Red Perovskite Light‐Emitting Diodes with Efficiency Exceeding 25% Realized by Co‐Spacer Cations

Abstract

Perovskite light-emitting diodes (PeLEDs) own great attention in recent years, due to their narrow emission bandwidth and tunable emission spectrum. E cient red emission is one of most important part for lighting and display. Quasi-two-dimensional (quasi-2D) perovskite could deliver high emission e ciency due to the strong carrier con nement, while the external quantum e ciencies (EQE) of red quasi-2D PeLEDs are ine cient at present, which is due to the complex distribution of different n-value phases in quasi-2D perovskite lms. Here, we nely control the phase distribution of the quasi-2D perovskite by mixing two different large organic cations, which effectively reduce the amount of smaller n index phases, meanwhile the passivation of lead and halide defects in perovskite lms is realized.Accordingly, the PeLEDs showed 25.8% EQE and 1300 cd•m-2 maximum brightness at 680 nm, which exhibit the highest performance for red PeLEDs up to now. Full TextSolution-processed metal halide perovskites have attracted considerable research interest as a new type of semiconductor materials, which has been utilized in solar cells, light-emitting diodes and other optoelectronic devices [1][2][3][4][5][6][7][8] . In particular, Perovskite light-emitting diodes (PeLEDs) have been conferred as the cutting-edging research due to their high performance [9][10][11][12][13][14][15][16] , red emission is very important in the eld of lighting and display. To date, the red PeLEDs have achieved signi cant external quantum e ciencies (EQE) that over 20%, most of them are based on the three-dimensional (3D) and quantum-dot (QD) perovskite material [17][18][19][20][21][22] .Compared with 3D and QD perovskite, quasi-two-dimensional (quasi-2D) perovskite could be more e cient emission material due to its higher exciton binding energy, multi-quantum-well structure and good charge transfer properties [23][24][25][26][27][28] . Ruddlesden-Popper perovskite (RPP) is generally described by the formula of L 2 A n-1 B n X 3n+1 as typical quasi-2D perovskites, which consist of large organic cation L, a small organic or cesium cation A, divalent metal cation B (lead or tin), and halide anion X (Cl -, Bror I -).Although the overall development of red LED is remarkable, the quasi-2D red LEDs are still in arrears of e ciency. The reason may be that ne control of quasi-2D perovskite phase (represents the thickness of the [PbI 6 ] 4octahedra layers capped by the L cations [28][29][30][31] ) distribution is a great challenge, which make the inferior charge injection and serious non-radiative recombination.In this work, we report a general strategy of cospacer cations to control the phase distribution in RPP lms, by mixing a representative of phenethylammonium iodide (PEAI)/ 3-uorophenylethylammonium iodide (m-F-PEA) and 1-naphthylmethylammonium iodide (NMAI) to alloy the RPP lms. These RPP lms show signi cant suppression of small index phase (n=2), and the carrier transport has been improved effectively. At the same time, the mixing of NMA can reduce the metall...

Suppressed Energy Transfer Loss of Dion–Jacobson Perovskite Enabled by DMSO Vapor Treatment for Efficient Sky-Blue Light-Emitting Diodes

“…Quasi-two-dimensional (quasi-2D) perovskites have been extensively studied for high-performance solar cells and light-emitting diodes, due to the easily modulated film properties such as the hydrophobicity, energy band gap, energy and charge transfer, and nonradiative recombination. − Especially for perovskite light-emitting diodes (PeLEDs), the external quantum efficiencies (EQEs) of the red and green quasi-2D PeLEDs are already higher than those of three-dimensional PeLEDs, exceeding 25% and 28%, respectively. − However, for lighting and display applications, the efficiencies of blue PeLEDs (including deep blue, blue, and sky blue) need to be further elevated. , Generally, the inefficient blue light emission is mainly related to strong nonradiative recombination, inefficient energy transfer, and unbalanced charge transport. , Compared to the perovskites with mixed halides of bromide and chloride, which are prone to form defects due to halide segregation, pure bromide quasi-2D perovskites show a greater potential for high-efficiency blue PeLEDs. , Notably, the phase distribution of quasi-2D perovskite films can be effectively modulated to significantly improve the energy transfer and in turn suppress the energy losses of the related nonradiative recombination. , …”

Efficient emission of quasi-two-dimensional perovskite films cast by inkjet printing for pixel-defined matrix light-emitting diodes

“…These characteristics have made them extremely promising candidates for LEDs for potential display applications. So far, the external quantum efficiency (EQE) of green and red PeLEDs has both exceeded 25% based on a spin-coating technology [4][5][6]. However, the spin-coating method cannot match the industrial manufacturing requirements of large-area, fine-patterned and high-density light-emitting pixel arrays, as well as colorful images for display applications.…”

Suppressing High-Order Phase for Efficient Pure Red Quasi-2D Perovskite Light-Emitting Diodes

“…Control and P/N-2.5 RPP films show pinhole-free and smooth morphologies with very low root-mean-square roughness (around 0.5 nm in an area of 1 μm × 1 μm), which helps to avoid leakage current in devices. 10 We fabricated quasi-2D PeLEDs with a device structure of ITO/PEDOT:PSS/poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB)/LiF (1.3 nm)/perovskite (∼45 nm)/2,2′,2″-(1,3,5-benzinetriyl)tris(1-phenyl-1H-benzimidazole) (TPBi, 40 nm)/LiF (1 nm)/Al (100 nm) (Figure S10, Supporting Information). The device performance is summarized in Figure 3, Table 1, and Figure S6.…”

“…Metal halide perovskite is a star material in the semiconductor field, especially in the field of light emitting diodes. − Because of their high color purity, wide color gamut, low cost, and facile solution processability, perovskite light emitting diodes (PeLEDs) are very promising to be used in future large-area displays and solid-state lighting. − Full-color displays have put forward strict requirements on the color purity of three red, green, and blue primary colors . In terms of red emission, the International Telecommunication Union (ITU) BT2020 Recommendation (Rec.…”

“…Surface morphologies of the RPP films were investigated by atomic force microscopy (AFM) (Figure S5 in the Supporting Information). Control and P/N-2.5 RPP films show pinhole-free and smooth morphologies with very low root-mean-square roughness (around 0.5 nm in an area of 1 μm × 1 μm), which helps to avoid leakage current in devices …”