Many studies have analyzed the mobility and injection characteristics of charge carriers for organic light-emitting diodes (OLEDs) using hole-only and electron-only devices (HODs and EODs). However, the charge dynamics of a single type of carrier cannot fully represent the characteristics of light-emitting devices such as charge balance, recombination, and efficiency. In this report, we applied the impedance spectroscopy (IS) measurement to operating devices with light-emission. A series of thermally activated delayed fluorescence (TADF) OLEDs with a single or mixed host were fabricated and their electro-optical properties were comprehensively investigated. 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl (CBP) and 2,2′,2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) were used for the single host and a mixture of CBP and TPBi (1:1 ratio) was used for the mixed host; 2,4,5,6-Tetra(9H-carbazol-9-yl) isophthalonitrile (4CzIPN) was used as an emitter. In all the OLEDs, the injection and transporting property of holes and electrons were successfully discriminated from the Bode plots of the modulus. Besides, the recombination properties depending on the type of hosts were also thoroughly understood from capacitance (C)-voltage (V), Re(z)-frequency and Cole-Cole plots. The modulus Bode plot revealed that the voltage of the maximum efficiency coincided with the voltage at which the low frequency (electron) signal merges with the high frequency (hole) signal in the mixed host system.

许多研究已经分析了仅使用空穴和仅使用电子的器件（HOD和EOD）的有机发光二极管（OLED）电荷载流子的迁移率和注入特性。但是，单一类型载流子的电荷动力学不能完全代表发光器件的特性，例如电荷平衡，重组和效率。在本报告中，我们将阻抗光谱（IS）测量应用于发光设备。制备了一系列具有单个或混合主体的热活化延迟荧光（TADF）OLED，并对其电光性能进行了全面研究。4,4'-双（N-咔唑基）-1,1'-联苯（CBP）和2,2'，2“-（1,3,5-苯甲三基）-三（1-苯基-1-H-苯并咪唑（TPBi）用于单一宿主以及CBP和TPBi（1：1个比例）用于混合宿主；2,4,5,6-四（9H-咔唑-9-基）间苯二甲腈（4CzIPN）被用作发射极。在所有的OLED中，空穴和电子的注入和传输性质都已成功地从模量的伯德图上区分出来。此外，还可以从电容上彻底了解取决于宿主类型的重组特性（C）-电压（V），Re（z）-频率和Cole-Cole图。模量波特图显示，在混合主机系统中，最大效率的电压与低频（电子）信号与高频（空穴）信号合并的电压一致。