Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 6: Photovoltaics I

HL 6.3: Talk

Monday, March 12, 2018, 10:00–10:15, EW 203

Computational investigation of quantum well superlattice solar cells — Urs Aeberhard¹ and •Jose Maria Ulloa² — ¹IEK-5 Photovoltaik, Forschungszentrum Jülich, 52425 Jülich, Germany — ²Institute for Systems based on Optoelectronics and Microtechnology (ISOM), Universidad Politécnica de Madrid, Ciudad Universitaria s/n, E-28040 Madrid, Spain

Quantum well superlattices (QWSL) are widely considered as tunable absorbers in high-efficiency multi-junction solar cells. In conventional models for the photovoltaic properties of QWSL, the latter is treated as an effective bulk medium with modified material parameters derived from a perfectly periodic structure, where transport is assumed to proceed in band-like fashion via extended superlattice Bloch states. In realistic implementations, deviations from this flat-band bulk picture are induced by the presence of built-in fields, scattering and disorder, as well as the finite number of periods.

We quantify these deviations using a comprehensive non-equilibrium quantum statistical mechanics approach to the computation of charge carrier dynamics in non-idealized QWSL. By consideration of the spectral information on density of states, scattering rates and current flow, we specifically address the transition from QWSL to multi-quantum-well behavior with increasing period thickness, type-I vs type-II band alignment, the effect of the number of SL periods, as well as the impact of electron-phonon scattering, built-in fields and disorder in the heterostructure potential. The findings are related to experimental data from type-I GaAs/GaAsNSb and type-II GaAsN/GaAsSb QWSL.