Wippermann S, Vörös M, Rocca D, Gali A, Zimanyi G, Galli G
Department of Chemistry, University of California, Davis, California 95616, USA and Department of Physics, University of California, Davis, California 95616, USA.
Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary.
Phys Rev Lett. 2013 Jan 25;110(4):046804. doi: 10.1103/PhysRevLett.110.046804. Epub 2013 Jan 24.
We present density functional and many body perturbation theory calculations of the electronic, optical, and impact ionization properties of Si nanoparticles (NPs) with core structures based on high-pressure bulk Si phases. Si particles with a BC8 core structure exhibit significantly lower optical gaps and multiple exciton generation (MEG) thresholds, and an order of magnitude higher MEG rate than diamondlike ones of the same size. Several mechanisms are discussed to further reduce the gap, including surface reconstruction and chemistry, excitonic effects, and embedding pressure. Experiments reported the formation of BC8 NPs embedded in amorphous Si and in amorphous regions of femtosecond-laser doped "black silicon." For all these reasons, BC8 nanoparticles may be promising candidates for MEG-based solar energy conversion.
我们展示了基于高压体相硅相的具有核结构的硅纳米颗粒（NPs）的电子、光学和碰撞电离性质的密度泛函及多体微扰理论计算。具有BC8核结构的硅颗粒表现出显著更低的光学带隙和多激子产生（MEG）阈值，并且与相同尺寸的类金刚石颗粒相比，MEG速率高一个数量级。讨论了几种进一步减小带隙的机制，包括表面重构与化学、激子效应和嵌入压力。实验报道了嵌入非晶硅以及飞秒激光掺杂“黑硅”的非晶区域中的BC8 NPs的形成。基于所有这些原因，BC8纳米颗粒可能是基于MEG的太阳能转换的有前景的候选材料。
