Experimental and simulated analysis of front versus all-back-contact silicon heterojunction solar cells: effect of interface and doped a-Si:H layer defects

Abstract

Front silicon heterojunction and interdigitated all-back-contact silicon heterojunction (IBC-SHJ) solar cells have the potential for high efficiency and low cost because of their good surface passivation, heterojunction contacts, and low temperature fabrication processes. The performance of both heterojunction device structures depends on the interface between the crystalline silicon (c-Si) and intrinsic amorphous silicon [(i)a-Si:H] layer, and the defects in doped a-Si:H emitter or base contact layers. In this paper, effective minority carrier lifetimes of c-Si using symmetric passivation structures were measured and analyzed using an extended Shockley–Read–Hall formalism to determine the input interface parameters needed for a successful 2D simulation of fabricated baseline solar cells. Subsequently, the performance of front silicon heterojunction and IBC-SHJ devices was simulated to determine the influence of defects at the (i)a-Si:H/c-Si interface and in the doped a-Si:H layers. For the baseline device parameters, the difference between the two device configurations is caused by the emitter/base contact gap recombination and the back surface geometry of IBC-SHJ solar cell. This work provides a guide to the optimization of both types of SHJ device performance, predicting an IBC-SHJ solar cell efficiency of 25% for realistic material parameters. Copyright © 2013 John Wiley & Sons, Ltd.