H2–CH4 mixed gas plasma treatment on LP-MOCVD ZnO:B for amorphous silicon thin film solar cells

We present an innovative dry etching method to modify the surface of in-house ZnO:B (BZO) films deposited by the LP-MOCVD technique. With the optimized hydrogen and methane mixed gas plasma post treatment process, we obtain a novel surface texture that constitutes of pyramids with enlarged feature size (>1 μm) and shrunken feature size (<0.2 μm), which can improve the light trapping capability both in short and long wavelength region. In addition, we also discuss the evolution of optical and electrical properties of BZO films with etching time. When those etched BZO films are used as front contacts in a-Si:H solar cells, the recovery of open circuit voltage and fill factor can be ascribed to the soft sharp edges of the new pyramids texture. The conversion efficiency of single a-Si:H solar cells can reach up to 6.2% for an absorber layer thickness only around 140 nm.