Enhanced Photovoltage for Inverted Perovskite Solar Cells Using Delafossite CuCrO₂ Hole Transport Material

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 CuCrO _2 nanoparticles synthesized through hydrothermal method was employed as an alternative HTM for triple cation perovskite (FAPbI _3 ) _0.87 (MAPbBr _3 ) _0.13 _0.92 (CsPbI _3 ) _0.08 (possessing better photovoltaic performance and stability than conventional CH _3 NH _3 PbI _3 ) 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 CuCrO _2 HTM. Ultraviolet photoemission spectroscopy demonstrates the energy band alignment between CuCrO _2 and perovskite is better than that between PEDOT: PSS and perovskite, the electrochemical impedance spectroscopy indicates CuCrO _2 -based PSCs exhibit larger recombination resistance and longer charge carrier lifetime than PEDOT: PSS-based PSCs, which contributes to the high V_\rmOC of CuCrO _2 HTM-based PSCs.