Role of a-Si:H buffer layer at the p/i interface and band gap profiling of the absorption layer on enhancing cell parameters in hydrogenated amorphous silicon germanium solar cells

Abstract

Separate influences of a hydrogenated amorphous silicon (a-Si:H) buffer layer at the p/i interface and staircase band gap profiling of entire absorption layer on cell parameters, such as open-circuit voltage (Voc), short-circuit current density (Jsc) and fill factor (FF), of hydrogenated amorphous silicon germanium (a-SiGe:H) thin film solar cells are discussed. An added thin a-Si:H buffer layer at the p/i interface can mainly improve Voc and Jsc while the staircase band gap profiling can enhance FF. Consequently, a combination of the buffer layer and band gap profiling can lead to significantly enhance Voc, Jsc and especially FF. A significant performance-improvement of the a-SiGe:H solar cell from 8.3% up to 9.8% was recorded by this combination. Role of the buffer layer and band gap profiling process was examined by empirical results and simulations.