Compositional Engineering of Single-Crystal Perovskite for Highly Efficient Photovoltaics

Organic-inorganic lead halide perovskite materials have received great attention for promising opto-electric devices. To achieve high performance solar cells, defect control in perovskite materials is very crucial. Single-crystal perovskite-based solar cell exhibits excellent carrier diffusion length and light absorption due to significantly reduced bulk defects. In here, we discuss compositional engineering of single-crystal perovskite films for highly efficient perovskite solar cells. Single crystal perovskite films were grown by space-limited inverse temperature crystallization (ITC) method. Due to different solubility of perovskite precursor solute, γ-butyrolactone (GBL) and <i>N</i>,<i>N</i>-dimethylformamide (DMF) solvent ratio should be precisely controlled for compositional engineering. We investigated the effect of mixture solvent on growing single crystal perovskites. X-ray diffraction patterns confirmed that composition of perovskite can be controlled by the composition of perovskite precursor solution. We successfully synthesize wide-bandgap perovskite films and confirmed using UV-vis-NIR analysis. Single-crystal films over 4 mm were grown on ITO/PTAA substrates, and we fabricated single-crystal perovskite-based solar cells. The device shows high external quantum efficiency due to the micrometer-size film thickness. The best performing devices exhibited power conversion efficiency of over 20%.