多重激子效应在III-V族量子点中的实现及其在新型纳米结构光伏器件中的应用

The principle and application research on new concept solar cells has been the frontier of modern photovoltaic science and technology. This project has proposed the novel fundamental research on the realization and application of hot carrier quantum dot sensitized solar cell with III-V group semiconductors, which has been based on the multiple exciton generation (MEG) effect on the usage of high energy photons that increases the general conversion efficiency of the solar cells. On the one hand, the III-V group semiconductor quantum dots, e.g., the InAs quantum dots, have advantages such as large absorption efficiency, tunable band gap in a broad range, strong radiation proof, very small electron effective mass and easily controllable growth. On the other hand, the project is based on substrate with broad band gap oxide nanostructured semiconductor, which has high stability, low requirement for the material purity and homogeneity, and simple fabrication methods. This project aims to achieve the controlled growth and band gap manipulation of the InAs based quantum dots by colloid chemical methods. It will carry on experimental investigation on the multiple exciton generation effect in InAs quantum dot structures and diminish factors from the defects (for example the surface state). The final purpose is to establish new solutions that effectively separate and collect multiple electron-hole pairs and build feasible models of high efficiency quantum dot sensitized solar cells based on multiple exciton generation effect. The deep through research of this project will hopefully introduce new vitality to the exploration of new type solar cells and accelerate the general development of photovoltaic science and engineering.

新概念太阳电池原理与器件应用探索研究已成为当代光伏科学与技术学科前沿。本项目提出进行多激子效应在热载流子III-V族半导体量子点敏化太阳电池上的应用创新基础研究，主要借助多激子效应对高能量光子的利用从而提高太阳电池转换效率这一特色，一方面充分利用以InAs为代表的III-V族半导体量子点吸收系数大，纳米结构带隙可调范围广，抗辐射性强，电子有效质量小和可控生长等优点，另一方面以宽禁带氧化物半导体纳米结构为基底，稳定性好，对材料纯度及均匀性等要求较低，制备简单。项目采取胶体化学等手段以实现多组分InAs基量子点可控生长和能带调控，开展InAs基量子点结构中多激子效应的实验研究，排除表面缺陷态等因素，建立有效分离和收集量子点体系中多电子- - 空穴对的新机制，最终摸索出基于多激子效应的高效量子点敏化太阳电池可行方案。本项目的深入研究将为新型太阳电池研发注入新活力，加快半导体光伏科学与工程的发展进程。

新概念太阳电池原理与器件应用探索研究已成为当代光伏科学与技术学科前沿。本项目针对此方面研究中多激子效应等新效应在半导体量子点敏化太阳电池上的应用进行创新基础研究。研究主要从几个方面进行：1.高性能半导体基底材料新纳米结构的设计与可控生长；2.双组分及多组分半导体材料在纳米基底上的原位可控沉积生长；3.半导体纳米结构在外电磁场等条件影响下的变化；4. 纳米复合结构材料结构及形貌参数对光电转换性质的影响。通过以上研究，建立了在大气环境下基于开放式电化学反应系统的多组分半导体材料快速原位沉积方法，可在氧化物半导体基底（TiO2等）上面快速制备PbS, CdSe等不同组分的半导体材料。所得的复合结构在敏化电池中取得了明显的转换效率（PbS 3.41,CdS 1.46%）。其次，利用电流逆注入退火在低温下制备了近单晶的TiO2纳米管阵列基底，并首次发现了化学刻蚀中光作用下纳米线阵列的弯曲现象，发现其与化学刻蚀在光照下半导体载流子激发引起的反应前沿方向改变有关。最后通过理论研究首次研究了纳米结构形貌参数对内量子效率的影响，着重研究了跟多重激子有关的短波区域，以优化的纳米线纳米结构为基础的异质结太阳电池效率可多收集38.25%的电流。总的来说，研究基本达到了目的，并且在此基础上进一步提供了扩展到广泛的其他材料和相关现象研究的可能性。