(167a) Nanorod-like CH3NH3PbI3 for Planar Heterojunction Perovskite Solar Cell with Improved Performance

Hybrid organic-inorganic perovskite solar cell has recently attracted significant attention owing to the rapid improvement of the power conversion efficiency (PCE) as well as low cost manufacturing process. Great efforts involving high-quality perovskite film formation methodologies, compositional engineering of perovskite materials, and device architecture together with interface engineering have been made over the last six years, leading to a PCE leap from 3.8% in 2009 to the current world record of 22.1% in 2016 (NREL chart, http://www.nrel.gov/ncpv/images/efficiency_chart.jpg, Accessed 13.03.2016, 2016). The photo-to-electron conversion in perovskite solar cell involves several key steps, including light absorption by perovskite layer, charge transport in perovskite capping layer, and charge separation at n-type oxide/perovskite and perovskite/HTL interfaces. To achieve high photovoltaic performance, the morphology of perovskite is critically vital particularly for the plannar structured PSC, where the crystalline perovskite layer has to be self-standing without the support of a mesoporous scaffold.

This work reports a facile one-step HMT-assisted solution deposition method for reproducible fabrication of a high-quality nanorod-like CH₃NH₃PbI₃ thin films via controling over the CH₃NH₃PbI₃ crystallization in the presence of ammonia agent. SEM analysis review that a dense and grain-boundary-free perovskite capping layer can be prepared with orienting alignment of perovskite grains that fully cover the ammonia-modified ZnO substrate. XRD results demonstrate a high purity of CH₃NH₃PbI₃ thin film without no PbI₂ impurity. The perovskite film produces an appreciable enhancement in both photovoltaic performance and reproducibility as comparison with pristine perovskite, leading to an average PCE of 14.87±0.78%. The introduction of ammonia agent as nucleation-controlling and crosslinking agents and interface modifier provides a facile and effective approach for processing high purity and grain-boundary-free metal-halide perovskite thin film and tune the oxide/perovskite interface. The simplicity, ammonia agent-assisted and low temperature solution method can extend to construction of other perovskite-based hybrid optoelectronic devices.