National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
Department of Physics, Colorado School of Mines , Golden, Colorado 80401, United States.
Nano Lett. 2017 Feb 8;17(2):1020-1027. doi: 10.1021/acs.nanolett.6b04423. Epub 2017 Jan 13.
We developed a monolithic CdTe-PbS tandem solar cell architecture in which both the CdTe and PbS absorber layers are solution-processed from nanocrystal inks. Due to their tunable nature, PbS quantum dots (QDs), with a controllable band gap between 0.4 and ∼1.6 eV, are a promising candidate for a bottom absorber layer in tandem photovoltaics. In the detailed balance limit, the ideal configuration of a CdTe (E = 1.5 eV)-PbS tandem structure assumes infinite thickness of the absorber layers and requires the PbS band gap to be 0.75 eV to theoretically achieve a power conversion efficiency (PCE) of 45%. However, modeling shows that by allowing the thickness of the CdTe layer to vary, a tandem with efficiency over 40% is achievable using bottom cell band gaps ranging from 0.68 and 1.16 eV. In a first step toward developing this technology, we explore CdTe-PbS tandem devices by developing a ZnTe-ZnO tunnel junction, which appropriately combines the two subcells in series. We examine the basic characteristics of the solar cells as a function of layer thickness and bottom-cell band gap and demonstrate open-circuit voltages in excess of 1.1 V with matched short circuit current density of 10 mA/cm in prototype devices.
我们开发了一种整体式 CdTe-PbS 串联太阳能电池结构，其中 CdTe 和 PbS 吸收层都是通过纳米晶油墨溶液处理而成。由于其可调谐性质，PbS 量子点 (QD) 的带隙在 0.4 到 1.6 eV 之间可调，是串联光伏中底部吸收层的有前途的候选材料。在详细平衡极限下，CdTe(E=1.5 eV)-PbS 串联结构的理想配置假设吸收层的厚度无限大，并且需要 PbS 的带隙为 0.75 eV，才能从理论上实现 45%的功率转换效率 (PCE)。然而，建模表明，通过允许 CdTe 层的厚度发生变化，可以使用底部电池带隙在 0.68 和 1.16 eV 范围内实现效率超过 40%的串联结构。为了开发这项技术，我们通过开发 ZnTe-ZnO 隧道结来探索 CdTe-PbS 串联器件，该隧道结适当地将两个子电池串联起来。我们研究了太阳能电池的基本特性作为层厚度和底部电池带隙的函数，并在原型器件中展示了超过 1.1 V 的开路电压和匹配的 10 mA/cm 的短路电流密度。
