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

Meijun Lu, Ujjwal Das, Stuart Bowden, Steven Hegedus, Robert Birkmire

Research output: Contribution to journalArticlepeer-review

62 Scopus citations

Abstract

Interdigitated back contact silicon heterojunction (IBC-SHJ) solar cells have the potential for high open circuit voltage (VOC) due to the surface passivation and heterojunction contacts, and high short circuit current density (JSC) due to all back contact design. Intrinsic amorphous silicon (a-Si:H) buffer layer at the rear surface improve the surface passivation hence VOC and JSC, 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 VOC 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.

Original languageEnglish (US)
Pages (from-to)326-338
Number of pages13
JournalProgress in Photovoltaics: Research and Applications
Volume19
Issue number3
DOIs
StatePublished - May 2011

Keywords

  • hetero-interface band alignment
  • interdigitated back contact
  • silicon heterojunction solar cell
  • surface passivation
  • two-dimensional simulation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

Fingerprint Dive into the research topics of 'Optimization of interdigitated back contact silicon heterojunction solar cells: Tailoring hetero-interface band structures while maintaining surface passivation'. Together they form a unique fingerprint.

Cite this