Optimization of interdigitated back contact silicon heterojunction solar cells: tailoring hetero-interface band structures while maintaining surface passivation

被引:72
作者
Lu, Meijun [1 ]
Das, Ujjwal [1 ]
Bowden, Stuart [1 ]
Hegedus, Steven [1 ]
Birkmire, Robert [1 ]
机构
[1] Univ Delaware, Inst Energy Convers, Newark, DE 19716 USA
来源
PROGRESS IN PHOTOVOLTAICS | 2011年 / 19卷 / 03期
关键词
silicon heterojunction solar cell; interdigitated back contact; hetero-interface band alignment; surface passivation; two-dimensional simulation; HYDROGENATED AMORPHOUS-SILICON; SI; EFFICIENCY; SPECTROSCOPY; INTERFACE; OFFSETS;
D O I
10.1002/pip.1032
中图分类号
TE [石油、天然气工业]; TK [能源与动力工程];
学科分类号
0807 ; 0820 ;
摘要
Interdigitated back contact silicon heterojunction (IBC-SHJ) solar cells have the potential for high open circuit voltage (V-OC) due to the surface passivation and heterojunction contacts, and high short circuit current density (J(SC)) due to all back contact design. Intrinsic amorphous silicon (a-Si: H) buffer layer at the rear surface improve the surface passivation hence V-OC and J(SC), but degrade fill factor (FF) from an "S'' shape J-V curve. Two-dimensional (2D) simulation using "Sentaurus device'' demonstrates that the low FF is related to the valence band offset (energy barrier) at the hetero-interface. Three approaches to the buffer layer are suggested to improve the FF: (1) reduced thickness, (2) increased conductivity, and/or (3) reduced band gap. Experimental IBC-SHJ solar cells with reduced buffer thickness (<5 nm) and increased conductivity with low boron doping significantly improves FF, consistent with simulation. However, this has only marginal effect on efficiency since J(SC) and V-OC also decrease due to poor surface passivation. A narrow band gap a-Si:H buffer layer improves cell efficiency to 13.5% with unoptimized passivation quality. These results demonstrate that tailoring the hetero-interface band structure is critical for achieving high FF. Simulations predicts that efficiences >23% are possible on planar devices with optimized pitch dimensions and achievable surface passivation, and 26% with light trapping. This work provides criterion to design IBC-SHJ solar cell structures and optimize cell performance. Copyright (C) 2010 John Wiley & Sons, Ltd.
引用
收藏
页码:326 / 338
页数:13
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