A Novel Coaxial-Structured Amorphous-Silicon p-i-n Solar Cell With Al-Doped ZnO Nanowires

A novel coaxial-structured amorphous-silicon (a-Si) p-i-n solar cell with 1-μm-long low-temperature hydrothermally synthesized Al-doped-ZnO (AZO) nanowires was demonstrated for the first time. The conversion efficiency η increased from 3.92% to 4.27% when the intrinsic a-Si thickness was increased from 25 to 150 nm and then decreased to 3.66% when the intrinsic layer thickness was further increased to 250 nm. It was attributed to an excessively thick intrinsic a-Si layer that would decrease the internal electrical field and interfere with charge separation. With the optimum intrinsic a-Si thickness of 150 nm, the conversion efficiency increased from 4.27% to 4.73% when the AZO wire length was increased from 1 to 2 μm. Moreover, the proposed coaxial-structured solar cell exhibited a nearly 46% efficiency enhancement over a conventional a-Si thin-film solar cell.