Understanding Multiple Exciton Generation and Charge Extraction in All-Inorganic Nanostructured Solar Cells from first principles

这一提议研究了一种变革性的太阳能转换新范式：1.一种高效的多重激子产生(MEG)途径2。相应的电荷提取挑战3。在全无机纳米结构太阳能电池中，MEG最近在纳米颗粒(NPs)中被观察到，并且不受31%的理论太阳能转换限制。利用基于密度泛函理论的方法，系统地研究了Si和Ge Np基全无机太阳电池的MEG和电荷提取过程，重点研究了Np表面和电荷输运。申请者想要回答与以下问题相关的问题：1.相互竞争的MEG理论目前有三种相互竞争的理论来解释MEG的小体积价值是如此之大。哪一个是正确的？计算包括激子-激子相互作用在内的三个不同框架内的NP谱将允许与实验研究进行比较，以试图确定MEG的最终正确理论。NP表面效应NP表面重构和钝化对NPs的电子结构和光谱有何影响？它是如何影响电荷传输的？如何选择表面钝化来优化相互竞争的设计要求，既要保持量子限制以支持MEG过程，又要确保足够强的耦合以提取电荷？3.NP-NP耦合在现实的太阳能电池结构中，NP彼此相对较近。NPs之间的电子耦合在多大程度上影响它们的光谱？NP-NP的分离如何影响电荷提取？理想情况下，这个项目不仅将导致对纳米颗粒中MEG过程的彻底了解，而且应该允许对如何在现实的太阳能电池应用中优化MEG和电荷提取过程的效率进行定性预测。

This proposal investigates a transformative new paradigm of solar energy conversion:1. a high efficiency Multiple Exciton Generation (MEG) pathway2. the corresponding challenge of charge extraction3. in all-inorganic nanostructured solar cellsMEG was recently observed in nanoparticles (NPs) and is not subject to the 31% theoretical solar energy conversion limit. It is planned to utilize density functional theory based methods to explore systematically the MEG and charge extraction processes in Si and Ge NP-based all-inorganic solar cells, with focus on the NP surfaces and charge transport. The applicant wants to answer the following questions related to:1. Competing MEG theoriesAt present there are three competing theories to account for the MEG being enhanced so much over its small bulk value. Which is the correct one? Calculating the NP spectra including exciton-exciton interaction within the three different frameworks will allow a comparison with experimental studies, in an attempt to identify the ultimately correct theory of MEG.2. NP surface effectsHow do NP surface reconstruction and passivation influence the electronicstructure and spectra of the NPs? How does it influence the charge transport? How should the surface passivation be chosen to optimize the competing design requirements of preserving quantum confinement in support of the MEG process, while still ensuring a strong enough coupling for charge extraction?3. NP-NP couplingIn realistic solar cell architectures the NPs are relatively close to each other. Towhat extent does the electronic coupling between NPs influence their spectra? How does the NP-NP separation influence the charge extraction?Ideally, this project will not only lead to a thorough understanding of the MEG process in nanoparticles, but should allow for qualitative predictions about how to optimize the efficiency of both the MEG and charge extraction processes in realistic solar cell applications.