2,2-Azodi(2-Methylbutyronitrile)-coordinated Intermediate Phase Engineering for Efficient and Stable Perovskite Solar Cells.

Sequential deposition has been widely employed to modulate the crystallization of perovskite solar cells because it can avoid the formation of nucleation centers and even initial crystallization in the precursor solution. However, challenges remain in overcoming the incomplete and random transformation of PbI 2 films with organic ammonium salts. Herein, a unique intermediate phase engineering strategy has been developed by simultaneously introducing 2,2-Azodi(2-Methylbutyronitrile) (AMBN) to both PbI 2 and ammonium salt solutions to regulate perovskite crystallization. AMBN not only coordinated with PbI 2 to form a favorably mesoporous PbI 2 film due to the coordination between Pb 2+ and the cyano group (CࣽN), but also suppressed the vigorous activity of FA + ions by interacting with FAI, leading to the full PbI 2 transformation with the preferred orientation. Therefore, perovskites with favorable facet orientations were obtained, and the defects were largely suppressed owing to the passivation of uncoordinated Pb 2+ and FA + . As a result, a champion power conversion efficiency over 25% with a stabilized efficiency of 24.8% was achieved. Moreover, the device exhibited an improved operational stability, retaining 96% of initial power conversion efficiency under 1000-h continuous white light illumination with an intensity of 100 mW cm -2 at approximately 55°C in N 2 atmosphere. This article is protected by copyright. All rights reserved.