原位构筑超快载流子传输特性的Si/TiO2异质结构及其光阳极性能研究

Solar water splitting provides a potential solution to the pending global energy and environmental crisis. Si is a promising material for photoelectrode in a photoelectrochemical system because of its several advantages such as high purity, large single crystals, effective conductivity, optimal for solar spectrum and natural abundance. However, it is not suitable to use as photoelectrode directly due to its self-passivation and corrosive reactions in electrolyte. Therefore, one method is to introduce a heterogeneous coating on Si surface to improve its efficiency and stability. Recently, Si/TiO2 photoelectrodes draws our attention back due to the innovation of transparent conductive TiO2 coatings, which is essentially independent of TiO2 thickness. However, the carriers transfer efficiency is still low due to the recombination at the interface of Si/TiO2 heterogeneous and quantum-tunneling effect induced by insulating SiO2 layer. This proposal aims at in-situ fabricating Si/TiO2 heterogeneous interface by constructing TiO2 nanoepitaxial growth on Si substrate. The Si and TiO2 are connected by chemical bonds. The removed SiO2 and nearly defect-free interfaces can cause carriers ultrafast transferring through the heterogeneous interface, which can solve the problems of the carrier recombination and quantum-tunneling effect. Firstly, a dense TiO2 layer is constructed on Si substrate by investigating the intrinsic properties of Si surface and nanoepitaxial growth conditions. Secondly, the dynamic process of the carriers transferring through the heterogeneous interface is demonstrated by studying the relationship between the interfacial properties and carriers transfer process. Finally, catalysts will be deposited on Si/TiO2 to fabricate photoanode. The essential relationship of interfacial properties-carriers transfer process-electrode properties needs to be studied in order to fabricate an efficient and stable photoanode. Through these investigations, our target is to provide experimental and theoretical foundations for developing highly efficient photoanode materials of solar water splitting.

光解水有望解决能源危机与环境恶化问题，具有重要的研究价值，然而目前效率较低。半导体Si是极富潜力的光解水电极材料，近年来由于在保护层的研究方面取得突破，使其再次受到广泛关注。但存在界面缺陷导致载流子复合及绝缘层SiO2导致量子隧穿的问题，严重影响Si电极效率。针对上述问题，本项目提出通过晶面诱导外延生长的方式、原位构筑Si/TiO2异质结构的解决方案，以化学键直接键合Si和TiO2保护层，既可避免绝缘层SiO2产生，又可降低界面缺陷密度，解决载流子界面复合及量子隧穿的问题。研究内容：1）研究Si表面的本征特性及晶面诱导生长条件，实现原位构筑致密的TiO2保护层；2）研究界面性质对载流子传输的影响，阐明载流子界面传输的动力学过程；3）构筑负载Ni催化剂电极，研究界面性质-载流子传输过程-电极性能之间的构效关系，制备出高效、稳定的光阳极。为开发高效的光解水电极材料提供一定的实验基础和理论依据。

光解水有望解决能源危机与环境恶化问题，具有重要的研究价值，然而目前效率较低。半导体Si是极富潜力的光解水电极材料，但使用Si为光解水材料时，存在界面缺陷导致载流子复合及绝缘层SiO2导致量子隧穿的问题，严重影响Si电极效率。针对上述问题，我们通过晶面诱导外延生长的方式、在单晶Si的表面，原位构筑Si/TiO2异质结构，以化学键直接键合Si和TiO2保护层。结果显示锐钛矿型TiO2的(004)晶面很好的延单晶硅的(001)表面定向生长，而晶格与晶型不匹配的金红石型TiO2无法进行异质界面生长，并易于剥离。采用外延生长方式制备的Ni/TiO2/Si光阳极，表现出良好的载流子传输能力和较高的载流子注入和分离效率。其光电流密度为31 mA/cm2，是Ni/TiO2/SiO2/Si光阳极的11倍。该光阳极可以在1 M KOH的溶液中稳定工作1500 min以上，说明该光阳极的性质比较稳定，异质界面生长的薄膜质量较好，可以保护硅基底。.Ni/TiO2/Si光阳极在工作时，需要对电极进行加1.0 V以上的偏电压，我们拟采用太阳能电池的方式进行加偏压。我们对钙钛矿太阳能电池进行了相关的研究工作。在Non-TiO2的电子传输层材料钙钛矿太阳能电池中，我们原位合成了一系列的SnS2、SnS2/SnS复合硫化物二维纳米材料，将其作为电子传输层材料制备钙钛矿太阳能电池，其效率可以超过18%。在HTL-free的碳基钙钛矿太阳能电池研究方面，我们研究了碳基对电极材料的开发和界面连接。与常规电池相比，HTL-free的碳基钙钛矿太阳能电池在稳定性方面有了大幅度的提高，课题组的碳基钙钛矿太阳能电池效率已达到16.41%，处于世界领先地位。.本项目共支持发表SCI论文18篇（1作及通讯），申请发明专利7项（3项授权）。获省级自然科学学术成果奖三等奖1次，市级自然科学学术成果一等奖2次，二等奖1次。培养研究生6人。