Solution-processed SnO ₂ interfacial layer for highly efficient Sb ₂ Se ₃ thin film solar cells

Antimony selenide (Sb ₂ Se ₃ ) thin film solar cells have gained worldwide intense research owing to their suitable bandgap, high absorption coefficient, benign grain boundaries, earth-abundant element constituents and low fabrication cost. It is extremely important to investigate the interface passivation and minimize the carrier recombination to realize high-efficiency Sb ₂ Se ₃ solar cells. Very little is known, however, about the carrier recombination mechanisms at the interfaces of Sb ₂ Se ₃ solar cells. Herein, we show that a novel solution-processed SnO ₂ layer (∼12 nm) incorporated into Sb ₂ Se ₃ thin film solar cells results in high power conversion efficiency of 7.5%, namely, an improvement of 39% relative to that of the solar cell without SnO ₂ interfacial layer. Furthermore, the open-circuit voltage (V _oc ) is the highest ever reported for Sb ₂ Se ₃ solar cells. These improvements benefit from the better preferred [221] orientation, less bulk and interfacial defects in the Sb ₂ Se ₃ absorbers, and relatively ideal heterointerfaces due to the SnO ₂ passivation. This work opens up new routes for the critical importance of interfacial control in Sb ₂ Se ₃ solar cells, which could be extended to other emerging low-dimensional thin film solar cells.