Weiliang Wu

Silicon based solar cells using a multilayer oxide as emitter

In this work, n-type silicon based solar cells with WO3/Ag/WO3 multilayer films as emitter (WAW/n-Si solar cells) were presented via simple physical vapor deposition (PVD). Microstructure and composition of WAW/n-Si solar cells were studied by TEM and XPS, respectively. Furthermore, the dependence of the solar cells performances on each WO3 layer thickness was investigated. The results indicated that the bottom WO3 layer mainly induced band bending and facilitated charge-carriers separation, while the top WO3 layer degraded open-circuit voltage but actually improved optical absorption of the solar cells. The WAW/n-Si solar cells, with optimized bottom and top WO3 layer thicknesses, exhibited 5.21% efficiency on polished wafer with area of 4 cm2 under AM 1.5 condition (25 °C and 100 mW/cm2). Compared with WO3 single-layer film, WAW multilayer films demonstrated better surface passivation quality but more optical loss, while the optical loss could be effectively reduced by implementing light-trapping struct...

Chromium Trioxide Hole-Selective Heterocontacts for Silicon Solar Cells

A high recombination rate and high thermal budget for aluminum (Al) back surface field are found on the industrial p-type silicon solar cells. Direct metallization on lightly doped p-type silicon, however, exhibits a large Schottky barrier for the hole because of Fermi-level pinning effect. In this contribution, low temperature deposited, dopant-free chromium trioxide (CrOx, x\lt3) with high stability and high performance, is first applied in a p-type silicon solar cell as a hole-selective contact at the rear surface. Implementing the advanced holeselective contacts with CrOx/Ag/CrOx on the p-type silicon solar cell results in a power conversion efficiency of 20.3%.

22% efficient dopant-free interdigitated back contact silicon solar cells

In this study, we present dopant-free back contact heterojunction silicon solar cells employing MoOx and MgFx based stacks as hole-and electron-selective contacts deposited using a thermal evaporation process at low temperature. Only two masking steps and one alignment are required in this simple process flow. We investigate the effect of varying the MgFx film thickness as the electron contact layer on the rear side on IBC Si solar cells and define an optimal thickness 1.5 nm of MgFx for high VOC and FF. We compare different electron-selective contact materials including Mg-based and fluoride materials and discuss the suitable combinations. We fabricate dopant-free back contact solar cells by applying a stack of 1.5 nm MgF2/70 nm Al/800 nm Ag films on intrinsic a-Si:H, maintaining excellent passivation and show efficient carrier extraction. A 4.5-cm2 dopant-free back contact solar cells fabricated with these layers enables high VOC up to 709 mV and FF up to 75.6% still limited by series resistance due to too thin metal layers, a pseudo FF of 84.2% is yet measured. The cell exhibits very low front reflection and has outstanding collection efficiency, the IQE reach 98.2% - 99% ranging from 600 to 900-nm due to low recombination of MoOx and MgFx contacts results in a high JSC of 41.5 mA/cm2.In this study, we present dopant-free back contact heterojunction silicon solar cells employing MoOx and MgFx based stacks as hole-and electron-selective contacts deposited using a thermal evaporation process at low temperature. Only two masking steps and one alignment are required in this simple process flow. We investigate the effect of varying the MgFx film thickness as the electron contact layer on the rear side on IBC Si solar cells and define an optimal thickness 1.5 nm of MgFx for high VOC and FF. We compare different electron-selective contact materials including Mg-based and fluoride materials and discuss the suitable combinations. We fabricate dopant-free back contact solar cells by applying a stack of 1.5 nm MgF2/70 nm Al/800 nm Ag films on intrinsic a-Si:H, maintaining excellent passivation and show efficient carrier extraction. A 4.5-cm2 dopant-free back contact solar cells fabricated with these layers enables high VOC up to 709 mV and FF up to 75.6% still limited by series resistance due to ...