Novel CdS Hole-Blocking Layer for Photostable Perovskite\nSolar Cells

Abstract

Currently, the stability issue of\nthe perovskite solar cells (PSCs)\nis one of the most critical obstacles in the commercialization of\nPSCs. Although incredible advances in the photovoltaic efficiencies\nof PSCs have been achieved in the past few years, research on the\nstability of PSCs has been relatively less explored. In this study,\na new kind of CdS hole-blocking layer replacing the traditional compact\nTiO₂ layer is developed to improve the photostability of\nPSCs because the intrinsic oxygen vacancies of the TiO₂ surface are suspected to be the main cause for the photoinduced\ndegradation of PSCs. As a result, PSCs with the CdS layer exhibit\nconsiderably improved photostability, maintaining over 90% of the\ninitial efficiency after continuous sunlight illumination for 12 h,\nwhile the TiO₂ PSC retains only 18% of the initial efficiency\nunder the same conditions. Charge-transfer characteristics related\nto photodegradation are investigated by various analyses including\nelectrochemical impedance spectroscopy and open-circuit voltage decay\nand time-resolved photoluminescence decay measurements. the CdS PSC\nexhibits negligible degradation in the charge-carrier dynamics, while\nthe TiO₂ PSC suffers from severely damaged characteristics\nlike increased charge recombination rate, charge-transfer resistance,\nand reduced charge extraction rate.