自组装太阳能电池（二）

The highly efficient photon-to-electron conversion in Photosynthesis is deeply related with the highly ordered supramolecular hierarchical structures, which are self-assembled under direction of the Photosynthetic proteins. In this proposal, we first design a series of new building blocks, namely molecular heterojunctions and nano-heterojunctions by covalently linking both the structural directing units and the n-type and p-type organic semiconductors, both having high molar extinction coefficients and broad absorption range covering the near IR region of the solar spectrum. We then develop new approaches to control the self-assembly of these molecular/nano-heterojunctions, constructing electron-transfer chains and redox-gradient along the electron-transfer chain to carry out the unidirectional electron-transfer and highly efficient charge-seperation. Furthermore, we develop new methods to prepare the nano-arrays of the molecular and nano-heterojunctions on the transparent conductive oxides (TCO) to achieve highly ordered one-dimensional pi-pi stacking of the n-type and p-type organic semiconductors seperately and the double-cables for the positive and negative charge carriers to transport highly efficiently across the active layer. Accordingly, we aim to mimic the highly ordered hierarchical structures through supramolecular constructions of the electron-transfer chains, redox-gradient and double cables perpedicular to the TCO surface. These newly Photosynthesis-mimicking assemblies not only have the structural basis of the Photosythesis but also show photon-to-electron conversion. Utilizing these newly synthesized assemblies as the active materials, we propose herein a new kind of solar cells e.g. self-assembling solar cells (SA-SCs), which is distinctly different in both the active materials and the device structures to the currently reported organic/polymer solar cells (OSCs/PSCs) or dye-sensitized solar cells (DSSC). Accordingly, SA-SCs open a new way toward highly efficient photon-to-electron conversion. Finally, we will carry out the in-situ studies on the relationship between the supramolecular structures/nano-arrays and the photovoltaic properties, developing the basic models and principles for the SA-SCs.

天然光合作用体系是自然界利用光能的典范，其高度有序的自组装超分子结构是实现高效光电转换的重要基础。本申请以太阳能利用与转化为功能导向，选取高光敏响应的有机半导体单元和可控组装引导单元，设计合成分子异质结与纳米异质结组装基元；建立分子可控组装新方法，构筑电势梯度及电荷定向分离与转移通道，实现高吸光效率、宽光谱覆盖和高效的电荷分离；在透明导电玻璃（TCO）表面上，组装分子/纳米异质结的阵列化结构，构筑垂直于TCO玻璃表面的一维pi-pi堆积及载流子双传输通道，实现载流子定向、高效地传输；通过电荷定向分离与转移通道、载流子双传输通道和电势梯度的构筑，模拟天然光合作用体系实现高效光电转换的结构特性，构筑具有光电转换性能的可控组装新体系，开拓实现高效光电转换的新途径，研制自组装太阳能电池；在维纳层次上，原位关联研究自组装结构、阵列化结构与光电转换性能，建立自组装太阳能电池的理论模型和基本原理。

针对有机分子可否取代有机太阳电池中广泛使用的富勒烯受体材料的科学问题，展开了分子设计、聚集结构调控、电池器件制备等内容的研究。为了解决有机受体材料效率低下的问题，提出了“寡聚体分子骨架构型和极性侧链”协同调控分子聚集倾向及光活性层纳米结构的新思路——通过扭曲构型有效减弱分子聚集倾向，改善它与给体材料的相容性，来提高电荷分离效率；同时，利用扭曲结构具有的“立体匹配效应”，结合亲疏水侧链提供的亲疏水作用，来进一步增强扭曲分子形成有序堆积的能力，改善电子迁移率。从合成的一系列苝二酰亚胺基小分子受体材料中，通过选取合适的给体材料组合，在世界上，率先突破了非富勒烯基有机太阳能电池的4%的效率瓶颈，论文发表后，得到了国内外同行的广泛关注和认可，至今已被SCI引用150余次。通过设计分子端基，实现了激子高效分离与载流子定向传输的统一。深入系统地研究了溶剂添加剂调节形貌，改善激子分离与载流子传输的作用机理：发现提高加工溶剂和溶剂添加剂的沸点，有助于增强分子组装，提升电池性能；此外，也进一步发现，在残留于湿膜中的主加工溶剂和添加剂中溶解的给受体材料的量，是决定薄膜形貌的关键因素。通过精细调节溶剂氛退火技术的4个关键动力学参数，重新构建了受体材料的聚集结构，提升了电子迁移率，实现了非富勒烯有机太阳电池效率的大幅提升；发现溶剂添加剂可以精细调节活性层下表面中给受体的重量比，达到调节电子/空穴注入和效率的目的。率先提出了非富勒烯基全小分子太阳电池（Non-Fullerene All-Small-Molecule Solar Cells）的概念。