Achieving a high open-circuit voltage of 1.339 V in 1.77 eV wide-bandgap perovskite solar cells via self-assembled monolayers

Abstract

Severe open-circuit voltage (V_OC) loss significantly hinders the performance improvement of wide-bandgap (WBG) perovskite solar cells (PSCs) and their application in perovskite-based tandem devices. Herein, we develop a novel self-assembled monolayer of (4-(5,9-dibromo-7H-dibenzo[c,g]carbazol-7-yl)butyl)phosphonic acid (DCB-BPA) as the hole-selective layer for WBG PSCs with a 1.77 eV perovskite absorber. DCB-BPA facilitates the subsequent growth of WBG perovskite with improved buried-interface quality. Compared with that of poly(triarylamine) PTAA-based control devices, a substantially enhanced average V_OC from 1.18 V to 1.31 V of DCB-BPA-based devices has been realized due to reduced interfacial nonradiative recombination and enhanced energy level alignment. Our certified device delivers an impressive V_OC of up to 1.339 V and a power conversion efficiency (PCE) of 18.88%, corresponding to a very low V_OC loss of 431 mV (with respect to the bandgap). This enables us to fabricate efficient 4-terminal all-perovskite tandem solar cells with a PCE of 26.9% by combining with a 1.25 eV low-bandgap PSC, demonstrating the promising application of DCB-BPA in tandem devices.