Berlin 2018 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 21: Photo-voltaics II
HL 21.5: Talk
Tuesday, March 13, 2018, 15:00–15:15, EW 202
Exceeding the Shockley-Queisser limit within the detailed balance framework — •Marnik Bercx, Rolando Saniz, Bart Partoens, and Dirk Lamoen — EMAT & CMT groups, Department of Physics, University of Antwerp
The Shockley-Queisser limit is one of the most fundamental theoretical results in the field of photovoltaics. Based on the principle of detailed balance, it defines an upper limit for a single junction solar cell that uses an absorber material with a specific band gap. More recently, Yu and Zunger introduced a more refined selection metric, the Spectroscopic Limited Maximum Efficiency (SLME), which includes the absorptivity of the material in the calculation of the efficiency. We use first-principles DFT calculations based on the HSE06 functional to determine the SLME of the CuAu-like phase of a selected list of I-III-VI2 compounds, and find several materials with a calculated efficiency above the corresponding chalcopyrite material. Moreover, we find materials for which the calculated efficiency is above the Shockley-Queisser limit. Although it is possible to surpass the Shockley-Queisser limit using several mechanisms, none of these are implemented in the SLME. We show that it is possible to exceed the Shockley-Queisser limit within the detailed balance approach, related to the fact that Shockley and Queisser’s assumption of optimal absorption properties also maximizes the recombination current. We conclude that considering a finite thickness for the absorber layer allows the efficiency to exceed the Shockley-Queisser limit, and that this is more likely to occur for materials with small band gaps.