Synergy of Front‐Surface Energy‐Level Gradient and Lattice Anchoring Effect for Enhancing Perovskite Solar Cell Performance

Abstract A front surface gradient of the absorber valence band can effectively reduce the open‐circuit voltage (V_OC) loss of perovskite solar cells by suppressing the minority carrier concentration near the front surface. However, the existing method is limited to the one‐step fabrication process, resulting in underachieved photon harvesting and power conversion efficiency (PCE). To solve the problem, ZnCd‐based alloy quantum dots (QDs) are utilized to create a valence‐band‐maximum gradient at the front surface of a two‐step processed FAPbI₃ absorber. This design significantly enhances V_OC without requiring surface passivation. Furthermore, it is demonstrated that reducing the QD‐perovskite lattice mismatch while maintaining QD's energy levels mitigates nonradiative recombination without compromising the front surface gradient effect. As a result, normal‐structured perovskite solar cells achieve a V_OC equivalent to 93% of the Schockley–Queisser limit and a PCE of 24.37%.