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Suppression of charge recombination is an efficient strategy capable of improving the photovoltaic performance of dye-sensitized solar cells (DSSCs). Herein, we fabricate a Nb2O5 thin film on a fluorine-doped tin oxide (FTO) photoanode using a facile dip-coating method and study its blocking effect on charge recombination under various illuminance. The results show that the blocking effect of Nb2O5 is strongly illuminance intensity dependent. The blocking effect of Nb2O5 is insignificant at strong (one sun, >100,000 lux) illumination because the suppressed reverse charge flux makes no substantial contribution to the high-level injection of photo-excited charges. Conversely, the blocking effect plays an important role in the efficiency improvement as the photon-injected charge flux significantly reduces at low-intensity illumination (300-6000 lux). The efficiency of DSSCs with a blocking layer can be improved by 10% to 53% under low-intensity illumination, and the efficiency improvement is attributed to an improvement in fill factor. [ABSTRACT FROM AUTHOR]

Herein, the energy level alignment and electron recombination kinetics in solid state dye-sensitized solar cells (DSCs) employing a solid polymer electrolyte (SPE) have been quantitatively characterized. In order to determine the microscopic origin of the enhanced characteristics in polymer electrolytes, we carried out an extensive study of the photovoltaic properties with respect to the electrolyte type and composition, including a liquid electrolyte (LE) and various salt types and concentrations. We observed a smaller downward shift in the conduction band energy of the TiO 2 layer upon contact with the SPE as well as a retarded electron recombination rate. These led to an increase in the V oc for DSCs with an SPE, which is mostly attributable to the coordinative interactions of the ethylene oxide (EO) units in poly(ethylene oxide) (PEO) and poly(ethylene glycol) dimethyl ether (PEGDME) with metallic Li + ions and Ti atoms. Such coordinative interactions induce 1) the capture of Li + cations in the bulk of the polymer electrolyte, thereby reducing their effective concentration and 2) the facile formation of a PEO passivation layer on top of the TiO 2 layer. Therefore, it was concluded that the high V oc in solid state DSCs employing a polymer electrolyte is attributable to the coordinative properties of the EO units in PEO and PEGDME in the SPE. [ABSTRACT FROM AUTHOR]