Abstract
Organic light-emitting diode (OLED)-based display products have already emerged in the market and their efficiencies and lifetimes are sound at the comparatively low required luminance. To realize OLED for lighting application sooner, higher light quality and better power efficiency at elevated luminance are still demanded. This review reveals the advantages of incorporating a nano-scale carrier modulation layer (CML), also known as a spacer, carrier-regulating layer, or interlayer, among other terms, to tune the chromaticity and color temperature as well as to markedly improve the device efficiency and color rendering index (CRI) for numerous OLED devices. The functions of the CML can be enhanced as multiple layers and blend structures are employed. At proper thickness, the employment of CML enables the device to balance the distribution of carriers in the two emissive zones and achieve high device efficiencies and long operational lifetime while maintaining very high CRI. Moreover, we have also reviewed the effect of using CML on the most significant characteristics of OLEDs, namely: efficiency, luminance, life-time, CRI, SRI, chromaticity, and the color temperature, and see how the thickness tuning and selection of proper CML are crucial to effectively control the OLED device performance.
Highlights
Organic light-emitting diodes (OLEDs) have emerged as the most favorable alternative to liquid crystal displays (LCDs) in portable display devices like smartphones, smartwatches, digital cameras, MP3/MP4 players, etc
We have reviewed the effect of incorporating various different types of carrier modulation layer (CML) on device performance, e.g., efficiency, maximum luminance, operational lifetime, chromaticity, color temperature, color rendering index (CRI), spectrum resemblance index (SRI), and sunlight spectrum resemblance (SSR)
CML OLED in which the first CML thickness was kept at 10 nm and the second CML thickness varied from 5 to 2 nm; the maximum luminance increased from 5960 to 7740 cd·m−2 and the external quantum efficiency (EQE) increased from 4.3% to 4.5% at 1000 cd·m−2, the same as observed for single CML
Summary
Organic light-emitting diodes (OLEDs) have emerged as the most favorable alternative to liquid crystal displays (LCDs) in portable display devices like smartphones, smartwatches, digital cameras, MP3/MP4 players, etc. OLED devices, a large number of different approaches have been reported, such as thin device layer structures, low charge carrier injection barriers, high charge carriers (hole and electron) mobilities, balanced carrier injection, effective carrier confinement, effective host-to-guest energy transfer, a wider recombination zone, effective exciton generation on host, effective exciton confinement, p-i-n structures, and tandem structures [20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40] Several of these are especially effective in improving device efficiency at high applied luminance. We have discussed the effect of thickness, incorporation position, and functioning mechanism of single and double nano CMLs in a variety of OLED devices
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