Promising window layer of thin film Si solar cell with p–i–n structure prepared by using SiH2Cl2

The fabrication process for a-Si:H solar cells with p–i–n structure contains a problem of damage to the SnO2 substrate particularly at higher process temperatures. We have reported that the suppression of darkening and wide optical gap (Eopt) are obtained by using SiH2Cl2 instead of SiH4 as a source gas (Mater. Res. Soc. Symp. Proc. 609 (2000), in press). In this paper, p-type a-Si:H:(Cl) was investigated. Comparable Eopt and dark conductivity (σdark) to those of conventional a-SiC:H were obtained. Solar cells using this a-Si:H:(Cl) show higher current density (Jsc) and higher collection efficiency in all wavelength regions as compared to a p-layer not using chlorine processes. The newly developed p-layer has been applied to solar cells with p–i–n structure fabricated at higher substrate temperatures (Ts). Although the a-Si:H material deposited at higher substrate temperatures has been reported as being more stable against light soaking (21st IEEE PVSC Proceeding, Florida, USA, 1990, p. 1656), the high temperature processing is difficult to apply to the a-Si:H p–i–n structure because of the significant darkening of SnO2 at higher Ts. With an a-Si:H:(Cl) buffer layer, a-Si:H solar cells can be fabricated at higher Ts (∼300°C) with reasonable cell performance. The best stabilized efficiency was 7.5% obtained at a Ts of 250°C.