Manipulating back contact enables over 8%-efficient carbon-based Sb2(S,Se)3 solar cells

The low-cost and stable carbon is known as a potential electrode candidate for high-performance Sb2(S,Se)3 solar cells. However, the poor contact and absence of electron barrier at the back contact interface between Sb2(S,Se)3 absorber and carbon electrode caused serious recombination and unsatisfactory performance of carbon-based Sb2(S,Se)3 solar cell. In this work, an ultra-thin PbS layer with various strategies was introduced to modify the back interface. Compared with the generic PbS nanoparticles-based routes, the hydrothermal-derived PbS layer is more uniformly and closely coated on the rear surface of Sb2(S,Se)3 by enjoying a unique in-situ anchoring process. As a result, a benign back contact with a well-matched interface effectively reduces the contact resistance and promotes the hole collection efficiency. Consequentially, the fill factor (FF) of the device boosts from 33.0% (control device) to 65.06% (with hydrothermal-based PbS) and also delivers a device efficiency enhancement from 3.1% to 8.0%, which is the highest FF and efficiency for the carbon-based Sb2(S,Se)3 solar cells so far. This work paves a potential route for high-performance carbon-based Sb2(S,Se)3 solar cells.