High‐Throughput Combinatorial Optimizations of Perovskite Light‐Emitting Diodes Based on All‐Vacuum Deposition

Abstract

Light-emitting diodes (LEDs) based on lead halide perovskites demonstrate outstanding optoelectronic properties and are strong competitors for display and lighting applications. While previous halide perovskite LEDs are mainly produced via solution processing, here an all-vacuum processing method is employed to construct CsPbBr 3 LEDs because vacuum processing exhibits high reliability and easy integration with existing OLED facilities for mass production. The high-throughput combinatorial strategies are further adopted to study perovskite composition, annealing temperature, and functional layer thickness, thus significantly speeding up the optimization process. The best rigid device shows a current efficiency (CE) of 4.8 cd A −1 (EQE of 1.45%) at 2358 cd m −2 , and best flexible device shows a CE of 4.16 cd A −1 (EQE of 1.37%) at 2012 cd m −2 with good bending tolerance. Moreover, by choosing NiO x as the hole-injection layer, the CE is improved to 10.15 cd A −1 and EQE is improved to a record of 3.26% for perovskite LEDs produced by vacuum deposition. The time efficient combinatorial approaches can also be applied to optimize other perovskite LEDs.

Improved Performance for Thermally Evaporated Perovskite Light-Emitting Devices via Defect Passivation and Carrier Regulation

“…In addition, the multilayer PeLED (see Figure S2a) fabricated with the EML using a CsBr/PbBr 2 thickness ratio of 9.8:3.2 also presents the best overall optoelectronic performance, as shown in Figure S2b,c and Table S1. The device exhibits the lowest turn-on voltage of 3 V, a maximum luminance of 8662 cd m –2 , a maximum current efficiency of 4.52 cd A –1 , and a corresponding EQE of 1.27% that is comparable to the performance reported in the literature where PEDOT:PSS was used as the hole transport layer …”

“…Although the maximum luminance primarily limited by the current density shows a reduction to some extent, the maximum CE and EQE of the devices treated with PEABr (2 mg mL –1 ) were evidently improved to 14.64 cd A –1 and 4.10%, respectively, as shown in Figure b,c and Table . Such results are the highest current efficiency and EQE for the thermal-evaporation prepared green PeLEDs compared with those reported in the literature. ,, …”

“…Such results are the highest current efficiency and EQE for the thermal-evaporation prepared green PeLEDs compared with those reported in the literature. 23,28,29 The variation in J−V curves as well as the promotion in light-emission efficiency after the PEABr modification demonstrates that PEABr not only passivates the nonradiative traps but also regulates the carrier transport, making a better balance between the holes and the electrons. To elucidate this, hole-only and electron-only devices are constructed (see Figure S7) to investigate whether the electrons and holes injected into the perovskite layer are balanced.…”

Tailoring of Photoluminescence Properties in All‐Vacuum Deposited Perovskite via Ruddlesden–Popper Faults

“…As mentioned above, CsPbBr 3 perovskites belong to the orthorhombic phase at room temperature, which is also proved experimentally for both solution [ 26 ] and full‐evaporation [ 14 ] processes by X‐ray diffraction (XRD). The corresponding XRD spectrum for CsPbBr 3 perovskite film studied here is presented in Figure S2 (Supporting Information), which shows (002) and (004) peaks, indicating preferential growth of the films along the c axis.…”

Showerhead-assisted chemical vapor deposition of CsPbBr3 films for LED applications

“…7c), which is around two orders of magnitude lower compared to that of the spin-coating reference (11,500 cd/m 2 ). In literature, PeLEDs achieve a maximum luminance between 0.5 and 9442 cd/m 2 in the case of thermally evaporated CsPbBr 3 [18,51] and 5,025 cd/ m 2 for CVD-based CsPbBr 3 [22]. The external quantum efficiency (EQE) is calculated to be 0.003%, which is several orders of magnitude lower compared to that of the reference PeLED (1.1%).…”