Improving carrier transport aided by Sb doping enables high-efficiency DMF-processed CIGSSe solar cells with sub-thickness

Abstract

Solution-processed Cu(In,Ga)(S,Se)₂ (CIGSSe) solar cells have attracted huge attention due to cost-competitive properties compared with vacuum-based solar cells. However, non-hydrazine-based solution-processed CIGSSe solar cells usually suffer from severe carrier recombination loss due to the poor absorber film without penetrated grains with numerous defects, thereby deteriorating carrier transport. In this work, Sb was directly introduced into the DMF-based CIGS precursor solution to tailor carrier transport. Sb did not enter into the CIGSSe crystal. However, Sb-related volatile phases helped to promote grain growth and eliminate the fine grain layer at the CIGSSe/Mo interface. They also spontaneously formed a single Ga gradient CIGSSe absorber layer and, thus, formed a strong built-in electronic field to facilitate carrier transport. Also, Sb doping could lower band tail states and interface/bulk defects. Ultimately, an 16.33% efficient CIGSSe solar cell was fabricated with only a 1.2 µm-thick CIGSSe absorber layer, which is the highest efficiency for a DMF solution-processed CIGSSe solar cell with sub-thickness. This work strengthens the potential validity of a non-hydrazine solution-processed CIGSSe solar cell, and also affords a pathway to fabricate a thin-film solar cell with unfavorable thickness.