具有多载流子雪崩效应的半导体量子点/碳杂化纳米带的可控构筑及其光伏特性研究

The narrow band-gap semiconductor quantum-dots, excited by the light with high-energy, can generate multi-carrier phenomena, and thus they will have broad prospects in the cost-effective third-generation solar cells. However, their huge surface states can cause the recombination of photogenerated electron-hole pairs, and thus the actual conversion efficiency is quite low compared to their theoretical value. To solve the vital problem, we shall synthesize on a large-scale quantum-dots/carbon hybrid nanobelts via a simple low-temperature combustion synthesis method followed by a sulfide or selenide process. The photogenerated carriers can be separated effectively and transported rapidly by a heterogeneous interface effect. The quantum dots will be codoped with donor and acceptor, and the non-radiative recombination centers can be reduced by the surface segregation and mutual compensation effect of co-dopants, and correspondingly, the life of the photogenerated carriers can be prolonged. The size and composition of quantum dots will be modulated, and furthermore, some intermediate levels will be introduced in order to increase the response range and absorption coefficient of sunlight. As a result, the photoelectric conversion efficiency will be substantially increased. Fianally, a third-generation solar cell will be built with low cost and high conversion efficiency. The controlled synthesis of new types of quantum-dots/carbon hybrid nanobelts will be explored, the modulation mechanism of the deep levels and interface defects of the quantum dots will be established, the hybrid optoelectronic synergy mechanism will be revealed, and the relation between materials and device performance will be obtained. It will be provided the theoretical basis for the performance modulation of quantum dots and the technical support for the development of nanodevices.

窄带隙半导体量子点在高能光激发下能产生多载流子现象，以该材料构筑高效低成本的第三代太阳能电池具有广阔的前景。但巨大表面态会导致光生电子-空穴对重新复合，转换效率与理论值差距较大。针对此关键问题，我们拟采用简单的低温燃烧合成法并结合后续硫化和硒化工艺大规模合成量子点/碳杂化纳米带结构，利用异质界面的协同效应提高光生载流子的快速分离与转移；在量子点中实行施受主共掺杂，利用掺杂剂在其表面偏析及互补偿效应降低非辐射复合中心，增加光生激子寿命；引入中间能级并调制其尺寸、成份和分布，增加对太阳光的响应范围和吸收系数。最终大幅提高光电转换效率，并通过合适的器件构筑实现高效低成本的第三代太阳能电池。我们将探索新型量子点/碳杂化纳米结构的可控制备技术；建立量子点深能级及界面缺陷调控机制；揭示杂化结构的光电协同作用机理并获得与器件性能的内在本质关联。为量子点的性能调控奠定理论基础，并为器件的发展提供技术支持。

窄带隙半导体量子点在高能光激发下能产生多载流子现象，因此该材料具有高效的光电转换效率。但量子点的巨大表面态会导致光生电子-空穴对重新复合，转换效率与理论值差距较大。本项目通过低维半导体与碳的独特杂化结构的构建，利用半导体/碳纳米杂化结构的协同效应产生新奇的物理性能，以制作成新型的纳米器件。主要开展了以下三个方面的研究。首先，我们探索 CdSe、PbS和PbSe等II-VI族半导体与碳形成不同纳米结构的制备技术，改善材料性能。发展了利用低温燃烧合成法制备量子点/碳杂化纳米带结构；利用自行优化及改善的化学气相沉积法制备出碳包覆半导体一维纳米线芯壳异质结构的制备技术，以及石墨烯包覆一维纳米线芯壳异质结构的制备技术。其次，探索并提出光生载流子在量子点/碳杂化纳米结构异质界面的分离与转移机制。最后，探索外界电场、光场和应力场等对量子点/碳杂化纳米结构电输运特性的影响，从而构筑新型纳米结构电阻开关、光伏器件、光电探测及自供能光电探测器件、应力传感器件。揭示出杂化结构的协同作用机理并获得与器件性能的内在本质关联。这些研究对探索半导体纳米结构材料的性能和新型纳米器件的制作与应用具有重要意义。为量子点的性能调控奠定理论基础，并为其器件的发展提供实验依据。