Effect of double blocking layers at TiO2/Sb2S3 and Sb2S3/spiro-MeOTAD interfaces on photovoltaic performance

The effect of double blocking layers on the Sb2S3-sensitized all solid state solar cell are investigated. Thin layers of ZrO2 (blocking layer 1, BL1) and ZnS (blocking layer 2, BL2) are introduced at the TiO2/Sb2S3 and Sb2S3/hole transporting material (HTM) interfaces. The presence of BL1 is found to improve the open-circuit voltage (V-oc) from 457 mV to 618 mV, whereas BL2 improves mainly short-circuit current density (J(sc)) from 11.1 mA cm(-2) to 14.0 mA cm(-2). Transient photovoltage confirms that the BL1 efficiently blocks charge recombination, responsible for the V-oc enhancement, whereas the BL2 has little effect on suppression of charge recombination. Surface modification of Sb2S3 by BL2, on the other hand, leads to recovery of Sb2S3 from the surface oxidized Sb2O5, which affects the J(sc) increment. The present results suggest that the TiO2/Sb2S3 interface is the main pathway for charge recombination rather than the Sb2S3/HTM interface. Double blocking layers enhanced the power conversion efficiency by 30%.