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Communication Dans Un Congrès Année : 2017

Minibands modeling in strained balanced InGaAs/GaAs/GaAsP cells

Résumé

In photovoltaic, multi quantum wells (MQW) allow to tailor the optical absorption. This is particularly interesting in multijunction solar cells [1] but it also permits to improve the efficiency of a single junction solar cell [2]. This approach is efficient thanks to the strain-balanced materials which, at a well under compressive strain, associates a barrier under tensile strain. This permits to consider a large number of wells while preventing the formation of dislocations during crystal growth. On the other hand, the use of barriers is a drawback for the collection of the photo-generated carriers and more generally for the electronic transport quality in the MQW. Indeed, since transport is a succession of thermal escape, assisted tunnel escape and, at best, direct tunneling across a barrier, the average carrier velocity is low (of about 104 cm s(-1)) [3]. Finally the recombination rate is large and impacts both open-circuit voltage and short-circuit current. Furthermore, thanks to barriers some minibands can occur [4]. The wave functions of carriers in minibands are Bloch waves, meaning that propagation is efficient. Our theoretical study, based on quantum simulation (Green functions formalism) in InGaAs/GaAs/GaAsP cells, sheds light on minibands in which the average velocity of carriers is around 107 cm s-1. However, we also show that, without an adapted design, such minibands are inefficient since they connect only a few wells. We will present some improvements related to the distance between barriers and the positioning of the MQW inside the cell.
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Dates et versions

hal-01694470 , version 1 (15-05-2018)

Identifiants

Citer

Benoit Galvani, Fabienne Michelini, Marc Bescond, Masakazu Sugiyama, Jean-Francois Guillemoles, et al.. Minibands modeling in strained balanced InGaAs/GaAs/GaAsP cells. Optoelectronics and Photonic Materials and Devices Conference (SPIE OPTO), Jan 2017, San Francisco, CA, United States. ⟨10.1117/12.2252074⟩. ⟨hal-01694470⟩
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