纳米异质结阵列的构筑、界面调控实现太阳电池中载流子的高效分离和收集

The arrayed nanostructures are widely used to enhance the collection efficiency of photo-generated carriers in solar cells. However, the difficulty on the controllable fabrication of heterojunctions and interface modulation in the nanoscale restrict their further applications. Aimed to resolve these problems, we propose this study as follows: Firstly, the large-scale ZnO nanodot arrays are fabricated on the conductive glass substrate (ITO) through the micor-fabrication techniques. Subsequently, the ZnO nanorod arrays with controllable length, rod-rod distance and density can be obtained through the hydrothermal growth. The controllability benefits mainly from the restriction effects of pre-formed ZnO nanodot arrays. Beside this, we also plan to fabricate a large-scale ZnO network arrays using the versatile nanosphere lithography. Next, the interfaces of two ZnO based nanostructure arrays will be modulated through the ion-exchange reactions to form a type II core-shell heterojunctions. Such type II heterojunctions have band gaps that form a stepwise energy alignment at the interface, which can eliminate the surface states and interface states effectively. Finally, the fundamental researches on the nanoscale photo-electric separation and charge transport process between the type II interfaces will also be carried out. The above research project is proposed based on our previous research works and the thoroughly literature investigations. Therefore, we think there will be a remarkable conversion efficiency improvement by introducing our new type nanostructure arrays in heterojunction based solar cells.

阵列化纳米结构在异质结太阳电池中起着分离和直接传输载流子的重要作用，然而在目前的应用中存在纳米尺度异质界面难以构筑和常规界面无法实现载流子高效分离和收集的问题。为此，本项目提出利用微加工技术大面积构筑ZnO纳米点阵结构；在生长位点及水热生长条件的限制和调控双重作用下，制备长度、间距和密度可控的ZnO纳米棒阵列结构；并在此基础上利用纳米球模板（Nanosphere lithography）技术大面积构筑ZnO网格状阵列结构；通过离子交换反应在这两类ZnO阵列化结构表面构筑II型核壳异质界面，在界面处形成具有梯度的能级结构，构筑新型纳米尺度异质结，实现光生载流子在其界面的有效分离和直接传输，从而实现光生载流子的高效收集；开展基础研究对纳米尺度异质界面间的光电分离、传输过程和机制进行研究；建立纳米尺度下表面界面光电分离与传输机制；使基于异质结构太阳电池的光电转换效率有较大幅度的提升。

本项目主要利用纳米球模板（Nanosphere lithography)技术大面积构筑了ZnO空腔阵列结构，并在此基础上构筑了高度有序的ZnO/Cu2O异质结薄膜光伏器件，这种高度有序的纳米阵列结构可以大幅提高异质结面积，其短路电流（Jsc）和光电转换效率较传统的双层薄膜异质结光伏器件均有较大程度的提高；通过阳离子交换反应制备ZnxCd1-xSe@ZnO核壳纳米线阵列结构，这种II型的异质结界面可以提高光生载流子的分离效率，从而提高ZnO纳米线阵列基光伏器件的光电转换效率；在FTO导电玻璃基底上构筑了垂直于基底生长的TiO2纳米线阵列，通过金纳米晶的引入，利用其表面等离子共振效应可以使短路电流密度得到提升，器件的转换效率也有一定程度的提高；定点生长高度垂直于导电基底ZnO纳米线阵列的研究工作也取得初步成果，深刻认识到高度取向ZnO纳米点阵的获取是保证ZnO纳米线垂直于基底生长的重要前提，目前我们已经能够利用磁控溅射技术制备取向性较好的ZnO薄膜，为我们定点生长高度取向的ZnO纳米线阵列提供了突破方向和研究基础；这些研究工作的开展为我们利用阵列化纳米结构增强光生载流子的分离和收集效率的研究思路提供了可行性。