Thermal Control of PbI₂ Film Growth for Two-Step Planar Perovskite Solar Cells

Abstract

We used a two-step process to fabricate planar perovskite solar cells (PSCs) in which CH3NH3I (MAI) molecules intercalated into a PbI2 film. The crystal growth of PbI2 is particularly important to achieve perovskite films with high PSC performance. Herein, we attempted to control the crystal growth of PbI2 films through a simple spin-coating method at annealing temperatures of 70, 150, 250, and 350 °C and times of 1, 5, 10, and 30 min. We investigate the effects of the high-crystallite host PbI2 film on the crystallinity, film quality, and absorption of the resulting MAPbI3 perovskite film as well as the resulting performance of the planar PSCs. Under the optimal annealing conditions, a highly crystalline PbI2 film was reproducibly achieved at 250 °C for 30 min. Precise intercalation of MAI molecules into the PbI2 film contributed to a smooth perovskite film and good PSC performance. This work develops a fundamental understanding of the thermally induced controlled crystal growth of the parent PbI2 film, which influenced the bridging and intercalation with MAI, resulting in a high-quality perovskite film. This study will guide further development based on two-step processes of perovskite films that have optimal crystallinities and morphologies that contribute to high PSC performance.

Single‐step post‐production treatment of lead acetate precursor‐based perovskite using alkylamine salts for reduced grain‐boundary related film defects

“…A pre-annealed host film is used for the majority of post-treatments using organic amine salts and for the twostep deposition procedures resulting in mixed perovskite films. [21][22] And, so far, to our best information, there is no report about post-treatment performed on wet perovskite host film with a suitable time gap before the post-treatment is carried out.…”

Low-Temperature Processed TiOx Electron Transport Layer for Efficient Planar Perovskite Solar Cells

“…The high stability and efficiency of PSCs with low-cost processing can enable the realization of economically competitive solar power. In general, there are two leading device configurations for PSCs: planar heterojunction (PHJ) and mesoporous scaffold-based devices [ 11 , 12 , 13 ]. Thin ETLs serve a key function of extracting electrons from the perovskite layer, and blocking recombination between electrons in the fluorine-doped tin oxide (FTO) and holes in the perovskite layer.…”

Photonic Processing of MAPbI3 Films by Flash Annealing and Rapid Growth for High‐Performance Perovskite Solar Cells

“…The widely extended degradation causes a decrease of absorbance with a clear slope at around 500 nm, possibly related to the PbI 2 precursor, [ 73 ] while on the other side, the 48 °C s −1 device still retains its portrait. The last two images, at 75 and 100 h, reveal a surface mostly degraded with negligible current and an absorbance that reflects only the presence of PbI 2 [ 74,75 ] due to perovskite photodecomposition.…”