Optimising photochemical solar energy conversion in natural and artificial molecular systems.

在有机太阳能电池和自然光合作用系统中，将太阳光子转化为化学能或电能的潜在过程有许多共同的特征[1，2]。在这两种情况下，太阳光子都被一组分子吸收，然后光生激子扩散，解离成单独的电荷，并在器件或薄膜上分离电荷。自然光系统以高量子效率和低表观能量损失实现电荷分离，这表明光系统结构的各个方面可能对太阳能电池等人工系统有利。由于它们的结构被很好地理解，它们提供了吸引人的模型系统来研究光致电荷分离过程。对于光系统和太阳能电池，系统在照明或施加偏压(即发光)时发出的光携带有关光化学过程中涉及的不同过程的信息，是理解行为的关键[3]。该项目的目的是开发一个基于物理的光化学太阳能转换模型，该模型可并行应用于光系统和分子太阳能电池结构，并与实验数据一起使用，以更好地了解光系统的功能并优化太阳能电池的设计。该项目的目标如下：1)建立分子系统中现有的激发量子动力学模型，以模拟光系统或分子太阳能电池中的太阳光化学能转换过程。2)使用光吸收和光发射的实验测量以及该模型，以确定限制能量转换效率的因素并提出改进设计。3)将这些方法应用于最近发现的各种光系统，以了解它们如何在不损失量子效率的情况下，利用比标准光系统能量更低的光来驱动光化学反应[4]。4)利用所获得的理解来提出建议有机太阳能电池中分子的新排列可以通过减少非辐射能量损失来提高转换效率[3]。

The underlying processes that convert solar photons into chemical or electrical energy in organic solar cells and in natural photosynthetic systems have many features in common [1,2]. In both cases, solar photons are absorbed by an assembly of molecules, followed by diffusion of the photogenerated exciton, dissociation into separated charges and separation of the charges across the device or membrane. Natural photosystems achieve charge separation with high quantum efficiency and with low apparent energy losses, suggesting that aspects of the structure of photosystems could be beneficial for artificial systems like solar cells. Thanks to their well understood structure they provide appealing model systems in which to study the process of photoinduced charge separation. For both photosystems and solar cells, the light emitted by the system when illuminated or subject to applied bias (i.e. luminescence), carries information about the different processes involved in the photochemical process and is key to understanding behaviour [3].The aim of this project is to develop a physics-based model of photochemical solar energy conversion that can be applied in parallel to photosystems and molecular solar cell structures, and use it along with experimental data to better understand the function of photosystems and optimise the design of solar cells. The project has the following objectives:1) To develop an existing model of the quantum dynamics of excitations in molecular systems to simulate the process of solar photochemical energy conversion in either photosystems or molecular solar cells.2) To use experimental measurements of light absorption and emission in such systems along with the model to identify the factors limiting energy conversion efficiency and suggest improved designs.3) To apply the methods to recently discovered varieties of photosystem in order to understand how they manage to drive photochemical reactions with light of lower energy than standard photosytems without loss in quantum efficiency [4].4) To use the understanding gained to suggest new arrangements of molecules in organic solar cells that could lead to improvements in the conversion efficiency by reducing non-radiative energy losses [3].