Enhancement of Light Extraction Efficiency and Suppression of Roll‐Off Characteristics of Thermally Activated Delayed Fluorescence Organic Light‐Emitting Diodes by Inserting Nanoscale Pixel‐Defining Layer

• Published in: Advanced electronic materials 2023-04, Vol.9 (4), p.n/a
• Main Authors: Lee, Seungwon, Park, Jun‐Young, Park, Jaewon, Bi, Jian Cheng, Kang, Byeongwoo, Hwang, Young Hyun, Seok, Jiwon, Park, Young Wook, Ju, Byeong‐Kwon
• Format: Article
• Language: English
• Subjects: Diffusion layers; Efficiency; efficiency roll‐off; Emission; Energy transfer; Excitons; finite‐difference time‐domain simulations; Fluorescence; Glass substrates; Interfaces; laser interference lithography; Lasers; Light; light extractions; Organic chemistry; Organic light emitting diodes; Pixels; Plasma etching; Polaritons; Simulation
• ISSN: 2199-160X; 2199-160X
• DOI: 10.1002/aelm.202201264

Thermally activated delayed fluorescence (TADF) organic molecules are considered the most suitable for blue organic light‐emitting diodes (OLEDs) after extensive research; however, they are plagued by issues of internally guided light and the roll‐off characteristics contributed by triplet exciton‐utilized emission. Thus, this study leverages exciton diffusion guidance and energy extraction to simultaneously achieve optical efficiency enhancement and roll‐off characteristic suppression of mixed‐host blue TADF OLEDs. The array of nanopixels, defined by the inserted nanoscale pixel‐defining layer (nPDL), spatially separates the excitons and polarons, resulting in the exacerbation of triplet quenching by securing exciton diffusion. Furthermore, through the formation of a metal cathode with a corrugated profile, nonradiative energy transfer to the surface plasmon polaritons is capitalized via Bragg diffraction, thereby boosting the emission efficiency. The structure of the nPDL is judiciously determined by finite‐difference time‐domain computational analysis. Consequently, the device with the optimized nPDL demonstrates 88.4%, 118.8%, and 108.8% improvements in external quantum, current, and power efficiencies, respectively, compared to the reference. Moreover, the critical luminance, which quantifies the degree of roll‐off, is improved by 83.7%. This pioneering demonstration of hybridizing the material combination and nanopatterning techniques is expected to provide new insights for designing high‐performance OLEDs. By constructing an array of nanopixels via insertion of the nanoline insulator structure, optical efficiency enhancement and roll‐off characteristic suppression of the third‐generation blue organic light‐emitting diodes are simultaneously achieved. The nanoarrayed device extracts guided light through Bragg diffraction and alleviates triplet exciton quenching through exciton diffusion guidance. Synergized with the mixed‐host emission system, the high‐performance blue‐emitting device is demonstrated.