Hole-transport Materials Based On 1-substituted Carbazole And Its Application In Organic Electronic Devices

Organic semiconductors are limited by low carrier mobility,and their devices are usually based on organic functional films with a thickness of tens to hundreds of nanometers.The contact characteristics of the organic semiconductor interface often determine the performance of the device,rather than the bulk characteristics of the material.For example,organic electroluminescent diode devices(OLED),organic solar cells(OPV),and organic photodiodes(OPD)use a conductor/organic functional layer/conductor sandwich device structure,through the metal-semiconductor contact interface and organic heterojunctions.The heterojunction interface realizes important functions such as rectification and photoelectric conversion.Because it is difficult for a single material to meet the needs of carrier transport and photoelectric conversion at the same time,researchers have developed devices with multi-functional layers.These functional layers each perform their duties to jointly construct high-performance devices.However,the multilayer device structure also brings processing,compatibility,and cost issues.Especially in solution processing devices,the problem of mutual solubility may occur during the processing of the multifunctional layer.For example,in a front-mounted device,the hole interface layer near the bottom anode is processed first and is corroded by the subsequent processing solution.From the perspective of material design,this paper designs and synthesizes a series of new small molecule hole transport materials and polymer hole transport materials based on the interlayer miscibility problems encountered by the current solution-processed organic photoelectric devices Study and characterize the photoelectric properties and device performance.The main contents are as follows.Hole-transport materials HT2 and HT3 based on 1-carbazole cell were designed and synthesized.The films have good anti-solvent properties after being cross-linked at 210 ^oC,which can be used to modify PEDOT:PSS layer in organic light detectors.A hole transporting material HT2 or HT3 with appropriate energy levels and electron blocking ability is inserted between PEDOT:PSS and the active layer,which can not only effectively block electrons from entering the hole transport layer,but also prevent acid PEDOT:PSS from attacking the active layer material.Among them,the specific detection rate of OPD device prepared by using HT3 as hole transport layer solution method can reach 2.65×10¹³ Jones,which is significantly improved compared with the device without hole transport layer.In order to further reduce the cross-linking temperature,we designed and synthesized a styrene-based cross-linkable hole transport material HT6 with triphenylamine as the core side chain and 1-carbazole,which can not only achieve complete cross-linking of the material at160 ^oC but has very good resistance to solvent erosion and can effectively improve the device performance of organic light-emitting diodes,obtaining high color purity blue polymer light-emitting diodes with a current efficiency of 3.50 cd/A at a brightness of 1000 cd/m².We also designed and synthesized a polymer hole transport material p-HT4 with a non-conjugated backbone,which has good compatibility with the traditional hole transport material PVK.p-HT4 is polymerized by ethylene double bond under AIBN catalysis.Through electrochemical test,it has a highest occupied molecular orbtal energy level of-5.6 e V,which is well matched with PVK and luminescent materials.By optimizing the blending ratio of PVK:p-HT4,a high color purity blue polymer light-emitting diode with a current efficiency of4.13 cd/A at brightness of 1000 cd/m² was realized,compared to a light-emitting device containing only PVK as a hole transport layer Performance has improved significantly.These results indicate that by selecting suitable hole transport materials,simple and effective hole transport materials can be obtained through simple physical blending,which provides a new idea for the preparation of high-efficiency and stable blue polymer light-emitting diodes.