Enhancement in Photovoltaic Performance of Solar Cells by Electrostatic Adsorption of Dyes on ZnO Nanorods.

ZnO nanorods were formed by chemical bath deposition on fluorine-doped tin oxide (FTO) glass and the photovoltaic performance of ZnO-based dye-sensitized solar cells (DSCs) was investigated. A DSC with 8 h-grown ZnO nanorods showed a higher power conversion efficiency (PCE) than devices with 4, 6, and 10 h-grown ones. Further improvement in PCE was achieved in a cell with a silver-ion-deposited ZnO/FTO electrode. By deposition of Ag+ on the surface of the 8 h-grown ZnO nanorods, the dye-loading amount increased by approximately 210%, compared to that of pristine ZnO nanorods, resulting in a 1.8-times higher PCE. A DSC with the pristine ZnO/FTO electrode showed a PCE of 0.629%, while in a device with the silver-ion-deposited ZnO/FTO, the PCE increased to 1.138%. In addition, interfacial resistance at the ZnO/dye/electrolyte was reduced to approximately 170 Ω from 460 Ω for the control cell with the pristine ZnO/FTO. We attributed the higher dye-loading amount in the silver-ion-deposited ZnO/FTO to the electrostatic attraction between the positively charged ZnO and carboxylate anions (-COO-) of the N719 dyes.

Molecular Weight Effects of Biscarbazole-Based Hole Transport Polymers on the Performance of Solid-State Dye-Sensitized Solar Cells.

The leakage and volatilization of liquid electrolytes limit the commercialization of dye-sensitized solar cells (DSCs). As solid-state (ss) hole-transporting materials, free from leakage and volatilization, biscarbazole-based polymers with different molecular weights (PBCzA-H (21,200 g/mol) and PBCzA-L (2450 g/mol)) were applied in combination with additives to produce ssDSCs. An ssDSC with PBCzA-H showed a better short-circuit current (Jsc), open-circuit voltage (Voc), and fill factor (FF) than a device with PBCzA-L, resulting in 38% higher conversion efficiency. Compared to the PBCzA-L, the PBCzA-H with a higher molecular weight showed faster hole mobility and larger conductivity, leading to elevations in Jsc via rapid hole transport, Voc via rapid hole extraction, and FF via lowered series and elevated shunt resistances. Thus, it is believed that PBCzA-H is a useful candidate for replacing liquid electrolytes.