The Effect of Cation Doped ZnO Electron Transport Layer for Pure Blue Emitting Zntese/ZnSe/ZnS Quantum Dot Light Emitting Diodes

Colloidal quantum dot light emitting diodes (QLED) has considered as next generation display technology due to their accurate color information, high brightness, with low process cost, and potential flexible substrates. Red and green QLED achieved nearly the efficiency of theoretical limitation by optimizing quantum dot materials and device architecture with the tremendous efforts of many fellow researchers [1,2]. However, the authentic blue color QLED with high performance and high stability is yet remained as a obstacle for the commercialization. Herein, we report the fabrication of ZnTeSe based blue QLED device with multi shell quantum dots with very high quantum yield over >90% at 443nm with narrow FWHM of 15 nm. The peak wavelength of quantum dot could be tuned with the different Te/Se ratio of the core and the thickness of intermediate ZnSe shell. With the combination of zinc magnesium oxide (ZMO), which is the most common electron transport layer (ETL) for blue QLED, and our highly luminescent blue quantum dot, bright blue QLEDs with the max luminance of 700 cd/m2 in the inverted structure are demonstrated. Moreover, to obtain the better-performed and stable electron transport layer, different cations such as lithium, nickel, aluminum, cerium, erbium and indium-doped zinc oxides were successfully synthesized and studied. we have analyzed the band gap of ZnO can be fine tuned by doping of different cations and the effect of different zinc oxide in the device will be tested in the further study. According to the recent researches of the device stability of blue QLED [3,4], inferior stability of blue QLED is originated from the interface of ETL and quantum dots. I believe that the study of various ETL materials can give us a key to solve the poor lifetime problem of blue QLED. Reference 1. Li, Y., Hou, X., Dai, X., Yao, Z., Lv, L., Jin, Y., & Peng, X. (2019). Stoichiometry-Controlled InP-Based Quantum Dots: Synthesis, Photoluminescence, and Electroluminescence. Journal of the American Chemical Society, 141(16), 6448–6452. 2. Won, Y.-H., Cho, O., Kim, T., Chung, D.-Y., Kim, T., Chung, H., ... Jang, E. (2019). Highly efficient and stable InP/ZnSe/ZnS quantum dot light-emitting diodes. Nature, 575(7784), 634–638. 3. Chen, S., Cao, W., Liu, T., Tsang, S.-W., Yang, Y., Yan, X., & Qian, L. (2019). On the degradation mechanisms of quantum-dot light-emitting diodes. Nature Communications, 10(1), 765. 4. Kim, T., Kim, K.-H., Kim, S., Choi, S.-M., Jang, H., Seo, H.-K., ... Jang, E. (2020). Efficient and stable blue quantum dot light-emitting diode. Nature, 586(7829), 385–389.