Construction of Robust Cadmium-Free Cu-In-Zn-S Nanocrystals and Polyfluorene Derivatives Hybrid Emissive Layer for Stable Electroluminescent White Light-Emitting Devices.

Combination of the merit of inorganic nanocrystals (NCs) and solution-processed conjugated polymer is a convenient strategy to obtain stable and efficient electroluminescent white-light-emitting diodes (el-WLEDs). In this work, an el-WLED was fabricated on the basis of Cd-free Cu-In-Zn-S (CIZS)/ZnS NCs blending with polyfluorene derivative poly[4-(octyloxy)-9,9-diphenylfluoren-2,7-diyl]-co-[5-(octyloxy)-9,9-diphenylfluoren-2,7-diyl] (PODPF), which exhibited a stable white light emission with a color rendering index value of 85. Meanwhile, it had a stable spectrum under high voltage due to the extremely weak energy transfer between PODPF and CIZS/ZnS NCs. To further improve the device performance, PC9O4 was used to replace PODPF, which presented better solubility and smoother film-forming properties. Thus, the maximum external quantum efficiency (EQE) of the optimized el-WLED was increased by 221% while maintaining a stable spectrum under high voltage. This work may provide a great foundation on color mixing cadmium-free el-WLEDs.