Post‐Deposition Photonic Curing Treatment for Improved Sb 2 Se 3 Photovoltaic Performance

The open circuit voltage (V OC ) deficit remains the major barrier to achieving high‐efficiency antimony selenide (Sb 2 Se 3 ) thin‐film solar cells, arising largely from non‐radiative recombination at bulk and interfacial defects. While considerable progress has been achieved through front‐interface engineering, scalable post‐deposition strategies for optimising the critical Sb 2 Se 3 back surface remain limited. Here, photonic curing (PC) is employed as a rapid millisecond‐scale processing technique for rear‐interface engineering in Sb 2 Se 3 photovoltaics. PC enhances the preferential (211)/(221) crystallographic texture and significantly smooths the absorber surface, reducing roughness by ∼53% without measurably altering the bulk material properties. These structural and morphological modifications suppress interfacial recombination and improve charge extraction, resulting in a near‐twofold increase in average power conversion efficiency from 4.1% to 6.9%, with a champion device efficiency of 8.2%. The performance enhancement is accompanied by a 67 mV increase in V OC and a ∼13% absolute improvement in fill factor. Capacitance–voltage measurements further indicate improved junction quality through a substantial increase in built‐in potential. These findings establish PC as a scalable and high‐throughput strategy for rear‐interface optimisation in Sb 2 Se 3 solar cells and highlight the broader potential of ultrafast light‐driven processing for defect and interface engineering in emerging chalcogenide photovoltaics.