Dicai Zhuang,Yingyu Wang,Qiuting Cai,Lanlan Zhai,He Huang,Guanghong Yang,Yun Yang,Lijie Zhang,Chao Zou
Quasi-two-dimensional perovskite has been widely used in blue perovskite light-emitting diodes. However, the performance of these devices is still hampered by random phase distribution, nonradiative recombination, and imbalanced carrier transport. In this work, an effective strategy is proposed to mitigate these limitations by inserting lithium salts at the interfaces between the hole transport layer (HTL) and the perovskite layer. The perovskite film on the inserted Li2CO3 layer exhibits reasonable n-value redistribution, which leads to the repressive nonradiation recombination and enhanced carrier transport. Moreover, the inserted Li2CO3 layer also improves the electrical conductivity of PEDOT:PSS and hinders indium ion diffusion from the PEDOT:PSS layer to the perovskite film, which inhibits exciton quenching and nonradiative recombination loss at the HTL/perovskite interface. Taking advantage of these merits, we have successfully fabricated efficient pure-blue PeLEDs with an external quantum efficiency of 6.2% at 472 nm and a luminance of 726 cd cm–2. The restraint of nonradiative recombination at the interface offers a promising approach for efficient pure-blue PeLEDs.
Metal halide perovskites have become the next-generation electroluminescent materials due to their excellent optoelectronic properties. In the last several years, there has been tremendous progress in the performance of red and green-light perovskite electroluminescent devices (PeLEDs) with external quantum efficiencies (EQEs) exceeding 14% and 21%, respectively. In contrast, blue PeLEDs are still in their infancy, due to their EQEs of below 1%. Therefore, the development of blue PeLEDs is sorely needed since blue light plays a vital role in achieving full-color and white-light emission. In order to improve the efficiency of blue PeLEDs, herein we introduce gold nanoparticles (Au NPs) into a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layer (HTL) to achieve a high performance blue PeLED with an emission wavelength of ∼475 nm. By introducing Au NPs, the optical properties of poly(ethylene oxide) (PEO):PEA2(CsPbBrxCl3−x)n−1PbBr4 perovskite films have been significantly improved leading to 3.8 times enhancement in fluorescence intensity. Based on this improvement, blue PeLEDs record a maximum luminance and EQE of ∼1110 cd m−2 and 1.64%, respectively, presenting one of the best performances among the blue PeLEDs reported so far. Finally, the PeLED performance improvement is attributed to the far-field surface plasmonic effect of Au NPs. This effect has originated from the interference between the original chromophore emission and the mirror-reflected emission of mirror-type substrates. This study not only reveals the function of Au NPs in the development of blue PeLEDs, but also offers new insights into the fundamental physics underlying the effect of surface plasmon resonance of Au NPs on perovskite light emitting devices.
Hole-injection layers (HILs) play crucial roles in enhancing the performance of perovskite light-emitting diodes (PeLEDs) by lowering the energy barrier between the anode and the hole-transport layer (HTL). However, the commonly employed HIL, poly( 3 , 4 -ethylenedioxythiophene): polystyrene sulfonic acid (PEDOT: PSS) has notable drawbacks, such as extreme acidity and susceptibility to corrosion, which severely hampers device efficiency and stability. Herein, a self-assembled monolayer (SAM)-[ 2 -( 9H -Carbazol- 9 -yl) ethyl] phosphonic acid (2PACz) instead of PEDOT: PSS was employed in PeLEDs, which could reduce the negative impacts on neighboring perovskite sites and indium tin oxide electrodes. To obtain favorable energy level alignment between 2PACz and the perovskite layer, poly( 9 -vinylcarbazole) (PVK) was introduced as an indispensable HTL. Consequently, the 2PACz/PVK-based deep-blue PeLEDs exhibit a lower turn-on voltage of 3.20 V, and a peak external quantum efficiency of 4.42 % at 467 nm, which is a threefold improvement over the control devices. This impressive performance boost can be attributed to the reduction in interfacial defects and the improved balance of carrier injection, leading to more efficient light emission. Our study not only introduces an innovative and cost-effective HIL solution for PeLEDs but also provides valuable insights and guidance for the development of highly efficient and stable PeLEDs in the future.
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