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.