High minority carrier lifetime in amorphous-crystalline silicon heterostructure using triode rf PECVD

High minority carrier lifetime of more than 8 ms is achieved by depositing high quality hydrogenated amorphous silicon films on crystalline silicon using the triode plasma enhanced chemical vapor deposition (PECVD) technique. High quality surface passivation is made possible by virtue of introducing a biased grid between the two electrodes of an rf diode. In particular, by choosing an appropriate grid-substrate distance and applying a large negative DC bias on the grid, the passivation quality is substantially enhanced leading to a surface recombination velocity of 2.4 cm/s. In addition, the quality of doped amorphous silicon using the triode PECVD is also improved. An implied open circuit voltage of 710 mV is demonstrated from first silicon heterojunction solar cell devices.