Tailoring of CsPbIBr<sub>2</sub> perovskite crystallization via phenylthiourea for stable and efficiency perovskite solar cells

Inorganic CsPbIBr<sub>2</sub> perovskite has been considered as a promising light-absorbing material for solar cells due to its high stability and suitable bandgap. Although the remarkable improvement of PSC achieved, efficiency this cell is still lower than those other analogues far below theoretical limit. This mainly serious charge recombination in as-fabricated derived from poor-quality film with large quantity defects numerous grain boundaries. Therefore, fabricating high-quality key factor further PSCs. Herein, phenylthiourea (PTU) additive introduced into precursor tailor crystallization perovskite. The C=S group PTU can coordinate PbBr<sub>2</sub> owing lone-pair electrons on S empty orbits Pb<sup>2+</sup>. strong interaction between components form PTU·Pb···Br(I)) intermediate phase upon introduction. PTU·Pb···Br(I) reduce nucleation rate modulate crystal growth because extra energy required break coordination bond phase, resulting low Such retardation conducive formation high-crystallinity smooth surface, grains, crystallization, density defect. Meanwhile, decomposition during thermal annealing makes S<sup>2-</sup> inserted interstitial lattice, which greatly enhance carbon-based PSCs normal n-i-p structure FTO/compact-TiO<sub>2</sub> layer/meso-TiO<sub>2</sub> layer/perovskite film/carbon layer are fabricated, their photovoltaic performances measured under simulated AM1.5 illumination (100 mW cm<sup>–2</sup>). based PTU-CsPbIBr<sub>2</sub> delivers power conversion 10.09%, much higher that control device. great performance be attributed largely promoted quality, enhances collection suppresses In addition, unencapsulated device preserves 82% initial after being stored ambient condition 35 days, suggesting excellent stability. work provides an effective complementary strategy effectively improving inorganic