Investigation On Structure Design And Field Luminescence Enhancement Of Quantum Dot Light-Emitting Field Effect Transistor

In recent years,quantum dot light-emitting field-effect transistor(QLET)can integrate the excellent gate-regulation of carriers by field-effect transistor(FET)and the high device efficiency,narrow emission wavelength and wide spectrum of the colloidal quantum dot light-emitting diode(QLED).Because of these advantages,QLET has attracted a great deal of research and attention.The integration of high-efficiency luminescence and luminance regulation by exploiting the field effect is the key to the frontier of QLET research and application.However,how to maximize the field effect based on the design of the device structure and the optimization of the gate form to precisely regulate the carriers while achieving the integration of efficient luminescence and luminance regulation is the current topical issue in QLET research and the key to the practicalization of the device.In this paper,the gate is directly added on the basis of high performance QLED matched functional layer energy levels and device processes,and the electroluminescence of high-quality quantum dots is integrated,and the enhancement of carrier transport by field-effect transistors is studied to improve electroluminescence.QLET with high brightness,high efficiency and luminescence modulation capability is prepared by controlling the carrier transport intensity to achieve fine adjustment of luminance.Specifically,this paper first constructs a bottom-gate vertical structure quantum dot light-emitting field-effect transistor,and studies the role and regulation principle of field-effect devices in QLET.Then,optimizes the conventional top-or bottom-gate structure QLET to vertical structure QLET with gate-all-around and investigates the formation of carrier aggregation channels and the enhancement of transport,as well as the enhancement of luminance efficiency and brightness.The main contents and research innovations of the graduation thesis are as follows:1.Design of bottom-gate vertical QLET and modulation of optoelectronic performanceThe vertical structure QLET with bottom-or top-gate has large carrier injection area and is compatible with QLED construction process.In this study,QLET devices with vertical bottom gate structure were fabricated by photolithography and ITO etching,using the idea of separating"light emitting region"from"gate field effect control region".Then,the field effect is used to regulate the efficiency of hole injection to optimize the electron/hole injection ratio of quantum dot electroluminescent transistor,effectively suppressing non-radiative recombination and enhancing the luminescence efficiency and brightness of the device.Finally,by optimizing the device structure to change the duty ratio of the field effect region,the electroluminescence performance of the three-color QLET devices has been improved,and the brightness of the red and green devices has been increased to obtain the external quantum efficiency(～20%)close to the theoretical limit.The luminance enhancement of blue devices is 23.93%to 12,480 cd/m~2 and the EQE enhancement is 19.97%to 10.39%.The study achieves an improvement in luminescence performance based on high-performance QLEDs by gate optimization of hole injection,confirming the advantages and value of constructing QLET devices with both luminescence and efficiency using the idea of separating the luminescence unit from the field modulation unit.It opens up new avenues for the expansion of QLED applications.2.Vertical QLET with gate-all-around structure for carrier modulation and luminescence enhancementFirstly,the idea of separating the"light emitting unit"from the"gate control unit"has been adopted to construct vertical QLET with side gate on the base of high-performance electroluminescent units(QLED).Then,we study the carrier accumulation and the formation of transport channel under the action of side gate electrode,as well as the mechanism of device efficiency and luminance enhancement;On this basis,we simplify the device structure,to extend the side gate to the encircled gate,and connect with the bottom ITO drain electrode,achieving the enhancement of luminance efficiency and device luminance.It has achieved external quantum efficiency(EQE)improvements of 27%,53.9%and 37.6%for red,green and blue QLET devices,reaching 14.32%,11.93%and 8.75%,with a brightness of 41,900 cd/m~2,180,800 cd/m~2 and 6,324cd/m~2.Finally,the device is simulated to explain the enhanced optoelectronic performance at positive gate voltage.This study provides a new strategy for the integration of electroluminescence enhancement and carrier modulation in optoelectronic devices.