Study On A Single-layered Multi-components OPC By Using Diphenoquinone Derivatives As ETM

Organic photoconductive materials have become one of the high-techmaterials that are indispensable in the modern information society and foundwide applications in the areas such as IT, office automation, printing and etc.At the same time, due to its attractive and promising future and numerousmarket potentials, organic photoconductive materials and devices haveincreasingly caused attention and interests among scientists and technologists.With the growingly expanded use and rapid development of organicphotoconductor, environment friendly organic photoconductive materials witheven higher response speed, sensitivity and low cost are widely demanded.Currently, the most widely used organic photoconductors are unexceptionallyminus charging multi-layered ones and are suffering from complicatedmanufacturing processes and high cost. Minus charging may, at the same time,cause contaminations to the working environment. From the viewpoint ofenvironmental protection and industrial application, the development ofsingle-layered photoreceptor capable of plus- and minus-charging (bipolarityOPC) is of great significances. .Based on the previous studies, we synthesized a series of noveldiphenoquione ETMs and applied them to the single-layered multi-componentsphotoreceptor. Systematic investigation was carried out on fundamentalproperties of the ETMs and applied performances of the photoreceptor. Highperformance photoreceptors of positive charging and bipolarity charging weresuccessfully developed by changing the materials,formula and devicestructure. Studies were also done on the photoconducting mechanism andperformances of the single-layered photoreceptor. In brief, the main contentsof this work are described as follows:1. On basis of the previous studies, we optimized and produced the smallmolecular diphenoquione derivatives of excellent performances (noted asETM1,ETM2 and ETM3). Comprehensive measures and evaluations weredone on basic physical characteristics and device performances of these threenewly prepared ETMs. Experimental results showed that these threecompounds had good solubility in common organic solvents and excellentcompatibility with polymers. These compounds could be doped in polymerslike PC and Vylon200 at concentrations over 40wt% and were, therefore,favorable in making heavily doped photoreceptors. In addition, they werestable and less toxic. ETM2 was found the best in every investigatedperformances among the other ETMs when doped together with HTM andCGM in polymer matrix. When exposed at 780nm, photoreceptors doped with20% ETM2 was bipolarity chargable and showed better performances thanthose doped with TNF. And the half decay exposures for positive and negativecharging were 2.2μJ/cm2 and 2.8μJ/cm2, respectively.2. Upon investigating the relationship between ETM concentration andOPC performances, we found that photosensitivity of single-layeredthree-components photoreceptor was strongly dependent on ETMconcentration. Half decay exposure decreased with increasing ETMconcentration and reached a minimum at 10%, and then slightly increased ateven higher concentrations. The sensitivity was found an increasing functionwith increasing HTM concentration and reached maximum When HTMconcentration was at 35%. Through materialsˊ matching, an optimal formulawas found for the single-layered three components OPC as follows (in weightparts): ETM2/DEH/H2Pc/PC=10:35:1.2:100.3.Through increasing the concentration of CGM, we got a highly sensitivesingle-layered two-components photoreceptor. The experimental resultsindicated that photosensitivity of the photoreceptor increased with increasingCGM concentration and tended to be saturated when CGM concentration wasover 15%. At such high concentrations, incident photons were completelyabsorbed at the surface of photoreceptor within 1 μm and charge generationwas, therefore, localized in the surface of phtoreceptor. And the bulk ofphotoreceptor acted only as the space for charge of single polarity totransport(electron or hole, according to the type of transport material andcharging polarity employed). That is to say, a single-layered photoreceptor withseparated functions was obtained. In this strategy, photoreceptor withECH:H2Pc:PC=45:15:100 (in weight parts) was found the best as positivelychargable single-layered photoreceptor and the half decay exposure was keptin sub-microjoule levels around 0.59μJ/cm2.4.In order to investigate photoconducting mechanism of the single-layeredphotoreceptor, we designed and prepared duo-layered photoreceptors witheither ETM- and HTM-doped charge transport layer or transportmaterial-permeated charge generation layer, and measured and evaluatedtheir xerographic properties. It was found that the coexistence of ETM andHTM in the transport layer did not equally promote electron and hole transportproperties and could not reach the goal of bipolarity charging. In the transportmaterial-permeated photoreceptor, the existence of ETM in CTL did promotethe positive charging properties, but the device sensitivity still remained at avery low level.