Imaging Charge Transfer State Excitations in Polymer/Fullerene Solar Cells with Time-Resolved Electrostatic Force Microscopy.
Imaging Charge Transfer State Excitations in Polymer/Fullerene Solar Cells with Time-Resolved Electrostatic Force Microscopy.
复制标题
使用时间分辨静电力显微镜对聚合物/富勒烯太阳能电池中的电荷转移态激发进行成像。
DOI：
10.1021/acs.jpclett.5b01360
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
D. Ginger
中科院分区：
文献类型：
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作者：
Phillip A. Cox;Micah S. Glaz;Jeffrey S. Harrison;Samuel R. Peurifoy;D. Coffey;D. Ginger
我们用时间分辨静电力显微镜(TrEFM)演示了聚合物/富勒烯体相异质结太阳能电池中电荷转移态光激发的纳米尺度成像。我们比较了模型体系poly[2-methoxy-5-(3‘，7’-dimethyloctyloxy)-1，4-phenylenevinylene]和[6，6]-苯基C61丁酸甲酯在能隙上和能隙下激发的局域trEFM充电率和外量子效率。结果表明，对于能隙以上和能隙以下的光激发，局域trEFM充电率与器件EQE相关，表明EFM方法具有足够的灵敏度来检测与CT态形成相关的低EQE，这一结果对于探测量子点和有机金属卤化物钙钛矿太阳能电池等纳米材料中的弱亚能隙激发是有用的。进一步，我们用trEFM映射了有机光伏(OPV)中子能隙CT激发产生的EQE的空间变化，发现这些态产生的光电流的局域分布与带隙以上单重态激发产生的EQE的空间变化几乎是相同的。这些结果与最近的工作一致，表明能隙上和能隙下的激发具有相似的内部量子效率。
We demonstrate nanoscale imaging of charge transfer state photoexcitations in polymer/fullerene bulk heterojunction solar cells using time-resolved electrostatic force microscopy (trEFM). We compare local trEFM charging rates and external quantum efficiencies (EQE) for both above-gap and below-gap excitation of the model system poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM). We show that the local trEFM charging rate correlates with device EQE for both above-gap and below-gap photoexcitation, demonstrating that EFM methods have sufficient sensitivity to detect the low EQEs associated with CT state formation, a result that could be useful for probing weak subgap excitations in nanostructured materials such as quantum dot and organometal halide perovskite solar cells. Further, we use trEFM to map spatial variations in EQE arising from subgap CT excitation in organic photovoltaics (OPVs) and find that the local distribution of photocurrent arising from these states is nearly identical to the spatial variation in EQE from above-gap singlet excitation. These results are consistent with recent work showing that both above-gap and below-gap excitation have similar internal quantum efficiency.