Textured surface ZnO:B/(hydrogenated gallium-doped ZnO) and (hydrogenated gallium-doped ZnO)/ZnO:B transparent conductive oxide layers for Si-based thin film solar cells

Abstract

Textured surface un-doped zinc oxide (ZnO) and boron-doped ZnO (ZnO:B) thin films with pyramid-like grains were directly deposited by metal organic chemical vapor deposition (MOCVD) technique and hydrogenated gallium-doped ZnO (HGZO) thin films with good electrical properties were grown by pulsed direct-current magnetron sputtering. In order to obtain high quality transparent conductive oxides (TCOs) for Si-based thin film solar cells, through combining the advantages of MOCVD–ZnO and sputter-HGZO thin films, bi-layer textured surface glass/ZnO:B/HGZO and glass/HGZO/ZnO:B TCO thin films with milky surface were fabricated and investigated in detail. The main research purposes are to explore appropriate surface morphology and improve the electrical properties of TCO layers. Compared with textured surface un-doped ZnO and ZnO:B thin films, both the bi-layer ZnO/HGZO and ZnO:B/HGZO thin films exhibit high electron mobility. The ZnO:B/HGZO thin films present modified pyramid-like surface morphology with high transparencies (T>85%) and excellent electrical properties (resistivity of ~9.28×10−4Ωcm and mobility of ~28.8cm2/Vs). Meanwhile, the HGZO/ZnO thin films exhibit large grain size (~500nm–1000nm) with preferred growth orientations along (100) and (002) crystallographic directions. Bi-layer HGZO/ZnO and HGZO/ZnO:B thin films exhibit relatively higher diffuse transmittance than that of corresponding ZnO and ZnO:B thin films.