Thu Chawloon, Ehrenreich Philipp, Wong Ka Kan, Zimmermann Eugen, Dorman James, Wang Wei, Fakharuddin Azhar, Putnik Martin, Drivas Charalampos, Koutsoubelitis Aimilios, Vasilopoulou Maria, Palilis Leonidas C, Kennou Stella, Kalb Julian, Pfadler Thomas, Schmidt-Mende Lukas
Department of Physics, University of Konstanz, POB 680, 78457, Konstanz, Germany.
Cain Department of Chemical Engineering, 3307 Patrick Taylor Hall, Louisiana State University, Baton Rouge, LA, 70803, USA.
Sci Rep. 2018 Feb 23;8(1):3559. doi: 10.1038/s41598-018-21721-2.
ZnO is a widely used metal-oxide semiconductor for photovoltaic application. In solar cell heterostructures they not only serve as a charge selective contact, but also act as electron acceptor. Although ZnO offers a suitable interface for exciton dissociation, charge separation efficiencies have stayed rather poor and conceptual differences to organic acceptors are rarely investigated. In this work, we employ Sn doping to ZnO nanowires in order to understand the role of defect and surface states in the charge separation process. Upon doping we are able to modify the metal-oxide work function and we show its direct correlation with the charge separation efficiency. For this purpose, we use the polymer poly(3-hexylthiophene) as donor and the squaraine dye SQ2 as interlayer. Interestingly, neither mobilities nor defects are prime performance limiting factor, but rather the density of available states around the conduction band is of crucial importance for hybrid interfaces. This work highlights crucial aspects to improve the charge generation process of metal-oxide based solar cells and reveals new strategies to improve the power conversion efficiency of hybrid solar cells.
氧化锌是一种广泛应用于光伏领域的金属氧化物半导体。在太阳能电池异质结构中，它们不仅作为电荷选择性接触，还充当电子受体。尽管氧化锌为激子解离提供了合适的界面，但电荷分离效率一直相当低，且与有机受体的概念差异很少被研究。在这项工作中，我们对氧化锌纳米线进行锡掺杂，以了解缺陷和表面态在电荷分离过程中的作用。掺杂后，我们能够改变金属氧化物的功函数，并证明其与电荷分离效率直接相关。为此，我们使用聚合物聚（3-己基噻吩）作为供体，方酸染料SQ2作为中间层。有趣的是，迁移率和缺陷都不是主要的性能限制因素，而是导带周围可用态的密度对混合界面至关重要。这项工作突出了改善基于金属氧化物的太阳能电池电荷产生过程的关键方面，并揭示了提高混合太阳能电池功率转换效率的新策略。
