Organic semiconductor spintronics: utilizing triplet excitons in organic electronics.
Organic semiconductor spintronics: utilizing triplet excitons in organic electronics.
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有机半导体自旋电子学：在有机电子学中利用三线态激子。
DOI：
10.1098/rsta.2015.0121
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Monkman A
中科院分区：
文献类型：
--
作者：
Monkman A
有机电子现在支持一个快速增长的行业，包括用于手机显示器和高档电视的有机发光二极管（OLED）显示器。这已经通过材料和设备的成功工程实现，并且还通过允许控制电子自旋的新设备架构的设计实现。这是一个快速发展的领域，基础半导体科学的一些最新进展可能会使新的应用成为可能。这个问题将集中在束缚电子空穴对（激子）的自旋状态的作用，这些电子空穴对在LED中提供光发射或在太阳能电池中分离以提供自由电荷。在这些激子中涉及的两个电子的自旋可以被排列为零自旋“单线态”或自旋-1“三线态”，并且对于大多数有机半导体，自旋交换能使单线态显著高于三线态，通常为0.5eV。对于简单的OLED，只有25%的电子-空穴复合事件可以形成自旋单线态激子，然后可以发射光子，而剩余的75%形成非发射三重态激子。这是对LED效率的严重限制，并且开发了许多方法来避免这种限制。首先，事实证明，三重态激子之间的碰撞可以导致它们的“融合”以形成发射性自旋单重态激子，并且在某些条件下，这可以是三重态激子的主要衰变通道。这能在多大程度上提高效率仍然是一个活跃的研究问题。第二，如果可以引入强的自旋-轨道耦合，则可以实现来自三重态激子的直接发射（磷光）。已经发现含有铱、铂和锇的有机化合物是有效的，特别是对于红色和绿色发射。第三，最近在分子半导体的设计方面取得了很大进展，
Organic electronics now supports a rapidly growing industry, including organic light-emitting diode (OLED) displays as used in cell phone displays and upmarket TVs. This has been enabled both by successful engineering of materials and devices, and also through the design of new device architectures that allow control of electron spin. This is a rapidly moving field, and some recent advances in the basic semiconductor science are likely to enable new applications. This issue will focus on the role of the spin state of the bound electron-hole pairs (excitons) that provide light emission in LEDs or separate to give free charge in solar cells. The spins of the two electrons involved in these excitons can be arranged as zero-spin ‘singlet’states or spin-1 ‘triplet’states, and for most organic semiconductors the spin exchange energy raises the singlet state substantially above the triplet, typically by 0.5 eV.For simple OLEDs, only 25% of the electron-hole recombination events can form spin singlet excitons that can then emit photons, with the remaining 75% forming non-emissive triplet excitons. This is a severe limitation to LED efficiency and a number of approaches are developed to avoid this limitation. First, it turns out that collisions between triplet excitons can result in their ‘fusion’to form an emissive spin singlet exciton, and under some conditions this can be the dominant decay channel for triplet excitons. How much this can raise efficiency remains an active research question. Second, direct emission from the triplet exciton (phosphorescence) can be achieved if strong spin–orbit coupling can be introduced. Organometallic compounds containing iridium, platinum and osmium have been found effective, particularly for red and green emission. Third, there has been very recent progress in the design of molecular semiconductors with very