Effect of Annealing Temperature on Film Morphology of Organic–Inorganic Hybrid Pervoskite Solid‐State Solar Cells

TLDR

Organic–inorganic hybrid perovskites are promising light‑harvesting materials for mesoscopic solid‑state solar cells, achieving record efficiencies, but their performance depends critically on film morphology shaped by deposition and post‑treatments. The study investigates how annealing temperature influences the conversion of the precursor solution into perovskite and its subsequent effect on film morphology, composition, and device performance. The perovskite film is spin‑coated from a PbCl₂/CH₃NH₃I precursor solution in dimethylformamide, then annealed at varying temperatures to induce solvent evaporation and crystallization. Sufficiently high annealing temperatures are needed to evaporate solvent and crystallize perovskite, but temperatures that are too high cause excess PbI₂ formation, degrading photovoltaic performance.

Abstract

Organic–inorganic hybrid perovskites have attracted attention as successful light harvesting materials for mesoscopic solid‐state solar cells and led to record breaking efficiencies. The photovoltaic performance of these devices is greatly dependent on the film morphology, which in turn is dependent on the deposition techniques and subsequent treatments employed. In this work the perovskite film is deposited by spin‐coating a precursor solution of PbCl 2 and CH 3 NH 3 I (1 to 3 molar ratio) in dimethylformamide. Here, the role of the temperature used in the annealing process required to convert the as deposited solution into the perovskite material is investigated. It is found that the conversion requires sufficiently high temperatures to ensure the vaporization of solvent and the crystallization of the perovskite material. However, increasing the annealing temperature too high leads to the additional formation of PbI 2 , which is detrimental to the photovoltaic performance. Furthermore, the effect of the annealing temperature on the film formation, morphology, and composition is examined and correlated with the photovoltaic performance and device working mechanisms.