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Charge transfer excitons in a donor–acceptor amphidynamic crystal: the role of dipole orientational order
Materials Horizons ( IF 12.2 ) Pub Date : 2020-08-25 , DOI: 10.1039/d0mh01044h Joshua W. R. Macdonald 1, 2, 3, 4, 5 , Giacomo Piana 5, 6, 7, 8, 9 , Massimiliano Comin 10, 11, 12 , Elizabeth von Hauff 13, 14, 15, 16 , Gabriele Kociok-Köhn 4, 5, 17, 18 , Chris Bowen 4, 5, 18, 19 , Pavlos Lagoudakis 5, 6, 7, 8, 9 , Gabriele D'Avino 10, 11, 12 , Enrico Da Como 1, 2, 3, 4, 5
Materials Horizons ( IF 12.2 ) Pub Date : 2020-08-25 , DOI: 10.1039/d0mh01044h Joshua W. R. Macdonald 1, 2, 3, 4, 5 , Giacomo Piana 5, 6, 7, 8, 9 , Massimiliano Comin 10, 11, 12 , Elizabeth von Hauff 13, 14, 15, 16 , Gabriele Kociok-Köhn 4, 5, 17, 18 , Chris Bowen 4, 5, 18, 19 , Pavlos Lagoudakis 5, 6, 7, 8, 9 , Gabriele D'Avino 10, 11, 12 , Enrico Da Como 1, 2, 3, 4, 5
Affiliation
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Large amplitude motions in molecular solids are responsible for anomalous electrical characteristics in amphidynamic crystals. We study the effect of orientational dipolar disorder on charge transfer excitons (CTEs) in a donor–acceptor amphidynamic co-crystal of perylene–tetrabromophthalic anhydride (–TBPA). This co-crystal offers long range positional order of alternating donor and acceptor molecular entities arranged in stacks. Further it has a phase transition at 250 K due to progressive freezing of the dipolar orientational motion in the TBPA permanent dipole. The optical absorption band and photoluminescence at the semiconductor gap consists of at least three energetically separated CTE resonances that cover a spectral range of more than 400 meV. As the temperature is lowered below the phase transition the CTE band remains broad, but shows a shift of ∼150 meV to higher energy. On the basis of optical reflectivity, photoluminescence, and model calculations we interpret the room temperature CTE band as a collection of resonances in which at least one the nearest neighbour dipoles to the CTE is flipped from their lowest energy configuration. This first comprehensive optical investigation on an amphidynamic co-crystal demonstrates the importance of understanding the role of permanent dipoles in the CTE photophysics of organic semiconductors.
中文翻译：
供体-受体两性动力学晶体中的电荷转移激子：偶极取向顺序的作用
分子固体中的大振幅运动是造成两性晶体中异常电学特性的原因。我们研究了di-四溴邻苯二甲酸酐（-TBPA）供体-受体两性共晶中电荷转移激子（CTE）定向偶极障碍的影响。这种共晶体提供了交替排列的供体和受体分子实体的远距离位置顺序。此外，由于在TBPA永久偶极子中偶极子定向运动的逐渐冻结，它在250 K处具有相变。半导体间隙处的光吸收带和光致发光由至少三个能量分离的CTE共振组成，其覆盖的光谱范围超过400 meV。当温度降低到相变以下时，CTE谱带仍然很宽，但显示出〜150 meV向更高的能量偏移。根据光反射率，光致发光和模型计算，我们将室温CTE波段解释为一组共振，其中至少一个最接近CTE的偶极子从其最低能量构型翻转过来。首次对两性动力学共晶体进行了全面的光学研究，证明了理解永久偶极子在有机半导体CTE光物理中的作用的重要性。
更新日期：2020-09-01
中文翻译：
供体-受体两性动力学晶体中的电荷转移激子：偶极取向顺序的作用
分子固体中的大振幅运动是造成两性晶体中异常电学特性的原因。我们研究了di-四溴邻苯二甲酸酐（-TBPA）供体-受体两性共晶中电荷转移激子（CTE）定向偶极障碍的影响。这种共晶体提供了交替排列的供体和受体分子实体的远距离位置顺序。此外，由于在TBPA永久偶极子中偶极子定向运动的逐渐冻结，它在250 K处具有相变。半导体间隙处的光吸收带和光致发光由至少三个能量分离的CTE共振组成，其覆盖的光谱范围超过400 meV。当温度降低到相变以下时，CTE谱带仍然很宽，但显示出〜150 meV向更高的能量偏移。根据光反射率，光致发光和模型计算，我们将室温CTE波段解释为一组共振，其中至少一个最接近CTE的偶极子从其最低能量构型翻转过来。首次对两性动力学共晶体进行了全面的光学研究，证明了理解永久偶极子在有机半导体CTE光物理中的作用的重要性。
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