Hole Transport Layer Modification for Highly Efficient Divalent Ion-Doped Pure Blue Perovskite Light-Emitting Diodes

摘要

Divalent ions-doping has recently been developed as a new approach toblue perovskite light emitting diodes (LEDs) with improved spectral stability.However, the efficiency of these perovskite LEDs, especially in the pure blueregion, is still far behind their red- and green-emissive counterparts. Here, amethod to improve the device efficiency of strontium ion (Sr~(2+))-doped pureblue perovskite LEDs, prominently by modifying the hole transport layer, isreported. Mixing a small amount of poly(9,9-di-n-octylfluorene-alt-(1,4-phenylene-(4-sec-butylphenyl)imino)-1,4-phenylene) (TFB) into the hole transportlayer poly(9-vinylcarbazole) (PVK) remarkably improves the morphology andreduces the trap states of Sr~(2+)-doped perovskite films. As a result, a pureblue LED emitting at 470 nm is obtained and shows a high external quantumefficiency of 2.24% with stable electroluminescence spectra under a forwardbias of up to 8 V, representing the best performance reported in the divalentions-doped pure blue perovskites so far. The work opens up the way for thedevelopment of efficient pure blue perovskite LEDs.