Understanding the effect of antisolvent on processing window and efficiency for large-area flexible perovskite solar cells Cong Chen a, b , Yue Jiang a, ** , Yancong Feng a, *** , Zhuoxi Li a , Nengjie Cao c , Guofu Zhou c , Jun-Ming Liu d , Krzysztof Kempa e , Shien-Ping Feng b, **** , Jinwei Gao a, * a Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, And Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Normal University, Guangzhou, 510006, China b Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Rd., Pokfulam, Hong Kong c Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, 510006, China d Laboratory of Solid-State Microstructures, Nanjing University, Nanjing, 210093, China e Department of Physics, Boston College, Chestnut Hill, MA, 02467, USA article info Article history: Received 15 September 2021 Received in revised form 11 October 2021 Accepted 25 October 2021 Available online 27 October 2021 Keywords: Antisolvent Processing window Large-area Perovskite solar cells abstract One-step method assisted by antisolvent is the most useful strategy to fabricate perovskite solar cells (PSCs) with high power conversion efficiency (PCE). Nevertheless, the narrow processing window and strict solvent ratio limit the preparation of large-area and uniform perovskite films. Herein, by thorough in-depth study of the interaction between solvents and antisolvents in the film preparation process, we found that the typical dimethylformamide solvent plays an important role in the antisolvent washing process. We demonstrate a solvent-antisolvent interaction model to understand the originality of the narrow processing window and solvent ratio based on chlorobenzene. Here, a green antisolvent e Ethyl Methyl Carbonate is introduced to widen a processing window from 2s to 35s and extend the volume ratio of dimethylformamide: dimethyl sulfoxide varying from 7:3 to 0:10 in the precursor solution. The obtained PSCs show a remarkable efficiency of 22.08% on rigid substrates, and 19.14% on flexible sub- strates. In a parallel effort, we demonstrate a uniform and large-area (6  6 cm 2 ) flexible perovskite solar cell, exhibiting the highest PCE of 18.60%. © 2021 Elsevier Ltd. All rights reserved. 1. Introduction Organiceinorganic hybrid perovskite solar cell (PSC) has been intensively investigated as a promising candidate for the next- generation photovoltaic devices, which has provided affordable and clean energy with a certified power-conversion efficiency (PCE) over 25% [1e3]. The significant progress relies on superior inherent properties of perovskite materials such as high absorption coeffi- cient, long carrier lifetime (up to 30 ms), large carrier diffusion length (>1 mm) and low exciton binding energy, as well as various methods of depositing perovskite film including vacuum vapor deposition and one-step/two-step solution deposition technologies [4e9]. Among the above methods, one-step antisolvent assisted solu- tion technology is an effective and widely adopted approach to obtain a dense and highly crystallized solution-processed perov- skite film which is paramount in determining the device perfor- mances [10][e][14]. Antisolvent could extract solute from the precursor, thus forming a driving force towards the formation of intermediate phase from this supersaturated solution [15e19]. The commonly used antisolvents include chlorobenzene (CB) [20], toluene (TL) [16] and diethyl ether (DE) [21]. However, apart from their toxicity, these antisolvents are facing severe problems, including the extremely narrow processing window which is severely relied on two parameters: (1) the ratio of DMF/DMSO needs to be precisely optimized within a narrow range for different antisolvents. For instance, the proper volume ration of DMF/DMSO for antisolvent CB is 4:1 [22], TL is 7:3 [8] and DE is 9:1 [21]; (2) the antisolvent has to be dripped at a specific time slot (8e10th s) after * Corresponding author. ** Corresponding author. *** Corresponding author. **** Corresponding author. E-mail addresses: yuejiang@m.scnu.edu.cn (Y. Jiang), fengyancong@m.scnu.edu. cn (Y. Feng), hpfeng@hku.hk (S.-P. Feng), gaojinwei@m.scnu.edu.cn (J. Gao). Contents lists available at ScienceDirect Materials Today Physics journal homepage: https://www.journals.elsevier.com/ materials-today-physics https://doi.org/10.1016/j.mtphys.2021.100565 2542-5293/© 2021 Elsevier Ltd. All rights reserved. Materials Today Physics 21 (2021) 100565