基于TPD:PO-T2T的黄光激基复合物发光性能研究

Investigation of luminescent properties based on TPD:PO-T2T yellow exciplex

通过多源有机分子气相沉积系统(LN-386SA)制备结构为ITO/HAT-CN/TPD/TPD:PO-T2T/PO-T2T(x=10,20,30,40,50,60,70 nm)/LiF/Al的有机发光器件,研究了电子传输层(PO-T2T)厚度对TPD:PO-T2T黄光激基复合物发光性能的影响。PO-T2T厚度对其电致发光(electroluminescence,EL)光谱几乎没有影响,但对电流密度(current density,CD)、亮度、效率等性能有较大影响。由于金属铝扩散至发光层中会形成淬灭中心降低发光效率,当PO-T2T越厚时,扩散至发光层的铝原子越少,因此发光效率随PO-T2T厚度增加而增加。当PO-T2T厚度为70 nm时,获得最大电流效率(current efficiency,CE)和功率效率(power efficiency,PE),分别为2.16 cd/A、2.12 lm/W。此外,瞬态EL性能表明TPD:PO-T2T的发光来自TPD和PO-T2T分别对载流子的直接捕获,没有发光瞬时过冲或者深陷阱中载流子逃逸复合发光的现象。

To investigate the effect of the thickness of electron transport layer(PO-T2T)on the luminescent properties of TPD:PO-T2T yellow exciplex,the devices with a structure of ITO/HAT-CN/TPD/TPD:PO-T2T/PO-T2T(x=10,20,30,40,50,60,70 nm)/LiF/Al are fabricated by multi-source organic molecular vapor deposition system(LN-386SA).The electroluminescent(EL)spectra of the devices are barely changed by the thickness of PO-T2T,while other properties such as current density(CD),luminance as well as efficiencies are greatly changed.The luminescent efficiencies are increased with the increase of PO-T2T thickness,which is mainly attributed to the reduction of quenching center in the emissive layer caused by the diffusion of aluminum cathode.When the thickness of PO-T2T is 70 nm,the maximums of current efficiency(CE)and power efficiency(PE)are 2.16 cd/A and 2.12 lm/W,respectively.In addition,transient overshoot and recombination of carriers captured by deep traps are not observed through the transient EL properties of the devices,which indicates that the emission of the TPD:PO-T2T exciplex are originated from the direct carrier recombination.