Chlorine-conducted defect repairment and seed crystal-mediated vapor growth process for controllable preparation of efficient and stable perovskite solar cells†
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 MaPbI3−xClx 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 (Voc) 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.