Kinetic‐Controlled Crystallization of α‐FAPbI3 Inducing Preferred Crystallographic Orientation Enhances Photovoltaic Performance

• Published in: Advanced science 2023-05, Vol.10 (14), p.e2300798-n/a
• Main Authors: Shin, Sooeun, Seo, Seongrok, Jeong, Seonghwa, Sharbirin, Anir S., Kim, Jeongyong, Ahn, Hyungju, Park, Nam‐Gyu, Shin, Hyunjung
• Format: Article
• Language: English
• Subjects: Additives; Chloride; Crystallization; crystallization kinetic; Engineering; formamidinium lead triiodide; Grain growth; Grain size; Kinetics; methylammonium chloride additive; Microscopy; Microstructure; perovskite solar cell; Phase transitions; photovoltaic performance; Physical properties; preferred orientation; Solvents; Thin films
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.202300798

Crystallization kinetic controls the crystallographic orientation, inducing anisotropic properties of the materials. As a result, preferential orientation with advanced optoelectronic properties can enhance the photovoltaic devices' performance. Although incorporation of additives is one of the most studied methods to stabilize the photoactive α‐phase of formamidinium lead tri‐iodide (α‐FAPbI3), no studies focus on how the additives affect the crystallization kinetics. Along with the role of methylammonium chloride (MACl) as a “stabilizer” in the formation of α‐FAPbI3, herein, the additional role as a “controller” in the crystallization kinetics is pointed out. With microscopic observations, for example, electron backscatter diffraction and selected area electron diffraction, it is examined that higher concentration of MACl induces slower crystallization kinetics, resulting in larger grain size and [100] preferred orientation. Optoelectronic properties of [100] preferentially oriented grains with less non‐radiative recombination, a longer lifetime of charge carriers, and lower photocurrent deviations in between each grain induce higher short‐circuit current density (Jsc) and fill factor. Resulting MACl40 mol% attains the highest power conversion efficiency (PCE) of 24.1%. The results provide observations of a direct correlation between the crystallographic orientation and device performance as it highlights the importance of crystallization kinetics resulting in desirable microstructures for device engineering. Incorporating methylammonium chloride (MACl) as an additive not only “stabilizes” the formation of formamidinium lead tri‐iodide (α‐FAPbI3), but also “controls” the crystallization kinetics. As higher concentration of MACl induces slower crystallization, it results in larger grain size and [100] preferred orientation. With improved optoelectronic properties of [100] preferentially oriented grains, the highest power conversion efficiency of 24.1% is attained.