Low defect interface study of intrinsic layer for c-Si surface passivation in a-Si:H/c-Si heterojunction solar cells

Abstract

High quality hydrogenated intrinsic amorphous silicon [a-Si: H(i)]layer with adequate hydrogen content and lesser void fraction is the key to obtaining good surface passivated crystalline silicon (c-Si), with high open-circuit voltage (V-oc), which will ultimately make the heterojunction with intrinsic thin layer (HIT) solar cell highly efficient. In this study, we performed good surface passivation of a HIT solar cell by depositing a-Si: H(i) layers at different working pressures from 26.7 to 107 Pa by using very high frequency of 60 MHz plasma-enhanced chemical vapor deposition. Based on spectroscopic ellipsometry and gas depletion analysis, we discuss the influence of the working pressure on the deposition mechanism, interface passivation and ultimately cell efficiency. Highest minority lifetime of about 4 ms was achieved at the highest working pressure of 107 Pa. The decrease in working pressure results in less denser and/or incorporation of epitaxy layer inside the a-Si:H(i) films, and leads to decrease in c-Si surface passivation. The performance of heterojunction solar cell device was improved with the increase of working pressure and the best photo voltage parameters of the device were found to be V-oc of 647 mV, short-circuit current density of 32.28 mA/cm(2) and efficiency of 15.57% at working pressure of 107 Pa. (C) 2012 Elsevier B.V. All rights reserved.