Solar cells with thin Cu(In1-xGax)Se2 absorbers: Optical analysis and quantum efficiency simulations

Abdel Rahman Ibdah, Puruswottam Aryal, Puja Pradhan, Grace Rajan, Jian Li, Angus A. Rockett, Sylvain Marsillac, Robert W. Collins

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


We present in-depth quantum efficiency analyses of of Cu(In,Ga)Se2 (CIGS) solar cells. Ex-situ spectroscopic ellipsometry (SE) analysis is applied to partially and fully completed solar cells with standard thickness and thin CIGS absorbers. Optical properties and multilayer structural data are deduced and used to predict the maximum obtainable quantum efficiency spectra and short-circuit current densities (Jsc). We validate optical model development and the resulting quantum efficiency (QE) simulations with experimental results for CIGS solar cells incorporating standard 2.2 μm thick absorbers. We find that both the bulk CIGS layer and the CdS-CIGS interface layer serve as active layer components and together contribute 100% of the photo-generated current. Thus, essentially all photo-generated carriers are collected from these layers. Solar cells with thin absorbers were also fabricated and efficiencies of 13.2% at 0.73 μm CIGS thickness, 10.1% at 0.50 μm and 8.0% at 0.36 μm were obtained. Although Jsc is expected to decrease with decreasing absorber thickness due to reduced optical collection, modeling results suggest that electronic losses are also occurring upon thinning the absorber, ranging from ∼ 1.3 to 1.9 mA/cm2 for cells with CIGS thicknesses from 0.73 to 0.36 μm, respectively.

Original languageEnglish (US)
Title of host publication2014 IEEE 40th Photovoltaic Specialist Conference, PVSC 2014
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages6
ISBN (Electronic)9781479943982
StatePublished - Oct 15 2014
Event40th IEEE Photovoltaic Specialist Conference, PVSC 2014 - Denver, United States
Duration: Jun 8 2014Jun 13 2014


Other40th IEEE Photovoltaic Specialist Conference, PVSC 2014
Country/TerritoryUnited States


  • CIGS
  • ellipsometry
  • optical films
  • photovoltaic cells

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Electronic, Optical and Magnetic Materials


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