激基复合物给体作间隔层对激子复合区域的调节

为研究激基复合物器件激子复合区域的变化,在TPD/BPhen界面可形成激基复合物发光的基础上,以Ir(pq)2(acac)为探测层,制备器件ITO/Mo O_3(2.5 nm)/TPD((40-x)nm)/Ir(pq)2(acac)(0.5 nm)/TPD(x,x=0,3,6,10 nm)/BPhen(40 nm)/Cs2CO_3/Al,其中靠近BPhen的TPD称之为间隔层。电致发光光谱表明,该组器件的激子复合区域主要位于Ir(pq)2(acac)薄层和TPD/BPhen界面,分别发射595 nm和478 nm的光。随着TPD间隔层厚度的增加和电压的升高,发光区域向激基复合物区域(TPD/BPhen界面)移动,即更多的电子和空穴在TPD/BPhen界面形成激基复合物发光,Ir(pq)2(acac)发光减弱。当间隔层厚度由0 nm增至10nm时,6 V电压下的Ir(pq)2(acac)和激基复合物发光强度的比值由44降至1.5。对于间隔层厚度为6 nm的器件,Ir(pq)2(acac)和激基复合物发光强度的比值由6 V时的2.8降至10 V时的1.0。由此可见,激基复合物给体作间隔层能有效调节激子复合区域。

Adjustment of Exciton Recombination Zone by Utilizing The Donor of Exciplex as Spacer Layer

In order to adjust the exciton recombination zone of exciplex-based organic light-emitting diodes, four devices were fabricated by employing Ir(pq)2(acac) as a prober and utilizing the donor of exciplex as a spacer.The device structures are ITO/MoO3(2.5 nm)/TPD((40-x) nm)/Ir(pq)2(acac)(0.5 nm)/TPD(x, x=0, 3, 6, 10 nm)/BPhen(40 nm)/Cs2CO3/Al, where x is the thickness of the spacer layer and the TPD/BPhen interface produces the exciplex emission.The electroluminescent spectra of the four devices include two main peaks: 478 nm and 595 nm, which originate from the TPD/BPhen interface and Ir(pq)2(acac) layer , respectively.As both the thickness of TPD spacer and the applied voltage increase, the recombination zone shifts towards TPD/BPhen interface.That is, more electrons and holes recombine at the interface between TPD and BPhen, leading to the decreased intensity of Ir(pq)2(acac) emission.For instance, under an applied voltage of 6 V, the intensity ratio of emission from Ir(pq)2(acac) and exciplex (IIr complex∶Iexciplex) is 44.0 and 1.5 for the devices with 0 and 10 nm spacer, respectively.The value of IIr complex∶ Iexciplex decreases from 2.8 at 6 V to 1.0 at 10 V for the device with 6-nm-thick TPD spacer.Therefore, the recombination region can be effectively tuned by utilizing the donor of exciplex as a spacer.