitizer – Ag₂S quantum dots (QDs) – for solar cells. The QDs were grown by the successive ionic layer adsorption and reaction deposition method. The assembled Ag₂S-QD solar cells yield a best power conversion efficiency of 1.70% and a short-circuit current of 1.54 mA/cm² under 10.8% sun. The solar cells have a maximal external quantum efficiency (EQE) of 50% at λ = 530 nm and an average EQE of ～ 42% over the spectral range of 400–1000 nm. The effective photovoltaic range covers the visible and near-infrared spectral regions and is ～ 2–4 times broader than that of the cadmium chalcogenide systems — CdS and CdSe. The results show that Ag₂S QDs can be used as a highly efficient and broadband sensitizer for solar cells.     

Zinc oxide nanostructures for applications as ethanol sensors and dye-sensitized solar cells

ZnO nanostructures were prepared by thermal oxidation technique for applying as ethanol sensors and dye-sensitized solar cells. To improve sensitivity of the sensor based on ZnO nanostructures, gold doping was performed in ZnO nanostructures. Gold-doped with 0%, 5%, and 10% by weight were investigated. The improvement of sensor sensitivity toward ethanol due to gold doping was observed at entire operating temperature and ethanol concentration. The sensitivity up to 145 was obtained for 10% Au-doped ZnO sensor. This can be explained by an increase of the quantity of oxygen ion due to catalytic effect of gold. Also, it was found that oxygen ion species at the surface of the Au-doped ZnO sensor remained O²⁻ as pure ZnO sensor. For dye-sensitized solar cell application, the dye-sensitized solar cell structure based on ZnO as a photoelectrode was FTO/ZnO/Eosin-Y/electrolyte/Pt counter electrode. ZnO with different morphologies of nanobelt, nano-tetrapod, and powder were investigated. It was found that DSSCs with ZnO powder showed higher photocurrent, photovoltage and overall energy conversion efficiencies than that of ZnO nanobelt and ZnO nano-tetrapod. The best results of DSSCs were the short circuit current (J_sc) of 1.25 mA/cm², the open circuit voltage (V_oc) of 0.45 V, the fill factor (FF) of 0.65 and the overall energy conversion efficiency (η) of 0.68%.