Light-emitting electrochemical cells (LECs) are one of the simplest electroluminescent devices and consist of a single emissive organic/salt layer sandwiched between two electrodes. The unique attribute of an operated LEC is the development of a p-doped/intrinsic/n-doped (p–i–n) structure in the active layer in which the doped regions allow for facile transport of electronic charges to the intrinsic region, where charge recombination and light emission occur. However, due to the complex and simultaneous motion of ionic and electronic charges, the examination of the p–i–n structure and the zone where the light is emitted (EZ) is challenging during operation. By analyzing incident photon-to-current conversion efficiency and angular emission measurements with optical simulations, and correlating the results with capacitance measurements, we are able to obtain a clear picture of the p–i–n situation and the EZ within the active layer of a sandwich-type LEC during operation. It is found that the p-doped zone grows to the center of the active layer while the EZ stays closer to the metal electrode and is unchanged over time. Furthermore, optical simulations reveal that the determined EZ limits the external quantum efficiency of the LEC by outcoupling efficiencies of less than 10%.

中文翻译：

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三明治型发光电化学电池中随时间变化的p–i–n结构和发射区

发光电化学电池（LEC）是最简单的电致发光器件之一，由夹在两个电极之间的单个发光有机/盐层组成。被操作的LEC的独特属性是在有源层中形成了p掺杂/本征/ n掺杂（p–i–n）结构，其中掺杂区允许将电荷方便地传输到本征区，发生电荷复合和发光的地方。但是，由于离子电荷和电子电荷的复杂且同时的运动，在操作过程中检查p–i–n结构和发射光的区域（EZ）颇具挑战性。通过使用光学模拟分析入射光子到电流的转换效率和角发射测量值，并将结果与​​电容测量值相关联，在运行期间，我们能够清晰地了解p–i–n情况和三明治型LEC有源层内的EZ。已经发现，p掺杂区生长到有源层的中心，而EZ保持更靠近金属电极，并且随时间保持不变。此外，光学模拟表明，确定的EZ通过小于10％的耦合效率限制了LEC的外部量子效率。