Low Temperature Back-Surface-Field (BSF) Technology for Crystalline Silicon (c-Si) Thin Film Solar Cells Based on Heterojunctions between Boron-Doped P-Type Hydrogenated Amorphous Silicon and c-Si
We propose a low temperature back-surface field (BSF) technology for crystalline silicon (c-Si) thin film solar cells. The BSF structure has a heterojunction between a p-type c-Si substrate and a boron (B)-doped p-type hydrogenated amorphous silicon (a-Si:H) layer deposited on the back surface of the c-Si substrate at 200degC. The back-surface recombination velocity, Sb, of minority carriers can be reduced to less than 1000 cm/s in this structure, while the value of S b is 106 cm/s when a B-doped p-type layer is epitaxially grown on the c-Si substrate. We have clarified, from internal photoemission (IPE) and attenuated-total-reflection Fourier transform infrared (ATR-FTIR) spectroscopy measurements, that possible reasons for the observed low value of Sb are (1) the band lineup of the heterojunction (HJ) between B-doped p-type a-Si:H and c-Si and (2) the hydrogen passivation of defects in B-doped a-Si:H
Processed optimization for excellent interface passivation quality of amorphous/crystalline silicon solar cells
Abstract This study evaluates the interface passivation quality of the amorphous/crystalline heterointerface and the performance of the heterojunction with intrinsic thin layer solar cells via values of a plasma parameter characterized by the deposition pressure ( p )×electrode distance ( d ). Increasing the product of p × d leads to a lower crystalline fraction and higher hydrogen content, and enhances the c-Si surface passivation. This p × d evaluation factor is also compared with other evaluation factors, such as the silane depletion fraction and film-crystallinity. The tendencies of minority carrier lifetimes with respect to these evaluation factors were similar. Using the highest p × d value of 48, the photovoltaic parameter of the device yielded an open-circuit voltage of up to 710 mV, in turned giving an efficiency of 19.12%.
Finite Difference Modeling on the Temperature Field of Substrate in Friction Surfacing
Friction surfacing is an advanced process of great potential, especially in the field of repair and reclamation of worn and damaged components. As a kind of thermal processing technology, the temperature profile and changes of the substrate in friction surfacing are important factors to get coatings of high quality. In this paper, the temperature field of the substrate during the process is simulated by finite difference method. The results are consistent with experiments, reappearing the temperature change of the substrate during friction surfacing, allowing further study on figuration and quality of coatings.