Performance of heterojunction solar cells with different intrinsic a-Si:H thin layers deposited by RF- and VHF- PECVD

摘要

The effect of plasma excitation frequency on the performance of intrinsic hydrogenated amorphous silicon (a-Si:H) films and heterojunction solar cells by radio-frequency (RF, 13.56 MH_z) and very-high-frequency (VHF, 40 MH_z) plasma-enhanced chemical vapor deposition (PECVD) have been investigated. The thickness and microstructure of intrinsic a-Si:H films were measured by spectroscopic ellipsometry and Fourier transform infrared spectroscopy (FTIR). The a-Si:H/c-Si interface passivation quality were determined by minority carrier lifetime and transmission electron microscopy (TEM). The current-voltage (I-V) performance of the HJT solar cells were also evaluated. The results reveal that a-Si:H films developed by RF-PECVD with a large area of parallel-plate reactors (> 1 m~2) exhibit better thickness uniformity, lower microstructure factor, and higher minority carrier lifetimes. Hence HJT solar cells have achieved efficiency of 24.9%, compared with cell efficiency of 24.6% with intrinsic a-Si:H films developed by VHF-PECVD.