Microcavity‐Enhanced Blue Organic Light‐Emitting Diode for High‐Quality Monochromatic Light Source with Nonquarterwave Structural Design

Abstract

Despite their rapid development, organic light‐emitting diodes (OLEDs) are limited to display and lighting applications, and exploiting the application and development of OLEDs has become one of the critical issues. In this study, a new type of distributed Bragg reflector (DBR) with low absorption spacer as a bottom mirror is developed through nonquarterwave structural design. Different factors affecting the electroluminescence (EL) properties of microcavity OLEDs (MOLEDs) are investigated by using the optical microcavities with different structures to regulate the EL properties of 4,4′‐bis[(N‐carbazole)styryl] biphenyl (BSB‐Cz). The optimized MOLEDs with quarterwave DBRs exhibited a maximum external quantum efficiency of 8.86 ± 0.06%, demonstrating an enhancement of 79% compared to a reference device. Under the premise of almost not changing the electrical injection of the functional layer materials in the cavity, the spectral full‐width at half maximum of MOLEDs with a nonquarterwave structural design is as narrow as 2 ± 0.05 nm. These improvements are not only suitable for small organic molecules or polymeric materials, but also for novel nanoluminescent materials, such as quantum dots, perovskites, etc. Overall, the current study suggests the general applicability of this novel concept to obtain high‐quality monochromatic light, irrespective of the type of materials used.

Spectral Narrowing and Enhancement of Directional Emission of Perovskite Light Emitting Diode by Microcavity

“…In order to achieve the optimized resonance enhancement effect and device performance, we need to systematically design the thickness of each layer. Under the resonance condition, the emission enhancement factor Ge along the normal direction is given by [33,40,47] where R 1 and R 2 are the reflectivities of DBR and Al mirrors, respectively, 𝜉 is the antinode enhancement factor, 𝜏 cav and 𝜏 are the lifetimes of spontaneous emissions in resonant microcavity and free space. According to Purcell effect, the spontaneous emission rate of resonant photons is enhanced in microcavity, [53] but this effect is unobvious for planar microcavities.…”

“…[47] On the contrary, microcavity exhibits the suppression of emission when the cavity mode is not in the range of natural spectrum. The integrated enhancement factor G int over all wavelengths is given by [33,40,47]…”

“…Thereby, MCLED is considered as a good compromise between VCSELs and LEDs and has been adopted in many optoelectronic systems that requires high light coupling efficiency, such as plastic optical fiber (POF) communication, printers, optical scanners, and so on. [35] Numerous studies on MCLEDs have been reported using compound semiconductor, [36][37][38][39] organic, [40][41][42][43][44][45][46] or quantum dots (QDs) [47] materials as emission layer, significantly improved LED performances in terms of directionality of emission, spectral purity, and light extraction were observed. Red microcavity QDs and quasi-2D perovskite top-emission light emitting diodes have been realized by metal cavities [48,49] to enhance EQE recently.…”

Toward Electrically Pumped Organic Lasers: A Review and Outlook on Material Developments and Resonator Architectures

“…[ 122 ] Lin et al reported narrow‐band pure‐UV (FWHM ≈ 9.95 nm) and blue (FWHM ≈ 8 nm) electroluminescence from microcavity OLEDs using 1,2‐di‐ p ‐tolyl‐1H‐phenanthro[9,10‐d]‐imidazole (Tol‐PPI) and BSB‐Cz as emitters, respectively. [ 123 ]…”

Enhancing the Light Output‐Coupling of Inverted Top‐Emitting Organic Light‐Emitting Diodes by Using the Localized Surface Plasmon Resonance of Ag Nanoparticles

“…

maximum (FWHM) and current efficiency (CE) of the TEOLEDs are significantly optimized owing to the micro-cavity effect of the top-emitting structure, promoting the applications in ultra-high-definition displays and micro-displays. [11,12] However, one major challenge of the TEOLEDs is the severe waveguide and plasmonic losses, which hinders the light outputcoupling and results in the low external quantum efficiency (EQE). [13,14] Introducing the localized surface plasmon resonance (LSPR) in the device is an effective way to increase the EQE of the OLEDs.

…”