Additive engineering in spray enables efficient methylammonium-free wide-bandgap perovskite solar cells

Spray coating is an emerging technique, paving the way for the commercialization of perovskite . However, it still faces challenges in the preparation of wide-bandgap (WBG) perovskite solar cells (PSCs) for tandem photovoltaic devices . Applying a two-step evaporate-spray method, and an additive engineering strategy, where n-propylammonium chloride is introduced in spray processing, we fabricate efficient and stable methylammonium-free (MA-free) WBG PSCs. The propylammonium cation plays a role in passivating grain boundaries, which resulted in the reduction of vacancy defects on the surface of films. Cl − plays a big part in the crystal growth process. After the addition of PACl, preferred crystalline orientation, larger grain size, and reduced trap density in perovskite films are obtained. Finally, the champion WBG PSC (Energy gap (E g ), E g  ≈ 1.68 eV) delivers a power conversion efficiency (PCE) over 19%, which is the highest efficiency of the WBG PSCs prepared by the evaporate-spray method, as compared to pristine devices with the highest PCE of 16.59%. Additionally, the barrier against moisture formed at the surface of films significantly enhances humidity stability of the photovoltaic (PV) device.