Surface passivation properties of boron and phosphor-doped a-Si:H films with multi-step deposition for si heterojunction solar cells

Heterojunction, such as the crystalline silicon(c-Si)/hydrogenated amorphous silicon (a-Si:H), forms a high quality passivation properties and developed for a very low recombination contact for photovoltaic devices. As low as doppant concentration (like un-doped or intrinsic), the defect density is decreased and its passivation properties is enhanced, however, in case of emitter or BSF, the low doppant concentration can cause higher contact resistance with TCO or metal electrode simultaneously, so the doping concentration limited by this reason. In this work, we studied the method avoiding doppant concentration limitation in p and n type a-Si:H films with multi layer deposition. The doped p and n type a-Si:H films were divided as two layers, passivation and contacting, through in-situ multistep deposition with different doppant flow rate. The passivation properties of multistep deposited p type a-Si:H films revealed that there were no degradation of lifetime(τeff) and implied Voc as increasing doppant concentration, differ from n type case, and showed enhanced open circuit voltage and quantum efficiency at short wavelength.