Probing the energetics and loss mechanisms in molecular solar cells using luminescnce

本提案旨在建立一个统一的框架来理解分子或纳米结构异质结太阳能电池效率的理论和实践限制。该方法是利用基于发光的技术、电测量和建模来量化和优化每个吸收光子的可用电功量。作为技术相关材料系统的例子，我们将研究聚合物：富勒烯，聚合物：纳米颗粒和染料敏化氧化物结构，目的是在一个框架内描述这些不同的异质结。我们的方法是通过所使用的材料和工艺的变化来控制异质结处电荷分离态的能量，检测和测量该状态的能量，并与吸收的光子能量和传递到外部电路的自由能进行比较。需要解决的特殊问题涉及到异质结介质介电常数的影响（通过比较所有有机异质结和杂化异质结）；微观组织的影响；以及对二元异质结和三元异质结的不同要求，以实现电荷分离。第二个目标是提高对基于发光的表征技术的理解，并找到这些技术的新应用。在分散异质结的情况下，如聚合物富勒烯太阳能电池，发光使我们能够研究不同重组机制的影响，特别是比较内部聚合物富勒烯界面上的重组和电极上的重组。这可能被证明是一种有价值的诊断方法，用于一系列光电器件。例如，在制造过程中原位应用于光伏器件的发光可以作为诊断工具来指示器件内能量损失的来源。我们已经聘请了一个工业项目合作伙伴来探索这一应用。

This proposal seeks to establish a unified framework for understanding the - theoretical and practical - limits to efficiency of molecular or nanostructured heterojunction solar cells. The approach is to quantify and optimize the amount of electrical work available per absorbed photon using luminescence based techniques, electrical measurements and modelling. As examples of technologically relevant material systems we will study polymer:fullerene, polymer:nanoparticle and dye sensitized oxide structures, with the aim of describing these different heterojunctions within a single framework. Our approach is to control the energy of the charge separated state at the heterojunction through variations in materials and processes used, detect and measure the energy of that state and compare with the absorbed photon energy and the free enrgy delivered to an external circuit. Particular questions to be addressed concern the effect of the dielectric permittivity of the heterojunction medium (by comparing all organic with hybrid heterojunctions); the effect of microstructure; and the difference in the requirements upon binary and ternary heterojunctions to enable charge separation. A second aim is to improve understanding of luminescence based characterization techniques and find new applications of the techniques. In the context of dispeersed heterojunctions such as polymer:fullerene solar cells, luminescence allows us to study the effect of different recombination mechanisms and compare in particular recombination at the internal polymer:fullerene interface with recombination at the electrodes. This could prove to be a valuable diagnostic method for a range of optoelectronic devices. For example, luminescence applied in-situ to photovoltaic device sduring manufacture can serve as a diagostic tool to indicate the sources of energy loss within the device. We have engaged an indutrial project partner to explore this application.