具有黄铜矿结构的高效超薄铜基化合物薄膜太阳电池研究

Cu-based compound with chalcopyrite structure thin film solar cells has attracted increasing attention for its high conversion efficiency, and has achieved significant improvement on device performance in recent years. Now this thin film solar cells has transferred into mass production and the cost of production need to be decreased. It is really important if the thickness of the absorber film is reduced to sub-micrometer because the usage of noble metals will be reduced greatly and the cost of production will be decreased greatly. However, the world record performance of ultra thin Cu-based thin film solar cells is only 12.6%, far from its theoretical limit, and there are still a lot of key problems to be solved. This proposal is aimed to fabricate an ultra thin solar cell with the efficiency above 14%. Combining with the numerical simulation, the defect density, grain boundary and energy band gap distribution which are the key factors limited the Voc and Jsc of solar cell in the ultra thin Cu-based solar cells will be systematic studied. As a result, the ultra thin solar cells with high conversion efficiency can be made clear. By studying the project, it not only can fabricate a ultra thin solar cell with the conversion efficiency above 14%, but can have a comprehensive understanding on the key factors limiting the efficiency of solar cell, and also the fundamental theory on opto-electronic process of multi-component compound semiconductor thin film solar cells can be enriched, which will be good to for the development of solar cells.

具有黄铜矿结构的化合物薄膜电池作为一种高性能太阳电池受到广泛关注，并取得很大发展。目前该电池已进入量产阶段。发展超薄电池有助于减少构成吸收层材料的贵金属的使用量，降低生产成本，其意义十分重大。然而，目前铜基黄铜矿结构超薄电池的世界最高转换效率只有12.6%，还十分落后于理论值。本项目以研制效率超过14%的铜基黄铜矿结构超薄电池为目标，结合数值模拟，通过精确控制薄膜的成分、碱金属钝化晶界、使用钝化层钝化背面场缺陷、以及设计超薄电池带隙梯度结构，系统研究限制铜基黄铜矿结构超薄高效电池开路电压和短路电流密度提升的吸收层中缺陷浓度、晶界、带隙结构等问题，掌握高效超薄电池的工作机制。通过本项目的研究，不但能研制出高效超薄铜基黄铜矿结构的薄膜电池，而且能深入解决超薄太阳电池中制约高效电池研发的关键因素，丰富多元化合物薄膜电池光电转换机理方面的理论，推动薄膜太阳电池的发展。

具有黄铜矿结构的铜基化合物薄膜太阳电池具有转换效率高、性能稳定等优势，目前已经开始产业化。如何更好的提高经济效益，需要降低电池组件的成本。超薄化太阳电池吸收层的厚度在降低器件成本、提高太阳电池经济效益方面具有重要意义。但太阳电池的效率因吸收层变薄后出现对可见光吸收不充分、载流子利用率等原因而出现显著降低。因此理解与掌握超薄吸收层的设计与生长及载流子输运等是超薄铜基化合物薄膜太阳电池的重要研究课题。本项目研究了具有黄铜矿结构的铜基化合物CIGS超薄薄膜的可控生长及超薄太阳电池，重点研究了提高载流子分离与收集的超薄吸收层生长、背界面电场调控及碱金属钝化晶界等。研究发现，高Ga存在会抑制薄膜(112)择优生长。当吸收层减薄到1μm时，此时吸收层是完全耗尽状态，器件中的载流子能获得较好的收集。由于在超薄电池中需要钝化的缺陷更多，外掺适量的Na可实现缺陷的钝化，载流子长波收集增强，超薄电池特性得到改善。同时发现在Mo背电极与CIGS吸收层之间添加宽带隙的CuGaSe2界面层，更利于载流子的收集，适合于超薄CIGS电池研制。通过协同调控，研制出效率为14.27%的超薄CIGS电池。在Adv. Sci.等期刊发表SCI文章28篇，其中一篇高被引论文。申请发明专利3项，培养毕业3名博士生、5名硕士生。组织PVSEC29中Area 4: Compound semiconductor PV分会等国际会议四次。