Highly Stable Inverted CdSe/ZnS-Based Light-Emitting Diodes by Nonvacuum Technique ZTO as the Electron-Transport Layer

Abstract

CdSe/ZnS quantum dots (QDs) have attracted great consideration from investigators owing to their excellent photo-physical characteristics and application in quantum dot light-emitting diodes (QD-LEDs). The CdSe/ZnS-based inverted QD-LEDs structure uses high-quality semiconductors electron transport layers (ETLs), a multilayered hole transporting layers (HTLs). In QD-LED, designing a device structure with a minimum energy barrier between adjacent layers is very important to achieve high efficiency. A high mobility polymer of poly (9,9-dioctylfluorene-co-N-(4-(3-methylpropyl)) diphenylamine (TFB) was doped with 4,4′-bis-(carbazole-9-yl) biphenyl (CBP) with deep energy level to produce composite TFB:CBP holes to solve energy mismatch (HTL). In addition, we also improved the QD-LED device structure by using zinc tin oxide (ZTO) as ETL to improve device efficiency. The device turn-on voltage Vt (1 cd m−2) with ZTO ETL reduced from 2.4 V to 1.9 V significantly. Furthermore, invert structure devices exhibit luminance of 4296 cd m−2, current-efficiency (CE) of 7.36 cd A−1, and external-quantum efficiency (EQE) of 3.97%. For the QD-LED based on ZTO, the device efficiency is improved by 1.7 times.

Solution Processed Light Emitting Diode Based on InP Quantum Dots with Hybrid Emissive Layer

“…Although the hole mobility in organic HTL is much lower than the electron movement in ETL, the unbalanced carrier insertion within the QD-LEDs is mainly caused by the inadequate hole injection of the organic HTL. To establish carrier-injection balance in the QD-LEDs, It is still considered efficient to design a distinct HTL that has excellent hole mobility as well as deep HOMO [15]- [17]. Additionally, recent studies have shown that the performance of QD-LEDs can degrade faster due to electron leakage from organic HTL.…”