Understanding the copassivation effect of Cl and Se for CdTe grain boundaries
journal contributionposted on 2021-08-06, 08:22 authored by Akash Shah, Anthony P Nicholson, Thomas Fiducia, Ali AbbasAli Abbas, Ramesh Pandey, Junliang Liu, Chris Grovenor, Michael WallsMichael Walls, Walajabad S Sampath, Amit H Munshi
Chlorine passivation treatment of cadmium telluride (CdTe) solar cells improves device performance by assisting electron−hole carrier separation at CdTe grain boundaries. Further improvement in device efficiency is observed after alloying the CdTe absorber layer with selenium. High-resolution secondary ion mass spectroscopy (NanoSIMS) imaging has been used to determine the distribution of selenium and chlorine at the CdTe grain boundaries in a selenium-graded CdTe device. Atomistic modeling based on density functional theory (DFT-1/2) further reveals that the presence of selenium and chlorine at an exemplar (110)/(100) CdTe grain boundary passivates critical acceptor defects and leads to n-type inversion at the grain boundary. The defect state analysis provides an explanation for the band-bending effects observed in the energy band alignment results, thereby elucidating mechanisms for high efficiencies observed in Se-alloyed and Cl-passivated CdTe solar cells.
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- Mechanical, Electrical and Manufacturing Engineering
- Centre for Renewable Energy Systems Technology (CREST)