The hotness of the sun and the coldness of the outer space are inexhaustible thermodynamic resources for human beings. From a thermodynamic point of view, any energy conversion systems that receive energy from the sun and/or dissipate energy to the universe are heat engines with photons as the "working fluid" and can be analyzed using the concept of entropy. While entropy analysis provides a particularly convenient way to understand the efficiency limits, it is typically taught in the context of thermodynamic cycles among quasi-equilibrium states and its generalization to solar energy conversion systems running in a continuous and non-equilibrium fashion is not straightforward. In this educational article, we present a few examples to illustrate how the concept of photon entropy, combined with the radiative transfer equation, can be used to analyze the local entropy generation processes and the efficiency limits of different solar energy conversion systems. We provide explicit calculations for the local and total entropy generation rates for simple emitters and absorbers, as well as photovoltaic cells, which can be readily reproduced by students. We further discuss the connection between the entropy generation and the device efficiency, particularly the exact spectral matching condition that is shared by infinite-junction photovoltaic cells and reversible thermoelectric materials to approach their theoretical efficiency limit.
Design and numerical investigation of cadmium telluride (CdTe) and iron silicide (FeSi2) based double absorber solar cells to enhance power conversion efficiency
Divergent Solid-state Conversion Pathways in Evaporated All-perovskite Tandem Solar Cells
Empa – Swiss Federal Laboratories for Materials Science and Technology（瑞士联邦材料科学与技术研究院）；Zurich University of Applied Sciences（苏黎世应用科学大学）；ETH Zürich（苏黎世联邦理工学院）
Relating Band Edge DOS Occupancy Statistics Associated Excited State Electrons Entropy Generation to Free Energy Loss and Intrinsic Voc Deficit of Solar Cells
该研究将带边 DOS 占据及激发态电子熵与太阳能电池自由能损失和本征 Voc 亏损关联，指出带边 DOS 工程是突破辐射复合损失、优化性能的新维度。
Cataloguing MoSi$_2$N$_4$ and WSi$_2$N$_4$ van der Waals Heterostructures: An Exceptional Material Platform for Excitonic Solar Cell Applications
二维（2D）材料范德华异质结构（vdWHs）提供了一条革命性的路线，以实现超越传统硅基PN结太阳能电池的高性能太阳能转换器件。尽管近年来取得了巨大的研究进展，但具有优异激子太阳能电池转换效率和光学性质的vdWHs的搜索仍然是一个开放的理论和实验探索。在这里，我们表明，由MoSi $_2$ N $_4$和WSi $_2$ N $_4$单层组成的vdWH家族为开发高性能的双激子太阳能电池和光子器件提供了一个引人注目的材料平台。利用第一性原理计算，我们构造并分类了51种MoSi $_2$ N $_4$和WSi $_2$ N $_4$基[（Mo，W）Si $_2$ N $_4$ ] vdWH，它们由各种金属、半金属、半导体、绝缘和拓扑二维材料组成.有趣的是，MoSi $_2$ N $_4$ /（InSe，WSe $_2$）被鉴定为II型vdWH，其具有达到远超过20%的优异的激子太阳能电池功率转换效率，这与现有技术的硅太阳能电池竞争。（Mo，W）Si $_2$ N $_4$ vdWH系列在可见光和紫外光区都表现出很强的光吸收。在（Mo，W）Si $_2$ N $_4$/ $α_2$ -（Mo，W）Ge $_2$ P $_4$ vdWHs中可以实现超过40%的超大峰值紫外吸收，接近自支撑2D材料的最大吸收极限。我们的发现揭示了（Mo，W）Si $_2$ N $_4$ vdWH在设计最终紧凑的…
激子半导体已经成为光伏应用的研究主题数十年。其中，基于有机聚合物和小分子的太阳能电池目前的功率转换效率（PCE）已超过19%。随着有机光伏材料（OPV）的日益成熟，二维过渡金属二硫属化物（TMDC）等强激子无机半导体材料的出现，由于其高的光学常数、稳定的无机结构和亚nm的薄膜厚度，激发子太阳能电池的研究又重新受到人们的关注。虽然已经发布了几份关于基于TMDC的PV的报告，但在一个太阳AM1.5G照明下实现高于6%的功率转换效率仍然具有挑战性。在这里，我们进行了全面的光学和电子分析的设计，结构和性能的单层TMDC为基础的，单结激子PV。我们的计算模型与优化性能预测的PCE为9.22%的超晶格器件结构。我们的分析表明，虽然二维激子太阳能电池的PCE可能被限制在<10%，但我们提出的设计可以实现> 100 W g-1的比功率，使它们在航空航天，分布式遥感和可穿戴电子产品中具有吸引力。
