Band gap profiles of intrinsic amorphous silicon germanium films and their application to amorphous silicon germanium heterojunction solar cells

•The properties of i-a-SiGe:H films improvement by the VU shape band gap profile technique.•The effect of VU shape band gap profile in a-SiGe:H heterojunction solar cells were investigated.•We characterized a-SiGe:H solar cells using the flat, V, U and VU shape band gap profiles.•The VU shape band gap profile shows a high efficiency and the photovoltaic parameters.

Intrinsic amorphous silicon germanium (i-a-SiGe:H) films with V, U and VU shape band gap profiles for amorphous silicon germanium (a-SiGe:H) heterojunction solar cells were fabricated. The band gap profiles of i-a-SiGe:H were prepared by varying the GeH4 and H2 flow rates during the deposition process. The use of i-a-SiGe:H with band gap profile in an absorber layer for a-SiGe:H heterojunction solar cells was investigated. The solar cell using a VU shape band gap profile shows a higher efficiency compared to other shapes. The highest efficiency obtained for an a-SiGe:H heterojunction solar cell using the VU shape band gap profile technique was 9.4% (Voc = 0.79 V, Jsc = 19.0 mA/cm2 and FF = 0.63).