Stabilization of Component-Pure α‑FAPbI3 via Volatile Additives for Stable Photovoltaics

• Published in: ACS applied materials & interfaces 2023-04, Vol.15 (13), p.16818-16827
• Main Authors: Wang, Dianxi, Chen, Muyang, Zhang, Xuecong, Chao, Lingfeng, Niu, Tingting, Lv, Yifan, Xing, Guichuan, Xia, Yingdong, Li, Mingjie, Zhang, Hui, Chen, Yonghua
• Format: Article
• Language: English
• Subjects: ammonium acetate; Energy, Environmental, and Catalysis Applications; heat tolerance; hydrogen; lighting; solar energy
• ISSN: 1944-8244; 1944-8252; 1944-8252
• DOI: 10.1021/acsami.3c01973

State-of-the-art high-performance perovskite solar cells are mainly based on formamidinium (FA)-dominated perovskites because of their narrow band gap and remarkable thermal resistance. However, photoactive α-FAPbI3 is prone to transit to the photoinactive phase, and pioneering phase stabilization strategies can induce undesirable band gap broadening or phase segregation, seriously restricting the efficiency and long-term stability of the resultant photovoltaics. Herein, a small molecule of ammonium acetate (NH4Ac) was introduced as an additive in a modified ripening method to fabricate component-pure α-FAPbI3. Owing to the strong interaction between NH4Ac and PbI2, FAI via Pb–O coordination, and N–H···N hydrogen bonding, vertically oriented perovskites with relaxed crystal strain were first generated, which were fully converted to α-FAPbI3 in a further ripening process. The NH4Ac was fully volatized after the perovskite formation, resulting in component-pure α-FAPbI3 with a band gap of 1.48 eV and remarkable stability under light illumination. Ultimately, a champion device efficiency of above 21% was obtained based on the component-pure α-FAPbI3 and over 95% of the initial efficiency can be maintained after 1000 h of aging.