Microcrystalline B-doped window layers prepared near amorphous to microcrystalline transition by HWCVD and its application in amorphous silicon solar cells

Abstract The electronic and structural properties of p-type microcrystalline silicon films prepared near the microcrystalline to amorphous (μc-amorphous) transition by hot-wire chemical vapor deposition are studied. Silane is used as a source gas while H 2 as diluent and trimethylboron (TMB) and boron trifluoride (BF 3 ) as doping gases. Increasing TMB concentration from 0.01% to 5% favors the amorphous growth whereas for BF 3 the crystalline fraction remains constant. The dark conductivity ( σ d ) of μc-Si:H p-layers remains approximately constant for TMB = 1–5% at constant crystalline fraction X c . This dark conductivity behavior is attributed to the decrease in doping efficiency with increasing TMB concentration. The best initial efficiency obtained for a 400 nm amorphous pin solar cell with optimized μc-Si:H p-layer is 7.7% ( V oc  = 874 mV, J sc  = 12.91 mA/cm 2 , FF = 68%).