| Quantum dot light-emitting diode(QLED)is considered to be an ideal next-generation display device due to its high color purity,tunable luminescence wavelength,and solution processability.Non-toxic and efficient indium phosphide(InP)has attracted great attention due to its environmental protection.Recently,the emerging perovskite light-emitting diode(Pe LED)has also attracted widespread attention due to its high color purity,adjustable emission wavelength,solution processing,and low cost.Due to the energy level mismatch,high mobility and severe quenching,ZnO is not suitable in InP QLED.To solve these problems,Zn Mg O are used to replace ZnO as the electron transport layer.On the premise of not deteriorating the morphology and roughnesse of the film,Zn Mg O has fewer defect states,which can reduce the quenching of fluorescence of quantum dots,increase the ratio of radiation recombination,and prolong the average exciton lifetime.The energy levels of Zn Mg O and InP are more matched,which reduces the electron injection barrier,resulting in reducing the turn-on voltage of InP QLED from 2.51 V to 2.32 V and increasing of current density in diffusion current region.At the same time,since the quenching is reduced,the current efficiency is increased from 4.03 cd/A to 6.38 cd/A,and the maximum brightness is increased sharply from 1.0×10~4 cd/m~2 to 1.3×10~4 cd/m~2,which are an enhancement of 60%and 30%,respectively.In addition,the thickness and the annealing temperature of the quantum dots layer are further optimized to 23 nm and 90℃,respectively,the current efficiency is further improved to 10.44 cd/A,and the maximum external quantum efficiency(EQE)is 7.3%.After positive aging for 48 hours,the maximum EQE of the device reaches up to 8%.This is attributed to the decrease in the proportion of oxygen vacancies in Zn Mg O from 31.1%to 27.8%,which results in the deterioration of the electron transport properties and the decrease of electron current density after storage.From the perspective of the materials and the substrate,p-fluorophenethylamine bromide is selected as the component of the organic ammonium salt in the perovskite precursor due to its suitable optical band gap.And polyethylenimine ethoxylated(PEIE)with the smallest contact angle serves as the inter-layer between ZnO and the perovskite layer.Simultaneously,a precursor with an organic ammonium salt ratio of 125%is selected from the aspects of film optical properties,film morphology,and crystallization.And the thickness of PEIE is adjusted to 5 nm.To further blue-shift the luminescence of the perovskite film and refine the crystal grains,the photoluminescence peak of the perovskite film is blue-shifted from 481 nm to 467nm with chlorobenzene as an anti-solvent,and the full width at half maximum is reduced from98 nm to 27 nm,improving the color purity.In the meantime,the photoluminescence quantum yield and the average lifetime of the film are doubled and the radiation recombination ratio is increased.The film morphology is improved and the exciton binding energy of the film is increased from 114.77 me V to 165.38 me V attributing to the quantum confinement effect.The maximum brightness of the finally obtained inverted quasi-2D blue Pe LED is increased to 418cd/m~2 and the maximum EQE is increased to 0.44%,which is 10-fold comparing with the pristine condition.Finally,the method of elemental analysis proves that ZnO will still gradually diffuse into the perovskite film,causing the organic ammonium salt to deprotonate and decompose,which limits the performance of the inverted quasi-2D PeLED. |
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