Orateur
Description
Cadmium telluride (CdTe) solar cells are still at the front end of the few thin-film technologies exceeding 22% of efficiency. The latter record was made possible by Se alloying in the CdTe absorber.[1] This surge in efficiency has seen the manufacturing cost reducing to such levels that now CdTe photovoltaics electricity is cheaper than popular silicon photovoltaics. CdTe has a band-gap value of ~1.5 eV close to the optimum band-gap of 1.34 eV for maximum theoretical solar cell efficiency according to the Shockley–Queisser thermodynamic limit. It has been shown that Se alloying can improve the CdTe solar cell efficiency. The first effect comes from a band-gap grading from 1.46 to 1.36 eV leading to an increase of the wavelengths absorption range. However, unavoidable native defects in the core of the semiconductor are expected to act as a non-radiative recombination center killing the energy conversion effect by capturing the charge carriers. In addition to band-gap grading, Se diffusion inside the CdTe absorber has been recently probe as a key for the passivation of some critical defects thus explaining the higher luminescence efficiency in Se alloyed solar cell. [2]
In this contribution, using density functional theory (DFT), we will provide a microscopic picture of the role of Se in the process. Our study is two folds. We first identify the mechanism responsible for the fast diffusion of Se in CdTe. Next, we analyze the role of the diffusion Se in the passivation of two harmful intrinsic defects.
References:-
[1] N. R. Paudel and Y. Yan, Applied PhysicsLetters105, 183510 (2014)
[2] T. A. M. Fiducia, B. G. Mendis, K. Li, C. R. M. Grovenor, A. H. Munshi,K. Barth, W. S. Sampath, L. D. Wright, A. Abbas, J. W. Bowers, and J. M.Walls, Nature Energy4,504–511 (2019)
| Language | English |
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