An electric-field regulated crystallization process for enhanced performance of perovskite solar cells

Abstract

Perovskite solar cells (PSCs) have received tremendous attention because of their advantages of low fabrication cost and rising power conversion efficiency (PCE). However, the poor crystalline quality of perovskite materials leads to nonradiative recombination, which hinders the fabrication of high-performance PSCs. Herein, a new method is provided to improve the crystalline quality of perovskite films by applying an external electric field (EEF) during the two-step deposition process. High-quality films were obtained by regulating ion (MA⁺ and FA⁺) migration behavior in lead iodide (PbI₂) with an ∼MV m⁻¹ electric field. The results show that the trap density can yield an ∼22.63% drop to 2.82 × 10¹⁵ cm⁻³ after the EEF-assisted process. Meanwhile, the solar cell has shown a nearly 5% improvement of PCE to 19.76% and an ∼86.7% mitigation of the hysteresis index to 3.49%, compared with the pristine one. The results can be ascribed to the ion (MA⁺ and FA⁺) migration to PbI₂ under the EEF, thereby forming a film with few defects at surfaces and between grain boundaries, which will effectively reduce the photo-generated electron–hole nonradiative recombination in PSCs. This work provides a new physical approach to fabricate high-quality perovskite materials for enhancing the performance of photovoltaic devices.