Molecular packing-dependent photoconductivity in functionalized anthradithiophene crystals
Molecular packing-dependent photoconductivity in functionalized anthradithiophene crystals
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DOI：
10.1016/j.orgel.2018.12.040
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发表时间：
2019-04
影响因子：
3.2
通讯作者：
Keshab Raj Paudel;G. Giesbers;J. Schenck;J. Anthony;O. Ostroverkhova
中科院分区：
文献类型：
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作者：
Keshab Raj Paudel;G. Giesbers;J. Schenck;J. Anthony;O. Ostroverkhova
本文将时间分辨光电流中观察到的特征与两种不同填充基序的反噻吩（ADT）衍生物diF TES-ADT和diF TSBS-ADT晶体的结构和无序性联系起来。与具有一维“三明治-人字形”填料的diF TSBS-ADT相比，具有二维“砖砌”填料的diF TES-ADT晶体获得了高10-12倍的峰值光电流，这主要是由于固有电荷载流子迁移率的差异。在230-300 K（200-300 K）下，零电场活化能为~ 40-50 meV的TES （TSBS）导数从浅阱介导的热激活状态转变为较低温度下的温度无关行为。浅层圈闭归因于结构缺陷，例如，与TES导数中的固-固相变有关。在diF TES-ADT中，在所有温度（80 - 300 K）下，大多数电荷在<0.4 ns时间尺度上捕获，在300 K下在0.4 - 10 ns时间尺度上移动的载流子在80 K下仍保持移动。相比之下，diF TSBS-ADT晶体中的浅俘获在纳秒时间尺度上进行，在低温下明显失去了移动载流子。随后在更长的时间尺度上进行深捕获，这导致在连续波激发下在diF TSBS-ADT晶体中获得的稳态光电流比diF TES-ADT低约250倍。
We relate features observed in time-resolved photocurrent with crystal structure and disorder in crystals of two anthradithiophene (ADT) derivatives with different packing motifs, diF TES-ADT and diF TSBS-ADT.A factor of ∼10–12 higher peak photocurrent was obtained in the diF TES-ADT crystals characterized by a 2D “brickwork” packing as compared to diF TSBS-ADT with a 1D “sandwich-herringbone” packing, primarily due to differences in intrinsic charge carrier mobility. A change from shallow trap-mediated thermally activated regime at 230–300 K (200–300 K), with a zero-electric field activation energy of ∼40–50 meV, in the TES (TSBS) derivative to the temperature independent behavior at lower temperatures in both derivatives was observed. The shallow traps were attributed to structural defects associated, for example, with a solid-solid phase transition in the TES derivative. In diF TES-ADT, most charge trapping in shallow traps occurred on <0.4 ns time scales at all temperatures (80–300 K) and the carriers that were mobile at 0.4–10 ns time scales at 300 K remained mobile at 80 K. In contrast, shallow trapping in the diF TSBS-ADT crystals proceeded on the nanosecond time scales, with a pronounced loss of mobile carriers at low temperatures. This was followed by deep trapping at longer time scales, which led to a factor of ∼250 lower steady-state photocurrent obtained under continuous wave excitation in the diF TSBS-ADT crystals as compared to diF TES-ADT.