Surface passivation of FAPbI3-rich perovskite with caesium iodide outperforms bulk incorporation

TL;DR

This study demonstrates that surface passivation of FAPbI3-rich perovskite with caesium iodide significantly improves efficiency and stability of solar cells, outperforming bulk incorporation methods.

Contribution

The paper introduces a surface passivation technique using CsI that enhances perovskite solar cell performance beyond traditional bulk doping methods.

Findings

Achieved a PCE of 24.1% with CsI passivation.

Enhanced device stability with ~90% PCE retention over 600 hours.

Provided in-depth analysis of passivation effects on material properties.

Abstract

Metal halide perovskites (MHPs) have shown an incredible rise in efficiency, reaching as high as 25.7%, which now competes with traditional photovoltaic technologies. Herein, we excluded CsX and RbX, the most commonly used cations to stabilize FAPbI3, from the bulk of perovskite thin films and applied them on the surface, as passivation agents. Extensive device optimization led to a power conversion efficiency (PCE) of 24.1% with a high fill factor (FF) of 82.2% upon passivation with CsI. We investigated in-depth the effect of CsI passivation on structural and optoelectronic properties using X-ray diffraction (XRD), angle resolved X-ray photoelectron spectroscopy (ARXPS), Kelvin Probe Force (KPFM) microscopy, time-resolved photoluminescence (TRPL), photoluminescence quantum yield (PLQY) and electroabsorption spectroscopy (TREAS). Furthermore, passivated devices exhibit enhanced operational stability, with optimized passivation with CsI leading to a retention of ~90% of initial PCE under 1 Sun illumination with maximum power point tracking for 600 h.