新型石墨烯/氮化硼/砷化镓范德华异质结太阳能电池

Distinct from traditional Schottky diode, the barrier height of graphene/semiconductor Schottky diode is highly tunable as the Fermi level of graphene and semiconductor can be adjusted independently benefiting from the nature of van der Waals contact, the low density of energy states near Dirac point and small screening length of graphene. Reported results have proved that tuning the Fermi level of graphene can largely improve the performance of graphene/semiconductor heterostructure solar cells. While because of the charge transfer between graphene and semiconductor substrate, the range of Fermi level tuning in graphene is limited. In this project, choosing GaAs as the substrate semiconductor material, we propose inserting h-BN into the interface of graphene/GaAs to suppress the charge transfer when forming the heterojunction. The barrier height is expected to be increased by the insulating interface h-BN. The influence of the thickness of h-BN on charge transfer properties and recombination properties will be studied by electrical measurements including current-voltage and capacitance-voltage characteristics. The charge separation and collection properties will be investigated using Raman and transient PL measurements. And the Fermi level tuning effect dependent on the thickness of h-BN will be studied by employing gate effect structure. Based on these studies, we believe we can get graphene/h-BN/GaAs solar cell device with high power conversion efficiency. The results obtained in this project are very important for high performance two-dimensional materials based device design.

石墨烯的费米能级可调为石墨烯/半导体异质结太阳能电池的设计带来了独特优势，已有的实验结果通过化学掺杂和电场调节证明了石墨烯费米能级调节对电池性能的巨大影响。但由于石墨烯与半导体衬底之间的电荷转移，石墨烯费米能级调节范围受到严重限制。本项目选择性能优异的砷化镓作为衬底，在石墨烯/砷化镓异质结界面上增加原子层厚度的二维六方氮化硼抑制电荷转移以获得势垒高度更高的范德华异质结，利用电学测试以及拉曼测试、瞬态PL测试研究二维氮化硼厚度对结势垒高度的影响以及对界面载流子传输与复合的影响，研究二维氮化硼厚度对石墨烯费米能级调节范围的影响，并在这些研究的基础上获得高效率的石墨烯基太阳能电池器件。本项目针对石墨烯/半导体异质结中的特殊物理，在石墨烯/氮化硼/砷化镓全新材料体系中研究范德华二维材料异质结的界面电学特性，对高性能二维材料异质结器件的设计具有重要意义。

石墨烯材料的能带结构决定了石墨烯的电学性能可调制性，已有的报道已经说明化学掺杂或者电场掺杂均可以改变石墨烯材料以及器件的电学性能。在石墨烯/半导体异质结器件中，由于石墨烯与半导体衬底之间的电荷转移，石墨烯费米能级调节范围受到严重限制。本项目在石墨烯/砷化镓异质结界面上增加原子层厚度的二维六方氮化硼抑制电荷转移以获得势垒高度更高的范德华异质结，结合石墨烯掺杂、表面等离子增强等手段最终获得高性能的石墨烯/砷化镓范德华异质结器件。.本项目利用电学测试以及拉曼测试、瞬态PL测试等手段研究二维氮化硼厚度对结势垒高度的影响以及对界面载流子传输与收集的影响，研究二维氮化硼厚度对石墨烯费米能级调节范围的影响，并根据所得到的实验规律设计高性能的石墨烯/半导体异质结器件。本项目主要结果包括：通过界面二维氮化硼介电层的加入，得到了电性能更好的石墨烯/半导体异质结太阳能电池以及光电探测器；首次获得了石墨烯/薄膜碲化镉异质结太阳能电池，并通过光掺杂提高了石墨烯/碲化镉太阳能电池的转化效率，提升比例约50%；设计并获得了高探测度的自驱动型二硫化钼/氮化硼/砷化镓光电探测器，通过在二硫化钼/砷化镓异质结器件的界面上插入二维氮化硼层，提高了二硫化钼/砷化镓异质结器件的势垒高度并降低暗态电流，进一步结合硅量子点引入的光掺杂效应，我们获得了探测度最高的二硫化钼相关光电探测器；通过将表面等离激元应用在石墨烯/半导体异质结中，将8.83%转化效率的石墨烯/砷化镓异质结提升到11.8%，再结合化学掺杂以及表面减反射共同作用，获得了性能稳定的转化效率16.2%的石墨烯/砷化镓异质结太阳能电池。.本项目工作探索了界面电性能调制在石墨烯相关二维异质结器件中的应用，并通过一系列测试阐明了界面介质层的作用机制，为未来更高性能的石墨烯相关二维材料器件的设计提供了理论基础和实验基础。本项目相关工作工发表SCI论文7篇，总影响因子大于40，其中影响因子大于10的论文2篇。