Precisely Tuning 3D/Quasi‐2D Perovskite Heterojunctions in Wide‐Bandgap Perovskites for High‐Performance Tandem Solar Cells

Abstract

Abstract Wide‐bandgap (WBG) perovskite sub‐cells in all‐perovskite tandem solar cells (AP‐TSCs) suffer from severe open‐circuit voltage loss and poor light stability. The formation of 3D/2D or 3D/quasi‐2D perovskite heterojunctions can effectively passivate interface defects and optimize energy level alignments at the 3D perovskite/C 60 interface, thereby enhancing both the efficiency and stability of perovskite solar cells. Herein, a combined evaporation/solution technique is employed to construct Dion‐Jacobson (DJ) 2D or quasi‐2D perovskites with uniform‐phase distribution on wide‐bandgap 3D perovskite substrates. By tuning the n values of the DJ phase perovskites, well‐refined WBG 3D/2D or quasi‐2D perovskite heterostructures are achieved, which exhibit tunable energy levels and mitigate the non‐radiative recombination losses at the WBG 3D perovskite/C 60 interface. The devices with the WBG (1.78 eV) 3D/quasi‐2D n = 3 perovskite heterostructures achieve the champion power conversion efficiency (PCE) of 20.71% (certified 20.53%). When combined with narrow‐bandgap (NBG) perovskite sub‐cells, the fabricated 2‐terminal AP‐TSCs achieve a PCE of 28.99% (certified 28.81%). The tandem device maintains 80% of its initial PCE after 501 h of operation at maximum power point.