Fabrication of heterojunction crystalline Si solar cells with BaSi <sub>2</sub> thin films prepared by a two-step evaporation method
Yoshihiko Nakagawa, Kazuma Takahashi, Michinobu Fujiwara, Kosuke O. Hara, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Takashi Itoh, Takashi Suemasu, Noritaka Usami
Abstract
Abstract We have fabricated p-type BaSi 2 (p-BaSi 2 )/n-type crystalline Si (n-c-Si) heterojunction solar cells using thermal evaporation. To control the defect around the heterointerface, samples were fabricated by two methods using different current profiles during evaporation. The one-step method was designed to avoid supplying Ba-rich vapor, and the two-step method was designed to intentionally introduce Ba-rich vapor at the first step. Deep-level transient spectroscopy measurements revealed that defect densities in the n-c-Si side were almost the same for both samples. Open-circuit voltage ( V oc ) was successfully improved from 319 to 463 mV by the two-step method. This may be due to the increase of carrier density in p-BaSi 2 prepared using a two-step method. As a result of optimization, the conversion efficiency of 6.23% was achieved by the heterojunction solar cells.