Research On Perovskite Hybrid Light Emitting Diodes With LiF Inserting Layer Structure

Metal halide perovskite materials have drawn widespread attention thanks to its excellent opto-electronic property including adjustable bandgap,narrow emission spectrum,high carrier mobility,high photoluminescent efficiency and solution processable ability,et al.The interface between hole transport layer(HTL)and perovskite emitting layer plays a key role in the electroluminescence(EL)performance of Pe LEDs.In this paper,a novel device structure with an ultrathin insulating modification layer(IML)inserted between HTL and perovskite layer is provided to promote the EL performance of Pe LEDs.The feasibility of the method is confirmed by the simulation and experimental method,followed by the fabrication of Pe LEDs with LiF as the material of the IML.Moreover,Ga N-Pero hybrid LEDs are fabricated for the first time and the opto-electronic properties of the hybrid LEDs under different driving modes are thoroughly investigated.The detailed research contents are as follow:(1)Simulation of Pe LEDs with insulating modification layerFor the simulation,Pe LEDs with traditional device structure and IML device structure are select as the research objects,respectively.Using the simulation method,a series of parameters including the valanced band maximum(VBM)of the HTL,the thickness of the IML,the VBM of the IML and the bandgap of the perovskite are systematically investigated.Moreover,single carrier devices with LiF as the material of IML are fabricated.By comparing the electron and hole current density of single carrier devices with various thickness of LiF modification layer,the effect of LiF modification layer on the charge injection balance of Pe LEDs is proved,which is in accordance with the simulation result.(2)Manufacturing and performance study on Pe LEDs with ultrathin LiF interface modification layerTaking LiF as the material of IML,further researches on the effects of LiF layer including the morphology modification effect on both PEDOT:PSS and perovskite layer,as well as the passivation effect on the PEDOT:PSS/perovskite interface are conducted.For the device performance,the optimal Pe LED with a 2 nm LiF layer exhibits a significantly decreased turn-on voltage of 2.8 V compared to 4.9 V of the pristine device without a LiF layer,combined with an over 100-fold enhancement in the maximum luminance(10415 cd/m~2),current efficiency(12.1 cd/A),and external quantum efficiency(3.5%).(3)Manufacturing and performance study on Ga N-Pero hybrid LEDsTaking ITO as the intermediate connecting electrode,Ga N-Pero hybrid LEDs with independently controllable emitting units are fabricated.When light the Pe LED unit alone,the optimal device exhibited high maximum luminance and EQE of 18482 cd/m~2 and 11.4%,respectively.By simultaneously lighting up the Ga N-Pero hybrid LEDs and the red Pe LEDs,the color gamut of the Ga N-Pero hybrid LEDs can reach up to 110%NTSC standard.Moreover,further investigations on driving modes of Ga N-Pero hybrid LEDs show that the parallel mode is not suitable for Ga N-Pero hybrid LEDs.For the Comparison of the DC mode and PWM mode,Ga N-Pero hybrid LEDs can achieve a higher maximum luminescence in the spectrum range of blue when adopting DC mode,while the current efficiency of the devices in PWM mode is better in the whole range of spectrum compared with DC mode.