Hole versus electron transport in fullerenes
Hole versus electron transport in fullerenes
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DOI：
10.1016/j.orgel.2023.106798
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发表时间：
2023-03
影响因子：
3.2
通讯作者：
Eunkyung Cho;V. Coropceanu;J. Brédas
中科院分区：
文献类型：
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作者：
Eunkyung Cho;V. Coropceanu;J. Brédas
通过密度泛函理论（DFT）计算得到了描述C60和C70及其衍生物的空穴和电子输运性质的微观参数。计算的弛豫能和简正模分析的结果指出，有没有显着的差异之间的电子-振动耦合和空穴-振动耦合在C60系统，其中空穴和电子转移的重组能量之间的差异不超过10 meV，除了在母C60系统的情况下，这一差异是约40 meV。C60及其衍生物中空穴和电子的电子耦合的DFT估计也被发现是非常相似的。因此，我们的理论结果证实了最近的实验研究的结论，强调C60富勒烯不应该被视为只是n型传输材料，但实际上是固有的双极性。对C70进行的DFT计算表明，空穴传输的重组能量略低于（5毫电子伏）比电子传输，这种差异甚至更大，高达100毫电子伏，在功能化的C70系统。这些结果表明，在C70及其衍生物的空穴迁移率也可以与相应的电子迁移率相当，甚至更大。此外，DFT计算表明，对于未取代富勒烯，衍生化对电离势能的影响远大于对电子亲和能的影响，两者均降低;因此，可以进一步利用化学改性来降低C60和C70的固有高IP值，并导致与普通电极的功函数更好地匹配，这将有助于空穴注入。
We have carried out density functional theory (DFT) calculations to derive the microscopic parameters that describe the hole and electron transport properties in C60and C70and their derivatives. The computed relaxation energies and the results of normal-mode analyses point out that there are no significant differences between the electron-vibration couplings and hole-vibration couplings in the C60systems, where the differences between the reorganization energies for hole and electron transfers do not exceed 10 meV, except in the case of the parent C60system where this difference is about 40 meV. The DFT estimates of the electronic couplings for holes and electrons in C60and its derivatives are also found to be very similar. Thus, our theoretical results confirm the conclusions of recent experimental investigations that underline that the C60fullerenes should not be regarded as just n-type transporting materials but in fact are intrinsically ambipolar. The DFT calculations performed for C70show that the reorganization energy for hole transport is slightly lower (5 meV) than for electron transport and this difference is even larger, up to 100 meV, in the functionalized C70systems. These results suggest that hole mobilities in C70and its derivatives could also be comparable or even larger than the corresponding electron mobilities. In addition, the DFT calculations indicate that, with respect to unsubstituted fullerenes, the derivatization has a much larger impact on the ionization potential energies than on the electron affinity energies, which are both reduces; therefore, chemical modifications could be further exploited to decrease the intrinsically high IP values of C60and C70and lead to a better match with the workfunctions of common electrodes, which would facilitate hole injection.