A puzzling solar cell structure: An exercise to get insight on intermediate band solar cells

A. Martí, E. Antolín, P. García‐Linares, I. Ramiro, E. López, I. Tobías, A. Luque
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引用次数: 5

Abstract

We introduce one trivial but puzzling solar cell structure. It consists of a high bandgap pn junction (top cell) grown on a substrate of lower bandgap. Let us assume, for example, that the bandgap of the top cell is 1.85 eV (Al0.3Ga0.7As) and the bandgap of the substrate is 1.42 eV (GaAs). Is the open-circuit of the top cell limited to 1.42 V or to 1.85 V? If the answer is “1.85 V” we could then make the mind experiment in which we illuminate the cell with 1.5 eV photons (notice these photons would only be absorbed in the substrate). If we admit that these photons can generate photocurrent, then because we have also admitted that the voltage is limited to 1.85 V, it might be possible that the electron-hole pairs generated by these photons were extracted at 1.6 V for example. However, if we do so, the principles of thermodynamics could be violated because we would be extracting more energy from the photon than the energy it initially had. How can we then solve this puzzle?
一个令人困惑的太阳能电池结构:一项深入了解中间波段太阳能电池的练习
我们介绍一个微不足道但令人费解的太阳能电池结构。它由生长在低带隙衬底上的高带隙pn结(顶电池)组成。例如,我们假设顶电池的带隙为1.85 eV (Al0.3Ga0.7As),衬底的带隙为1.42 eV (GaAs)。顶部电池的开路是否限制在1.42 V或1.85 V?如果答案是“1.85 V”,那么我们可以做一个心灵实验,用1.5 eV的光子照亮电池(注意这些光子只会被衬底吸收)。如果我们承认这些光子可以产生光电流,那么因为我们也承认电压限制在1.85 V,所以有可能这些光子产生的电子-空穴对在1.6 V时被提取出来。然而,如果我们这样做,热力学原理可能会被违反,因为我们将从光子中提取比它最初拥有的能量更多的能量。那么我们如何解决这个难题呢?
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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