New strategy for improving the perovskite solar cells’ open-circuit voltage: Cation substitution of hole transport layer

Abstract It has been proven that both recombination and band gap difference are the key issues responsible for Voc enhancement, and a wide band gap inorganic hole-transporting material (HTM) is more favorable for efficient perovskite solar cells. Herein, we employed the wide band gap CuGaS2 (CGS) quantum dots (QDs) as HTM. And such quantum dots were used in novel solar cells based on perovskite materials though the method of cation substitution. Through substitution of indium element with gallium element, band gap of the QDs was changed greatly (from 1.56 eV to 2.29 eV). The processes of charge transfer and the alignment of band level were studied in details and the result indicates that the increase of conduction band level for CGS with wide band gap led to a dramatic increase in Voc. And the cell efficiency was finally improved from 10.46% to 12.78%.