A universal surface fixed charge reconstruction strategy to minimize contact loss in wide bandgap perovskite photovoltaics

Abstract

It is widely accepted that non-radiative recombination losses in the wide-bandgap (WBG) subcell dominate carrier recombination processes in perovskite tandem photovoltaics. We demonstrate that healing the perovskite top surface with an additive, potassium thioglycolate, inhibits Pb–Pb dimer formation at the top surface, which is particularly important for ultra-WBG perovskites Cs_xFA_1−xPb(I_1−yBr_y)₃ (y > 0.6). Concurrently, field effect passivation, induced by the ordered arrangement of linear diamine 1,3-diammonium and associated adequate surface fixed charge, is reconstructed. This “healing–reconstruction” strategy suppresses cross-interface recombination and increases the open circuit voltage (V_OC), delivering the highest V_OC value reported to date for the 1.91 eV perovskite. The strategy allows us to approach the potential of V_OC (with V_OC losses of <10% of the SQ limit) in single-junction applications employing band gaps in the range of 1.6 to 1.9 eV, which is critical for tandem solar cells.