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Perovskite solar cells (PSCs) have attracted significant research efforts due to their remarkable performance. However, most perovskite films are prepared by the antisolvent method which is not suitable for practical applications. Herein, a (FA_0.83MA_0.17)_0.95Cs_0.05Pb(I_0.83Br_0.17)₃(CsFAMA) perovskite film fabrication technique is developed using solvent volatilization without any antisolvents. The films are formed through recrystallization via the intermediate phase CsMAFAPbI_xCl_yBr_zduring annealing, leading to high‐quality perovskite films. The perovskite growth mechanism is investigated in terms of controlling the amount of formamidinium iodide and methylammonium chloride in the precursor solutions. The oriental growth of the films via the intermediate phase is confirmed by the grazing‐incidence wide‐angle X‐ray scattering measurements. The photovoltaic properties of the perovskite films are investigated. The PSCs based on the films fabricated using the method exhibit a high efficiency of 20.6%. The method developed in this work is based on solvent volatilization, which exhibits significant potential in high reproducibility, facile operation, and large‐scale production. 

Abstract Donor–acceptor (D–A) type semiconducting polymers have shown great potential for the application of deformable and stretchable electronics in recent decades. However, due to their heterogeneous structure with rigid backbones and long solubilizing side chains, the fundamental understanding of their molecular picture upon mechanical deformation still lacks investigation. Here, the molecular orientation of diketopyrrolopyrrole (DPP)‐based D–A polymer thin films is probed under tensile deformation via both experimental measurements and molecular modeling. The detailed morphological analysis demonstrates highly aligned polymer crystallites upon deformation, while the degree of backbone alignment is limited within the crystalline domain. Besides, the aromatic ring on polymer backbones rotates parallel to the strain direction despite the relatively low overall chain anisotropy. The effect of side‐chain length on the DPP chain alignment is observed to be less noticeable. These observations are distinct from traditional linear‐chain semicrystalline polymers like polyethylene due to distinct characteristics of backbone/side‐chain combination and the crystallographic characteristics in DPP polymers. Furthermore, a stable and isotropic charge carrier mobility is obtained from fabricated organic field‐effect transistors. This study deconvolutes the alignment of different components within the thin‐film microstructure and highlights that crystallite rotation and chain slippage are the primary deformation mechanisms for semiconducting polymers.