The unique electronic features of highly mismatched alloys such as III-V GaNAs are suitable for the intermediate band solar cell (IBSC) application, in which an intermediate band (IB) acts as a stepping stone to generate additional photocarriers across the host semiconductor bandgap through sequential two-step below-bandgap photon absorption (TSPA). However, the collection of photocarriers in a realistic GaNAs IBSC is much lower and often accompanies S-shape kink features in the current–voltage (J–V) curves under illumination for which a coherent picture is lacking. Based on the solar cell characterization of GaNAs IBSC devices grown with and without barriers, with and without antimony, and with and without indium using molecular beam epitaxy, and also with the photocarrier collection analysis using equivalent circuit models, it was identified that the TSPA and the S-shape J–V of this system depend on two critical factors: (1) high carrier recombination currents (I0CI) across the GaNAs sub-gap between the conduction- and intermediate bands (EgCI) and (2) the counterdiode effect of the AlGaAs IB electron barrier. Dramatic improvements in the S-shape J–V feature of the solar cell characteristics were achieved when lattice-strain was compensated in GaInNAsSb epitaxial layers.

中文翻译：

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中带太阳能电池中光载流子的收集：实验和等效电路分析

III-V GaN 等高度失配合金的独特电子特性适用于中带太阳能电池 (IBSC) 应用，其中中带 (IB) 充当垫脚石，通过主体半导体带隙产生额外的光载流子连续两步带隙以下光子吸收（TSPA）。然而，在现实的 GaNAs IBSC 中，光载流子的收集要低得多，并且在缺乏连贯图像的光照下，电流-电压 (J-V) 曲线中通常伴随着 S 形扭结特征。基于使用分子束外延生长的有和没有阻挡层、有和没有锑、有和没有铟生长的 GaNAs IBSC 器件的太阳能电池特性，以及使用等效电路模型的光载流子收集分析，已确定该系统的 TSPA 和 S 形 J-V 取决于两个关键因素：（1）高载流子复合电流（I0CI）穿过导带和中间带（EgCI）之间的 GaNs 子间隙和(2) AlGaAs IB电子势垒的反二极管效应。当在 GaInNASSb 外延层中补偿晶格应变时，太阳能电池特性的 S 形 J-V 特征得到了显着改善。