| Organic lighting-emitting devices are electrical driven devices which contain organic materials as emitting media.OLEDs have attracted great attentions in modern science and technology owing to their attractive characteristics of small volume,light weight,large viewing angle,high resolution and flexibility,etc.And it has good prospects for application in flat panel displays.Organic Lighting-Emitting devices are charge type devices,thus carrier-injecting from the electrode to emitting layer is crucial to the performance of OLEDs.Hole-injecting layers are very important components in high-performance OLEDs.Modification of hole-injecting layer is an important means to improve the performance of OLEDs.Graphene oxide has a better solution-processable due to oxygen functional groups on GO surface.And band gap of graphene oxide depends on degree of oxidation,therefore it shows great potentials for use in optoelectronic devices.Here we present an investigation of organic electroluminescent devices with a solution-processable graphene oxide as HTL.We have concerned on the functionalized modification of graphene oxide to improve electroluminescent properties of organic light-emitting devices.In first part of this paper,we have explored suitable condition for graphene oxide hole-injecting material with Alq3 as emitting media.It contains an optimum thickness,optimal degrees of oxidation and best matching hole-transporting layer.Adjusting GO concentration and additional repetitions of spin-coating led to desired full coverage of GO films.OLEDs with optimum thickness GO interlayer show maximum luminance of 6606 cd/m2,maximum luminous efficiency of 2.85 cd/A.Then we adjusted oxidation degrees of graphite oxide via ultraviolet reduction.OLEDs based on optimal oxidation degrees of graphite oxide show maximum luminance of 8470 cd/m2and maximum luminous efficiency of 4.79 cd/A,which corresponds to great enhancement compared to that of original GO-based OLEDs.We used TPD and NPB as the hole transport layer of OLEDs.The results show that the electroluminescent properties of OLEDs which used NPB as HTL are all better than that of TPD-based OLEDs.The maximum luminance of 11170 cd/m2 enhanced by 50%that of TPD-based OLEDs,and the maximum luminous efficiency of 8.09 cd/A increased by98%comparing to that of TPD-based OLEDs.In second part of this paper,basing on the optimal device configuration of first part,we have explored the effect of reduced graphene oxide doping by conjugated ionic compounds on its hole injecting ability.Conjugated ionic compounds modified reduced graphene oxide byπ-πstacking.The results show that rGO doping by conjugated ionic compounds can improve the electroluminescent properties of OLEDs.OLEDs which used rGO doping by 10wt%N,N-dimethyl-9,9’-biacridinium dinitrate as HIL show maximum luminance of 7759 cd/m2,maximum luminous efficiency of 5.37 cd/A.The device performance is increased with the 10,10’-dimethyl-9,9’-biacridinum bis（monomethyl terephthalate）increased to the optimum weight of 4wt%.At the optimal doping ratio of 4wt%,the maximum luminance of the device is 19950 cd/m2,which corresponds to a 120%enhancement comparing to that of the pure rGO HIL-based OLED.And he maximum luminous efficiency of the device is 15.46 cd/A,which corresponds to a 250%enhancement in efficiency comparing to that of the pure rGO HIL-based OLED.In third part of this paper,we used perovskite compounds CH3NH3PbBr3 instead of small fluorescent molecule Alq3.The stability of perovskite thin film in the air is enhanced by adding 1,8-diaminooctane bromate in the perovskite precursor.The fluorescence intensity is much higher than that of the undoped film,and the fluorescence intensity is highest when the molar ratio between CH3NH2Br and 1,8-diaminooctane bromate is 50:50.Then we fabricated perovskite light-emitting devices with rGO doping by conjugated ionic compounds as HIL in air,and the maximum luminance of the device is 185 cd/m2. |
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