Fabrication of Highly Luminescent Quasi Two-Dimensional CsPbBr₃ Perovskite Films in High Humidity Air for Light-Emitting Diodes

Abstract

Perovskite light-emitting diodes (LEDs) have attracted extensive attention in recent years due to their outstanding performance and promise in lighting and display applications. However, the fabrication of perovskite LEDs usually requires a low-humidity atmosphere, which is unfavorable for industrial production. Herein, we report an effective strategy to fabricate highly luminescent quasi two-dimensional CsPbBr3 perovskite films in an ambient atmosphere with a humidity up to 60%. We reveal that the hole transport layer (HTL) plays a significant role in the morphology and optical properties of the perovskite films. Using hydrophobic self-assembled monolayer materials as HTLs can remarkably improve the quality of the perovskite films processed in high humidity air. The resultant perovskite LEDs show reduced leakage current and significantly enhanced performance. Furthermore, surface treatment is conducted to prevent water invasion and promote radiative recombination in perovskite films and LEDs. Eventually, the perovskite LEDs exhibit bright green emission with an external quantum efficiency of 4.87%. The present work provides a feasible pathway to overcome the humidity limitation for obtaining bright perovskite films and LEDs, which would contribute to further reducing the fabrication cost of perovskite LEDs and promoting their applications.

Modifying Low-Temperature-Annealed NiOx Nanoparticle Films for Improved Performance of Perovskite Light-Emitting Diodes

“…Figure 2a,b shows the Ni 2p spectra of the pristine NiO x and PSSNa-modified NiO x films. By fitting the XPS results, 16 it can be seen that Ni 2+ and Ni 3+ components exist in both films, and the signals at 853.9 eV are attributed to the NiO and the 855.6 and 857.5 eV signals correspond to the Ni 2p of Ni 2 O 3 and NiOOH, respectively. 32−34 It is found that the PSSNa modification increases the Ni 3+ /Ni 2+ ratio in the NiO x films, with the details given in Table S1.…”

“…For PeLEDs, the device performance is dependent on not only the perovskite-emitting layer but also the bottom hole transport materials (HTMs), which can affect both the hole injection efficiency and the perovskite film quality. , Poly­(3,4-ethyenedioxythiophene):poly­(styrene sulfonate) (PEDOT:PSS) is a widely used HTM in PeLEDs due to the advantages of easy processability and good carrier transport capability. , However, the inherent acidity and hygroscopicity of PEDOT:PSS would inevitably deteriorate the electrode and perovskite, leading to undesirable perovskite films and less-ideal LED device efficiency and stability. − As an inorganic p-type semiconductor, NiO x is an alternative HTM for PeLEDs due to the attractive properties such as high optical transparency, good chemical and physical stability, and outstanding hole transporting ability as well as electron-blocking ability. − Lee et al found that the use of the NiO x film, in comparison with PEDOT:PSS, enabled the growth of higher crystalline perovskite with reduced trap density of states, resulting in improved optical properties and stability of PeLEDs. Wang et al constructed green PeLEDs using NiO x HTM and achieved a threefold improvement in EQE and lifetime compared to the devices based on PEDOT:PSS.…”

Reducing Nonradiative Losses of Air‐Processed Perovskite Films via Interface Modification for Bright and Efficient Light Emitting Diodes

“…In the past few years, strategies have been explored to fabricate perovskite luminescent films and LEDs in ambient air. [16][17][18][19][20] For example, Liu et al report the fabrication of quasi-2D formamidinium lead bromide (FAPbBr 3 ) perovskite films, and realize efficient green LEDs. [16] However, the humidity and temperature of the environment have to be strictly controlled, which is unfavorable for low-cost industrial production.…”

“…When processing in a high humidity air, the commonly used poly(3,4ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) hole transport layer (HTL) can easily adsorb water and deteriorate the perovskite films. [18,19] To overcome this issue, in our recent work, we utilized more hydrophobic self-assembled monolayer (SAM) to replace the PEDOT:PSS, which enabled successful deposition of quasi-2D CsPbBr 3 perovskite films under ambient air with humidity up to 60%. [19] Nevertheless, the nonradiative losses at the interface and in the perovskite films are still prominent, leading to unsatisfactory performance of the air-processed LEDs.…”

“…[18,19] To overcome this issue, in our recent work, we utilized more hydrophobic self-assembled monolayer (SAM) to replace the PEDOT:PSS, which enabled successful deposition of quasi-2D CsPbBr 3 perovskite films under ambient air with humidity up to 60%. [19] Nevertheless, the nonradiative losses at the interface and in the perovskite films are still prominent, leading to unsatisfactory performance of the air-processed LEDs.…”