Investigation of p-type nanocrystalline silicon emitters for silicon heterojunction solar cells

P-type hydrogenated nanocrystalline silicon (p-nc-Si:H) films were prepared by plasma-enhanced chemical vapor deposition (PECVD) at 200 °C, using diborane (B2H6) diluted in hydrogen to a concentration of 1% as the doping gas. The influence of hydrogen dilution, boron doping and layer thickness on the structural, optical and electronic properties of nc-Si:H films was systematically studied by transmission, Raman, small-angle X-ray diffraction (SAXD), high resolution transmission electron microscopy (HRTEM) and Fourier transform infrared (FTIR) spectroscopies. The 20 nm thick nc-Si film with dark conductivity of 0.005 S/cm and crystalline volume fraction of 43.89% was obtained. By employing p-nc-Si:H as emitter layers, SHJ solar cells were fabricated. It was found that fill factor (FF) was significantly improved with increasing the p-layer thickness from 10 to 20 nm. Moreover, the SHJ solar cell with Voc of 576 mV, Jsc of 34.49 mA/cm2, FF of 74.28%, and η of 16.63% was obtained.