Development of a Hot-Wire Chemical Vapor Deposition n-type Emitter on p-type Crystalline Si-Based Solar Cells

We have developed a p-type, crystalline Si-based solar cell using hot-wire chemical vapor deposition (HWCVD) n-type microcrystalline Si to form an n-p junction (emitter). The CVD process was rapid and a low substrate temperature was used. The p-type Czochralski (CZ) c-Si wafer has a thickness of 400 μm and has a thermally diffused Al back-field contact. Before forming the n-p junction, the front surface of the p-type c-Si was cleaned using a diluted HF solution to remove the native oxides. The n-type emitter was formed at 220 °C by depositing 50 Å a-Si:H and then a 100 Å μc-Si n-layer. The total deposition time to form the emitter was less than 1 min. The top contact of the device is a lithograph defined and isolated 1×1 cm² and 780 Å indium tin oxides (ITO) with metal fingers on top. Our best solar cell conversion efficiency is 13.3% with V_oc of 0.58 V, FF of 0.773, and J_sc of 29.86 mA cm^-2 under one-sun condition. Quantum efficiency (QE) measurement on this solar cell shows over 90% in the region between 540 and 780 nm, but poor response in the blue and deep red. We find that the ITO top contact that acts as an antireflection layer increases the QE in the middle region. To improve the device efficiency further, J_sc needs to be increased. Better emitter and light trapping will be developed in future work. The cell shows no degradation after 1000 h of standard light soaking.