Effective surface treatment for efficient and stable inverted inorganic CsPbI2Br perovskite solar cells

Abstract

The interest in all-inorganic perovskite solar cells (PSCs) featuring a p-i-n structure is on the rise, attributed to their superior heat resistance and adaptability with tandem cell methods. However, their progress has been far from the regular structure owing to the comparatively low open circuit voltage (V_oc). This research employs phenylethylammonium iodide, incorporating various side groups, as passivators to tackle the previously mentioned problems and investigate their effects on passivation. It is found that a reduction of trap-state density in perovskite film was accomplished due to the PEAI effective passivation effect by establishing coordination with the under-coordinated Pb²⁺ ions. Furthermore, there was an enhancement in the alignment of energy levels at the CsPbI₂Br perovskite/PCBM junction, resulting in better charge extraction from the CsPbI₂Br layer to the charge transport layer. As a result, an improved champion efficiency of 14.26 % with a V_oc of 1.11 V, J_sc of 16.21 mA/cm², and FF of 79.28 % was yielded for the PEAI treatment inverted CsPbI₂Br device, compared with the 12.15 % efficiency of the control device. Superior device stability was exhibited for the optimal PEAI-treated devices without encapsulation. This research validates the significance of a side group on a surface passivation molecule to effectively passivate defects and optimize energy levels, especially for boosting V_oc.