Additive engineering has been a crucial strategy to improve photovoltaic properties by reducing carrier trap centers or increasing carrier diffusion lengths in the lead halide perovskite active layer. We introduced a small amount of CH₃NH₃⁺NO₃^- (methylammonium nitrate, MAN) to a pristine MAPbl₃ precursor solution as an agent for controlling the grain growth rate and healing iodine vacancies at grain boundaries of a perovskite film. With an addition of MAN, the larger grains were formed, confirmed by surface morphology images, and higher environmental  stability was evidenced by in situ impedance spectroscopy results. For the  optimized sample with an addition of 0.3 mol % MAN, high power conversion efficiency (PCE) of 20.5% (18.7% for the pristine sample) was successively demonstrated. In addition, the remnant NO3 ions were identified at the perovskite grain boundaries at room temperature and inside the unit cell at high temperature, as evidenced by results of in situ X-ray diffraction and in situ UV−visible spectroscopy measurements. Temperature dependence behaviors of the additive provide an in-depth understanding for designing and selecting additives to increase the PCE and stability of the perovskite solar cells.

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- Authors (Pusan National University): 

 · First author: Sun-Ju Kim (Department of Nano Fusion Technology), In Hwa Cho (Semiconductor Process and Equipment Contract Department)

 · Corresponding authors: Prof. Hyo Jung Kim (School of Chemical Engineering), Prof. Ji-Youn Seo (Department of Nano Fusion Technology)

- Title of original paper: Methylammonium Nitrate-Mediated Crystal Growth and Defect Passivation in Lead Halide Perovskite Solar Cells 

- https://doi.org/10.1021/acsenergylett.4c00154 

- Journal: ACS Energy Letters