Effect of buffer layer on minority carrier lifetime and series resistance of bifacial heterojunction silicon solar cells analyzed by impedance spectroscopy

By combining information on solar cell layer structure and electrical response analyzed by impedance spectroscopy, relevant knowledge is obtained about photogenerated carriers recombination and extraction. The inclusion of a-Si:H buffer layers on the response of bifacial heterojunction silicon solar cells prepared by hot-wire chemical vapor deposition is studied. Impedance analysis indicates that the effect of the buffer layer is twofold: (a) effective minority carrier lifetime is improved by one order of magnitude, confirmed by alternative quasi-steady-state photoconductance, and (b) whole series resistance is increased. Both effects seem to compensate each other so as to get similar efficiency and fill factor.