Structure optimization for a high efficiency CIGS solar cell

S. H. Song, K. Nagaich, E. S. Aydil, R. Feist, R. Haley, S. A. Campbell

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

This paper uses numerical simulation to study the effects of Ga concentration profile on the performance of CuIn1-xGa xSe2 (CIGS) solar cell, including the effects of acceptor type Cu antisite defects whose concentration depends on Ga composition. These defects are the dominant deep traps in the CIGS material system. The concentration and spatial distribution of these traps affect the solar cell performance. The trap density model used in this work follows experimental reports in the literature. The trap concentration is 4.3×1015 cm-3 for CIS (x=0) and decreases to 1.2×1014 cm -3 when the Ga mole fraction, x, reaches 0.24. The trap concentration increases exponentially above x=0.30. Applying this model to solar cells with uniform composition absorber layer predicts that the power conversion efficiency reaches a maximum value of 14.6%, at x=0.24 and decreases with increasing Ga content above x=0.30, in good agreement with experimental results. When this model is used to simulate a solar cell where the Ga composition in the absorber layer is graded, the electric field produced by compositional grading improves the efficiency because of the reduced recombination rate. However compositions where x is higher than 0.45 lead to a drop in performance due to the high trap density and shorter lifetime. Both grading from the CdS/CIGS interface (forward grading), and back grading where the Ga concentration increases from the junction into the CIGS film were studied. In forward grading, the maximum efficiency is achieved when the Ga concentration is graded such that x decreases from 0.35 at the surface to 0.24 at 0.4 μm into the CIGS film. In back grading, the maximum efficiency is achieved when x increases from 0.45 at the surface to 0.5 at 0.4 μm into the CIGS film.

Original languageEnglish (US)
Title of host publicationProgram - 35th IEEE Photovoltaic Specialists Conference, PVSC 2010
Pages2488-2492
Number of pages5
DOIs
StatePublished - Dec 20 2010
Event35th IEEE Photovoltaic Specialists Conference, PVSC 2010 - Honolulu, HI, United States
Duration: Jun 20 2010Jun 25 2010

Publication series

NameConference Record of the IEEE Photovoltaic Specialists Conference
ISSN (Print)0160-8371

Other

Other35th IEEE Photovoltaic Specialists Conference, PVSC 2010
CountryUnited States
CityHonolulu, HI
Period6/20/106/25/10

    Fingerprint

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Industrial and Manufacturing Engineering
  • Electrical and Electronic Engineering

Cite this

Song, S. H., Nagaich, K., Aydil, E. S., Feist, R., Haley, R., & Campbell, S. A. (2010). Structure optimization for a high efficiency CIGS solar cell. In Program - 35th IEEE Photovoltaic Specialists Conference, PVSC 2010 (pp. 2488-2492). [5614724] (Conference Record of the IEEE Photovoltaic Specialists Conference). https://doi.org/10.1109/PVSC.2010.5614724