Optimization of a-Si:H absorber layer grown under a low pressure regime by plasma-enhanced chemical vapor deposition: Revisiting the significance of the p/i interface for solar cells

Abstract

In this study, we revisited the significance of the p/i interface for hydrogenated amorphous silicon (a-Si:H) solar cells. Initially, intrinsic and extrinsic (p and n type) a-Si:H layers were grown in a low pressure regime (0.5–0.1Torr) using the conventional RF plasma-enhanced chemical vapor deposition process and their opto-electronic properties were optimized for the fabrication of p–i–n a-Si:H solar cells. Subsequently, we obtained new insights in terms of the activation energy and band gap at the p/i interface in these solar cells. The absorber layers deposited at pressures of 0.23Torr and 0.53Torr had the highest photosensitivity with a band absorption edge at ~700nm. Furthermore, the photosensitivity was shown to be correlated with the estimated diffusion length, which effectively defined the carrier transport within the solar cell layers. Moreover, the cell efficiency increased from 1.53% to 5.56% due to the improved p/i interface as well as the higher photosensitivity of the intrinsic/absorber layer.