石墨烯/金属氧化物半导体异质结的构建及其光电转换效率增强机制研究

The dye-sensitized solar cells (DSSCs) have become the potential replacement of Si-based solar cells because of many advantages such as abundant materials, low costs, and simple processing techniques. The current research focus has been placed on how to enhance the photon-to-electron conversion efficiency of DSSCs. To solve the low efficiency problem of current DSSCs, we aim to controllably grow single crystal metal oxide microtubes on few-layered graphene and construct the graphene/metal oxide semiconductor heterojunctions, so that we are able to enhance DSSCs' conversion efficiency by coupling effects of heterojunction, light trapping, and hierarchical structure. We would systematically study the effects of the morphology of graphene and the assembly technique of single crystal metal oxide microtubes on the heterojunctions' structure and morphology, clarify the controlled growth mechanism of graphene/metal oxide semiconductor heterojunctions, and discover the relationships between the morphology of heterojunctions and the performance of DSSCs. Therefore, we can establish the conversion efficiency enhancement mechanisms of the fast electron-hole separation process in heterojunctions, the light trapping effect in microtubes, and the resistance reducing and efficiency enhancing theories of hierarchical structures. The outcomes of this work should be helpful to advance the basic research for solar cells in our country, develop a novel class of heterojunctions, and provide some new views and models for enhancing the photon-to-electron conversion efficiency of DSSCs.

染料敏化太阳能电池由于其原料丰富、成本较低、工艺简单和使用方便的优点，已成为硅太阳能电池的潜在替代品，目前的研究重点在于如何提高其光电转化效率。为了解决现有染料敏化太阳能电池光电转换效率低的缺点，本项目通过在少层石墨烯上可控生长单晶金属氧化物微米管而构建石墨烯/金属氧化物半导体异质结，将利用异质结、陷光效应和微纳米分级结构以提高其光电转换效率。系统研究石墨烯结构形态、单晶金属氧化物微米管组装工艺对异质结微观结构和形貌的影响规律，探索石墨烯/金属氧化物半导体异质结的可控生长机理；深入研究异质结结构形貌与染料敏化太阳能电池性能的内在关系，揭示其在异质结电子空穴快速分离过程、微米管陷光效应和微纳米分级结构降阻增效效应等方面增强光电转换效率机制。该研究成果有利于提高我国太阳能电池的基础研究水平，为发展一类新型的异质结材料，并为提高染料敏化太阳能电池的光电转化效率提供新思路和理论模型。

半导体纳米材料在光电化学过程中起着重要作用。本项目对光电化学反应中光电转换增强机理进行深入研究，取得一些非常有意义的成果，基本掌握石墨烯、碳量子点、金属颗粒、氧化物纳米材料的可控合成关键技术，并构建多种不同的异质结，表征这些纳米材料的形貌和结构，利用多种手段对光电转换性能进行深入表征，通过研究光催化、光电催化、染料敏化太阳能电池、光电探测器等具体对象，探索中光生载流子产生、传输、分离、转化等过程，获得光电转换增强的规律。重要结果包括：1. 发现并解释了氧化石墨烯和贵金属颗粒与半导体纳米材料形成异质结，增强光电转换及催化能力；2. 发现了碳量子点与BiVO4纳米材料之间的协同效应可以获得BiVO4体系的钒酸铋体系中最高纪录的外加偏压光电转换效率（ABPE）2.29%，3.发现新型BiOI-BiVO4光阳极的光电流高达3.27 mA/cm2，远高于各自的1.23和0.15 mA/cm2，提出p-n结增加可见光的吸收范围和促使光生电子空穴分离的解释。在本项目的经费资助下，还扩充了研究内容，对氧化物的光电性能、储能性能进行了一些前沿性的探索，也取得可喜的阶段性成果。在本项目的支持下，发表SCI论文39篇，其中ESI高被引论文2篇，影响因子超过10.0的有10篇，最高影响因子为29.518，)获批发明专利5项，申请发明专利4项，培养了赵传熙等多位青年骨干教师和张龙、强鹏飞等多名研究生，完成任务书上的各项指标。