快电子传输氧化锌基复合光阳极的制备，表面改性及其染料敏化太阳能电池性能及机理研究

Compared with the conventional solar cells, dye-sensitized solar cells (DSCs) are thought to be advantageous as a photovoltaic device possessing both practicable high efficiency and cost effectiveness. However, a further increase in conversion efficiency has been limited by energy loss due to recombination between electrons and either the oxidized dye molecules or electron-accepting species in the electrolyte during the charge transport process. ZnO-based dye-sensitized solar cell (DSSC) is one of the most promising candidates, which has approximately the same band gap and band position as TiO2, however, a high electron mobility, low combination rate, and good crystallization into an abundance of nanostructures. Many efforts have been made on ZnO-based DSCs with either nanocrystalline films or films consisting of various nanostructures that are highly efficient in electron transport and/or photon capture. However, so far, the results obtained for dye-sensitized ZnO solar cells have still shown relatively low overall conversion efficiencies when compared with TiO2-based systems. The limited performance in ZnO-based DSCs may be explained by the instability of ZnO in acidic dye (i.e., protons from the dyes cause the dissolution of Zn atoms at ZnO surface, resulting in the formation of excessive Zn2+/dye agglomerates) and the slow electron-injection kinetics from dye to ZnO. The electron-injection efficiency is determined by the electronic coupling between the dye and semiconductor, and it is also judged by the relative energy levels of the dye and semiconductor, the residential life time of photogenerated electrons in the dye molecules, and the density of electron- accepting states in the semiconductor. In this project, for further electron-injection efficiency improvement, a combination method of ZnO-based composite photoanode and a surface modification was used. Some conductor or semiconductors( for example, MWCNTs, grapheme, ZnFe2O4，CuBi2O4) were chosen to fabricate a composite photoanode with ZnO, which can provide straight routes to facilitating electron transfer and suppressing recombination rate by reducing grain boundaries and the traveling length of photoelectrons before reaching the back contact, leading to the increase of open-circuit voltage, thus improving the photoelectric conversion efficiency of the DSSC. Moreover, Surface modification as a simple but effective method for reducing the reaction between ZnO and dyes and increasing the adsorption of organic dyes, enhances the polarity of the ZnO surface to form strong hydrogen bonds with oxygen functional groups and suppresses the formation of Zn2+/dye agglomerates. Furthermore, improving electron transport within the film, electron-injection efficiency and retarding recombination at the interfaces could also be achieved by interfacial modifications. Thus, in this project, we introduced some simple surface modification methods, such as air plasma treatment, thioacetamide (TAA) solution spray, which can adjust the surfacial chemical and charged situation, decrease the hydrogen-related defects in ZnO-composite photoanode, and therefore developing the photoelectric conversion efficiency of the DSSC. Besides, in this project, a further study on the mechanism of interface reaction will be carried out to determine the influence factors of surface treatment on the rate of electron-injection and electronic-collection efficiency. The successful implementation of this project will not only provide a practical path for improvement the efficiency of dye-sensitized solar cell, but will enrich the dye-sensitized solar cell research system.

虽然ZnO基染料敏化太阳能电池(DSSCs)光电转换效率目前尚不如人意，但因其具有较高电子迁移率和丰富形貌等众多优点，仍是DSSCs最具发展潜力的研究体系。限制ZnO基DSSCs光电转化效率进一步提高的原因来自ZnO在酸性染料中的化学不稳定性及从染料分子到光阳极的电子注入效率较低问题。本申请项目拟从如何提高电子注入效率入手，选择能够提高电子传输速率，延长光生电子寿命，降低内电阻的材料（如碳纳米管，石墨烯，p型无机半导体材料）与ZnO形成复合光阳极，并结合低温等离子体处理，有机表面改性剂表面喷涂等改性手段，改变ZnO基复合光阳极的界面属性，减少氢缺陷，降低Zn2+/染料团簇的形成机率，改善其在酸性介质中的化学稳定性，并进一步研究电池界面反应机理，确定表面处理对电子注入效率及电子收集的影响规律。本项目的实施将为提高DSSCs效率提供切实可行的有效路径，为这一体系的深入研究提供更多的理论依据。

ZnO基纳米结构染料敏化太阳能电池虽具有众多优点，但目前仍存在效率较低，稳定性较差等问题需要解决。限制ZnO基染料敏化太阳能电池光电转化效率进一步提高的主要原因来自ZnO在酸性染料中的化学不稳定性及电子从染料分子注入到ZnO半导体材料的效率较低等问题。本项目从提高电子注入效率入手，选择能够提高电子传输速率的材料（多壁碳纳米管），能够与ZnO形成p-n异质结并抑制电子复合，提高电子注入效率的无机半导体材料（ZnFe2O4，CuBi2O4，NiO，Cu2O）与ZnO形成了复合光阳极，达到优化电池结构，有效提高电子迁移速率，抑制电子重新复合的目的。利用1H,1H,2H,2H-全氟癸基三乙氧基硅烷表面涂层及硫代乙酰胺（TAA）对ZnO表面改性，改变了ZnO基复合光阳极的微结构属性，减少了氢缺陷，除了去ZnO 基复合光阳极表面覆盖的多余正电荷，改变了ZnO 表面的化学特性及电荷属性，降低了Zn2+/染料团簇的形成机率，从而提高了电子注入效率及电池性能，其相应的光电转化效率都有了不同程度的提高。并进一步通过研究界面特性与光电转化性能之间的关系及电池界面反应，确定了表面处理对电子注入效率及电子收集的影响规律。本项目的成功实施不仅为提高ZnO基染料敏化太阳能电池效率提供切实可行的路径，更将丰富染料敏化太阳能电池的研究体系和理论基础。研究成果发表SCI收录论文14篇，申请专利1项，获得新疆维吾尔自治区自然科学二等奖，培养硕士研究生5名。