Light management in hydrogenated amorphous silicon germanium solar cells

•A maximum long-wavelength absorption can be achieved with proper feature sizes.•Small inclination angles enhance the absorption without affecting the Voc and FF.•An initial efficiency of 10.10% for PIN type a-SiGe:H solar cell is achieved.

A finite difference time-domain (FDTD) simulation and experimental investigation of the enhanced light absorption in superstrate (PIN) type amorphous silicon germanium solar cells (a-SiGe:H) deposited on wet-etched Aluminum-doped zinc oxide (ZnO:Al) substrates are presented. Depending on the etching times, optimal vertical and lateral surface feature sizes, which balance the light scattering intensity and the light scattering angle, exist for a-SiGe:H solar cells. The surface morphology analysis, FDTD simulation, and experimental results concurrently show the maximum absorption of the long wavelength region will be achieved when the randomly textured surface with proper vertical and lateral surface feature sizes is applied in the solar cells. Due to the small inclination angle of 5°–20° on the wet-etched ZnO:Al surfaces, the light absorption is enhanced without producing a negative effect on the open circuit voltage (Voc) and fill factor (FF) of the a-SiGe:H solar cell, unlike the negative effects seen in hydrogenated microcrystalline silicon solar cell (μc-Si:H) on low-pressure chemical vapor deposition (LPCVD) ZnO substrates. An initial efficiency of 10.10% for PIN type a-SiGe:H single junction solar cell was achieved by adopting the optimized surface morphology.