Accelerating direct formation of α-FAPbl3 by dual-additives synergism for inverted perovskite solar cells with efficiency exceeding 26 %

Abstract

Improving the efficiency of inverted perovskite solar cells (PSCs) is crucial for promoting their commercialization. The α-FAPbI₃ shows huge promise as an absorber, however, its unfavored energetically at room temperature make the preparation of high-quality α-FAPbI₃ a challenge. In this work, the dual-additives were utilized to enhance the phase purity of α-FAPbI₃, and the underlined synergism was revealed. Both experimental measurement and theoretical calculation conformed that the dual-additives of MACl and PbCl₂ can synergistically enhance the ability to accelerate the direct formation of α-FAPbI₃ through largely reducing its formation energy, and inhibit the undesired δ-phase that inevitably occurs neither which additive is utilized singly. This synergism of dual-additives supports to realize a high-quality perovskite films with enhanced phase purity, and reduced defect density. As a consequence, the inverted PSCs achieve an impressive efficiency of 26.17 %, and the unencapsulated device can maintain 93 % of their initial PCE after 2000 h of storage in ambient air at 20 % RH and 25 ± 5 °C.