溶液法制备的金属掺杂氧化镍空穴注入层在钙钛矿发光二极管上的应用

Perovskite light-emitting diodes based on solution-processed metal-doped nickel oxide hole injection layer

甲脒基钙钛矿(FAPbX3)纳米晶(NCs)具有成本低、色纯度高、吸收范围广、带隙可调等特点,在照明显示与光伏领域中表现出良好的应用前景.然而传统钙钛矿发光二极管(LEDs)的空穴注入层材料--PEDOT:PSS,由于其固有的吸湿性和酸性,严重影响着器件的稳定性,而器件的稳定性始终是阻碍钙钛矿发光器件成为实际应用的关键因素之一.本文首次使用溶液法制备的氧化镍(NiO)薄膜作为溴基甲脒钙钛矿(FAPbBr3)NCs LEDs的空穴注入层,降低空穴注人层对钙钛矿发光层的影响,获得了高效且稳定的钙钛矿发光器件,器件寿命是基于PEDOT:PSS的器件的2.3倍.通过适当浓度的金属掺杂(Cs:NiO/Li:NiO),可以有效改善器件的电荷平衡,从而进一步提高FAPbBr3 NCs LEDs的性能.基于掺杂2 mol%Cs的NiO的器件表现出最优异的光电性质,其最大亮度,最大电流效率,峰值EQE分别为2970 cd·m-2,43.0 cd·A-1和11.0%;相比于传统的PEDOT:PSS基的器件,效率提高了近2倍.

Formamidinium lead bromide(FAPbBr3)perovskite nanocrystals(NCs)have attracted great attention due to their remarkable performances of low cost,high color purity and tunable band gap.However,in a typical FAPbBr3 perovskite light-emitting diode(LED),PEDOT:PSS,with hygroscopic and acidic nature,serves as a hole injection layer(HIL),thus leading to the device stability to decrease seriously.Device stability is one critical issue that needs improving for future applications.Here in this study,the nickel oxide(NiO)film prepared by the solution method is adopted as the HIL of the FAPbBr3 perovskite LED to substitute detrimental PEDOT:PSS.Compared with the control device with PEDOT:PSS HIL,the resulting LED based on NiO film has the operating lifetime twice as great as that based on the PEDOT:PSS film.For further enhancing the performance of FAPbBr3 LED,two metal dopants(Cs and Li)are introduced to improve the hole injection capability of NiO film and the charge carriers’balance of device.With Hall measurements,both NiO and Cs/Li-doped NiO demonstrate a full p-type semiconductor characteristic.Increasing the doping concentration in the film can increase the carrier concentration and reduce the carrier mobility.This decreased carrier mobility results from the increased scattering due to grain boundaries and impurity phases,seriously at high Cs/Li concentration.As a result,the device,based on the NiO film(doping 2 mol%Cs)shows the best performance with a maximum brightness value of 2970 cd/m2,current efficiency of 43 cd/A and external quantum efficiency(EQE)of 11.0%,thus its efficiency is increased nearly by twice compared with that of the PEDOT:PSS-based device.The results pave the way for making highly efficient and stability perovskite LEDs based on FAPbBr3 NCs.