Chlorine-conducted defect repairment and seed crystal-mediated vapor growth process for controllable preparation of efficient and stable perovskite solar cells

Abstract

Currently, chlorine (Cl)-incorporated perovskite solar cells (PSCs) have triggered a strong interest due to their excellent crystallinity and charge transport property. Herein, we present a facile MaCl-assisted (Ma = CH₃NH₃) sequential tubular chemical vapor deposition (STCVD) method to fabricate perovskite films, and report for the first time novel Cl-conducted defect repairment and seed crystal-mediated vapor growth behavior. Further studies indicate that Cl has an ultra-strong reaction capacity and special grain refining ability, and these unique features can effectively heal the inherent ditch defects on PbI₂ templates and overcome the blocking issue of incomplete conversion in perovskites. With the aid of Cl, the well-defined MaPbI_3−xCl_x small seed crystals are obtained and then grow up into compact, crack-free, and highly uniform MaPbI₃ layers with large grain size up to the microscale. Accordingly, the big open-circuit voltage (V_oc) exceeding 1.0 V and high efficiency of 13.76% of our STCVD-processed PSCs measured without aperture mask are successfully achieved in this work. Strikingly, our perovskite device without encapsulation still has an efficiency of 4.15% even after exposure to the ambient conditions for 1152 hour. Overall, we propose a viable strategy to realize the controllable preparation of PSCs, and also disclose the exact role of Cl in film morphology evolution during the gas–solid (G–S) growth process.