Eggimann Hannah J, Patel Jay B, Johnston Michael B, Herz Laura M
Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK.
Nat Commun. 2020 Nov 2;11(1):5525. doi: 10.1038/s41467-020-19268-w.
Organic semiconductors are commonly used as charge-extraction layers in metal-halide perovskite solar cells. However, parasitic light absorption in the sun-facing front molecular layer, through which sun light must propagate before reaching the perovskite layer, may lower the power conversion efficiency of such devices. Here, we show that such losses may be eliminated through efficient excitation energy transfer from a photoexcited polymer layer to the underlying perovskite. Experimentally observed energy transfer between a range of different polymer films and a methylammonium lead iodide perovskite layer was used as basis for modelling the efficacy of the mechanism as a function of layer thickness, photoluminescence quantum efficiency and absorption coefficient of the organic polymer film. Our findings reveal that efficient energy transfer can be achieved for thin (≤10 nm) organic charge-extraction layers exhibiting high photoluminescence quantum efficiency. We further explore how the morphology of such thin polymer layers may be affected by interface formation with the perovskite.
有机半导体通常用作金属卤化物钙钛矿太阳能电池中的电荷提取层。然而，面向太阳的前分子层中存在寄生光吸收现象，太阳光在到达钙钛矿层之前必须穿过该层，这可能会降低此类器件的功率转换效率。在此，我们表明，通过将光激发聚合物层中的激发能高效转移至下层钙钛矿，此类损耗可以消除。实验观察到一系列不同聚合物薄膜与甲基碘化铅钙钛矿层之间的能量转移，以此为基础对该机制的效率作为有机聚合物薄膜层厚度、光致发光量子效率和吸收系数的函数进行建模。我们的研究结果表明，对于具有高光致发光量子效率的薄（≤10纳米）有机电荷提取层，可以实现高效能量转移。我们进一步探究了此类薄聚合物层的形态如何受到与钙钛矿形成的界面的影响。
