Fundamental Limiting Efficiency and Intrinsic Loss Components of Quantum-Wire Intermediate-Band Solar Cells

Abstract

Quantum-wire intermediate-band solar cells (QW IBSCs) are good candidates for breaking the Shockley-Queisser limit; however, there are a few studies of them. In this paper, we derive the fundamental limiting efficiency (FLE), the theoretical upper limit of the power-conversion efficiency, for QW IBSCs by calculation of the intrinsic loss. To achieve this, based on a photon-electron detailed-balance principle, the intrinsic loss components (ILCs) are modeled in the QW IBSCs by our considering photon absorption and emission for two transverse directions of confined carriers and for a longitudinal direction of free carriers in the QWs. Furthermore, the ILCs and FLE are investigated in an experimental reported structure of an ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}/\mathrm{Ga}\mathrm{As}$ QW IBSC. For this purpose, the two-dimensional Schr\"odinger equation and the Bloch approximation are used to obtain the placement and width of the intermediate band, respectively. Besides, the effect of changing the indium content, the diagonal length, and the period of QWs, which is a way to engineer the placement and width of the intermediate band and consequently the ILCs and FLE, on the FLE of ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}/\mathrm{Ga}\mathrm{As}$ QW IBSCs is examined.