Charge transport perpendicular to the high mobility plane in organic crystals: Bandlike temperature dependence maintained despite hundredfold anisotropy
Charge transport perpendicular to the high mobility plane in organic crystals: Bandlike temperature dependence maintained despite hundredfold anisotropy
复制标题
有机晶体中垂直于高迁移率平面的电荷传输：尽管具有数百倍的各向异性，但仍保持带状温度依赖性
DOI：
10.1103/physrevb.93.035205
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发表时间：
2016
影响因子：
3.7
通讯作者：
Blülle B
中科院分区：
文献类型：
--
作者：
Blülle B
货车德瓦尔斯键合有机晶体中的载流子迁移率强烈依赖于相邻分子之间的转移积分，因此电荷输运的各向异性由晶格内的分子排列决定。在这里，我们报告的温度依赖于运输测量沿着所有三个主要的晶体方向相同的红荧烯单晶的高纯度。空穴迁移率是由垂直于分子层的高频导纳谱测量的载流子渡越时间和两个场效应晶体管（FET）结构在层中相互垂直的传输特性得到的。虽然场效应通道的测量证实了先前报道的高迁移率和平面内的各向异性，但我们发现在相同晶体中垂直于分子层的迁移率要低约两个数量级。虽然带宽是消失的小沿着的方向和运输不能连贯，我们发现增加后冷却。我们表明，在高mobilityplane的离域防止小极化子的形成，并导致观察到的“带状”温度依赖性也在垂直于分子层的方向，尽管不相干的传输机制。
Charge carrier mobility in van der Waals bonded organic crystals is strongly dependent on the transfer integral between neighboring molecules, and therefore the anisotropy of charge transport is determined by the molecular arrangement within the crystal lattice. Here we report on temperature dependent transport measurements along all three principal crystal directions of the same rubrene single crystals of high purity. Hole mobilities are obtained from the carrier transit time measured with high-frequency admittance spectroscopy perpendicular to the molecular layersand from the transfer characteristics of two field-effect transistor (FET) structures oriented perpendicularly to each other in the layersand. While the measurements of the field-effect channels confirm the previously reported high mobility and anisotropy within theplane, we find the mobility perpendicular to the molecular layers in the same crystals to be lower by about two orders of magnitudeat. Although the bandwidth is vanishingly small along thedirection and the transport cannot be coherent, we findto increase upon cooling. We show that the delocalization within the high mobilityplane prevents the formation of small polarons and leads to the observed “bandlike” temperature dependence also in the direction perpendicular to the molecular layers, despite the incoherent transport mechanism.