Enhanced photovoltage for inverted perovskite solar cells using delafossite CuCrO2 hole transport material

Abstract

Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) has been widely adopted as hole transport material (HTM) in inverted perovskite solar cells (PSCs), due to high optical transparency, good mechanical flexibility, and high thermal stability; however, its acidity and hygroscopicity inevitably hamper the long-term stability of the PSCs and its energy level does not match well with perovskite materials with a relatively low open-circuit voltage. In this work, p-type delafossite CuCrO2 nanoparticles synthesized through hydrothermal method was employed as an alternative HTM for triple cation perovskite [(FAPbI3)0.87(MAPbBr3)0.13]0.92(CsPbI3)0.08 (possessing better photovoltaic performance and stability than conventional CH3NH3PbI3) based inverted PSCs. The average open-circuit voltage of PSCs increases from 908 mV of the devices with PEDOT:PSS HTM to 1020 mV of the devices with CuCrO2 HTM. Ultraviolet photoemission spectroscopy demonstrates the energy band alignment between CuCrO2 and perovskite is better than that between PEDOT:PSS and perovskite, the electrochemical impedance spectroscopy indicates CuCrO2-based PSCs exhibit larger recombination resistance and longer charge carrier lifetime than PEDOT:PSS-based PSCs, which contributes to the high VOC of CuCrO2 HTM-based PSCs.