Injection dependent minority carrier lifetime and defect configuration in thin film CdTe solar cells

Zimeng Cheng, Alan E. Delahoy, Ken K. Chin

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

Abstract

Although in CdS/CdTe thin film solar cells, experiments showed that the minority carrier lifetime depends on excess carrier concentration, it is not known that under steady state how the lifetime is affected by the defects. High defect concentration in CdS/CdTe solar cells violates the assumption needed to simplify of the Shockley Read Hall (SRH) recombination equation. Also, with high defect concentrations and thus short carrier lifetime, the excess carrier concentration under illumination can be equivalent to or even lower than the defect concentrations. By simplifying SRH equation considering high defect concentration, it is found that in neutral region, the lifetime is excess carrier dependent. By simultaneously solving the equations of charge neutrality, charge conservation and SRH recombination in the neutral region, the minority carrier lifetime as a function of generation rate can be calculated. The measured minority carrier diffusion length in a CdS/CdTe solar cell, as determined from the steady-state photo-generated carrier collection efficiency, shows the predicted transition of minority carrier lifetime versus optical injection level. A numerical fitting of the indirectly-measured minority carrier lifetime by assuming the minority carrier mobility gives a non-intuitive picture of the p-n junction with a low free hole concentration but a narrow depletion region width.

Original languageEnglish (US)
Title of host publication2014 IEEE 40th Photovoltaic Specialist Conference, PVSC 2014
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages1596-1600
Number of pages5
ISBN (Electronic)9781479943982
DOIs
StatePublished - Oct 15 2014
Event40th IEEE Photovoltaic Specialist Conference, PVSC 2014 - Denver, United States
Duration: Jun 8 2014Jun 13 2014

Publication series

Name2014 IEEE 40th Photovoltaic Specialist Conference, PVSC 2014

Other

Other40th IEEE Photovoltaic Specialist Conference, PVSC 2014
CountryUnited States
CityDenver
Period6/8/146/13/14

All Science Journal Classification (ASJC) codes

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

Keywords

  • CdTe solar cell
  • Minority carrier diffusion length
  • Minority carrier lifetime
  • Recombination

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  • Cite this

    Cheng, Z., Delahoy, A. E., & Chin, K. K. (2014). Injection dependent minority carrier lifetime and defect configuration in thin film CdTe solar cells. In 2014 IEEE 40th Photovoltaic Specialist Conference, PVSC 2014 (pp. 1596-1600). [6925225] (2014 IEEE 40th Photovoltaic Specialist Conference, PVSC 2014). Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/PVSC.2014.6925225