Growth Engineering of CH₃NH₃PbI₃ Structures for High‐Efficiency Solar Cells

Controlling the growth of perovskite crystals has been one of the interesting strategies to mold their fundamental properties and exploit their potential in the fabrication of high performance solar cells. Herein, the impact of chloride on the conversion of lead halide into CH₃NH₃PbI₃, morphology, and coverage of perovskite structures using modified two‐step approach is investigated systematically, which eventually dictates the overall performance of the resulting device. Structural and morphological characterization is thoroughly carried out by X‐ray diffraction and field emission scanning electron microscopy, respectively. Various spectroscopic techniques provide ample evidence that CH₃NH₃PbI₃ structures formed in the presence of chloride, in the lead halide precursor solution, exhibit desired properties, such as fewer defects. Moreover, the morphology of CH₃NH₃PbI₃ structures and surface coverage of the resulting layers are considerably different from those obtained in the absence of chloride. After gaining a rational understanding regarding the effect of chloride on the growth, morphology, and optical properties of CH₃NH₃PbI₃ structures, fabrication of devices revealing a power conversion efficiency of over 16% under standard AM 1.5 G illumination is realized. The fundamental understanding and high efficiency reported here distinguishes our results, particularly where chloride based precursors are involved.