Toward cesium halide-gradient stabilized CH3NH3PbI3 perovskite solar cells

Halide-Gradient intercalation emerges as a promising strategy for enhancing the stability of perovskite solar cells (PSCs). In this study, we systematically investigate the effects of interfacial cesium halide (CsX, X = Cl, Br, I) intercalation on the morphology and crystallinity, charge transport properties, and environmental stability of CH 3 NH 3 I 3 (MAPbI 3 )-based PSCs. A gradient interlayer of CsX was vacuum deposited on both sides of perovskite films. Comprehensive characterization revealed that Br − and Cl − effectively increase crystallinity, passivate defects, and facilitate charge extraction. Among the three halides, Br − intercalated devices achieved the highest power conversion efficiency (PCE) of 18.93 %, along with minimal hysteresis and excellent reproducibility. Long-term stability tests under 30 %–40 % relative humidity and thermal aging at 85 °C revealed that devices with intercalated Br − and Cl − retained over 85 % of their initial PCE after 4000 and 640 h, respectively. These findings highlight that interfacial halide intercalation, particularly with Br − , is a viable approach to improve the operational stability of perovskite photovoltaics, with minimal efficiency compromise. • A gradient interlayer of CsX was vacuum deposited on both sides of CH 3 NH 3 PbI 3 perovskite films. • While the initial PCE can be compromised, long-term device stability cannot be compromised as it is crucial to assess the applicability of PSCs. • Devices with CsBr - and CsCl - intercalation retained over 85% of initial PCE after 4000 h (30–40% RH) and 640 h (85 °C), demonstrating excellent long-term moisture and thermal stability, respectively. • After 290 min of AM 1.5G illumination, CsI - , CsBr - , and CsCl - intercalated devices retained 89%, 92%, and 90% of initial efficiency, vs. 68% for the pristine device. • These results highlight halide ions’ role in enhancing PSC stability, paving the way for their commercialization.