Effect of CH₃NH₃PbI₃thickness on device efficiency in planar heterojunction perovskite solar cells

TLDR

Recent advances in CH₃NH₃PbI₃ perovskite solar cells have achieved power‑conversion efficiencies above 15 %, and planar heterojunction architectures are now preferred over mesoporous TiO₂ supports. The study aims to elucidate how cell architecture and design parameters, such as perovskite thickness and morphology, influence device performance. The authors fabricated planar heterojunction perovskite solar cells comprising a ZnO nanoparticle electron‑transport layer, a CH₃NH₃PbI₃ light‑absorbing layer, and a poly(3‑hexylthiophene) hole‑transport layer. Vapor‑phase deposition of the PbI₂ precursor allows precise control of CH₃NH₃PbI₃ thickness and morphology, yielding planar heterojunction devices with efficiencies up to 11.3 % and demonstrating that optimal performance requires a balance between light absorption and carrier transport, as excessively thick films reduce efficiency.

Abstract

Recent advances in the development of perovskite solar cells based on CH3NH3PbI3 have produced devices with power conversion efficiencies of >15%. While initial work in this area assumed that the perovskite-based cells required a mesoporous TiO2 support, many recent reports have instead focused on the development of planar heterojunction structures. A better understanding of how both cell architecture and various design parameters (e.g., perovskite thickness and morphology) affect cell performance is needed. Here, we report the fabrication of perovskite solar cells based on a ZnO nanoparticle electron transport layer, CH3NH3PbI3 light absorber, and poly(3-hexylthiophene) (P3HT) hole transport layer. We show that vapor-phase deposition of the PbI2 precursor film produces devices with performances equivalent to those prepared using entirely solution-based techniques, but with very precise control over the thickness and morphology of the CH3NH3PbI3 layer. Optimization of the layer thickness yielded devices with efficiencies of up to 11.3%. The results further demonstrate that a delicate balance between light absorption and carrier transport is required in these planar heterojunction devices, with the thickest perovskite films producing only very low power conversion efficiencies.