Detection of Efficiency-Limiting Defects in Cadmium Telluride

Open Access
Author:
Coda, Anthony Bernard
Area of Honors:
Engineering Science
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Patrick M Lenahan, Thesis Supervisor
  • Judith Todd Copley, Honors Advisor
Keywords:
  • CdTe
  • Cadmium Telluride
  • Electron Paramagnetic Resonance
  • EPR
  • Solar
Abstract:
Cadmium telluride is one of the leading materials in thin-film solar cell technologies. CdTe solar cells have one of the highest theoretical efficiencies of all materials. However, efficiencies are currently limited due to deep-level defects acting as recombination centers. It is currently not well understood how the properties of different dopants contribute to the introduction of new defects or augmentation of existing intrinsic defects. In this study, Electron Paramagnetic Resonance (EPR) is used to characterize the defects present in undoped, p-type, and n-type CdTe. The differences in the EPR spectra for differently doped samples provides evidence that particular dopants may not be well suited for solar cell applications. Most notably, EPR signals in As-doped CdTe may have indicated a significant concentration of tellurium vacancies, which may act as efficiency-limiting recombination centers in solar cell applications due to their energy level near the center of the CdTe band gap.