Design and performance of sulfur and selenium-substituted triarylboron D3-A TADF emitters for OLED applications

Date

2024-11-01

Author

Karakurt, Oğuzhan
Demirgezer, Elif Fatma
Daştemir, Murat
Cakmaktepe, Semih Can
Miranda-Salinas, Hector
Aksoy, Erkan
Danos, Andrew
Monkman, Andrew
Yıldırım, Erol
Çırpan, Ali

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This study presents the design, synthesis, and comprehensive theoretical and photophysical analysis of two new D3-A type thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diode (OLED) applications. Utilizing a triarylboron core as the electron-accepting group and phenothiazine (PTZ) or phenoselenazine (PSZ) as electron-donating units, the molecules BTP-S and BTP-Se were developed. The D3-A structure supports the separation of frontier molecular orbitals (FMOs), leading to minimized singlet-triplet energy gaps (ΔEST), which are crucial for the TADF mechanism. Density functional theory (DFT) calculations presented that BTP-S and BTP-Se exhibit band gaps (Eg) of 2.52 and 3.23 eV, respectively, with BTP-S showing an ΔEST value as low as 0.007 eV for the S1-T1 transition at the lowest energy conformation. Photophysical studies revealed high photoluminescence quantum yields (PLQYs) for both compounds, with BTP-S achieving up to 85 % in mCP films and BTP-Se up to 59 %. In vacuum-processed OLEDs, BTP-S achieved a maximum external quantum efficiency (EQE) of 25.3 %, a current efficiency (ηc) of 195.8 cd/A, and a maximum luminance (Lmax) of 17356 cd/m2, while BTP-Se reached an EQE of 7.5 %, an ηc of 132.19 cd/A, and an Lmax of 16826 cd/m2 likely limited by the contributions of a folded-donor conformer enabled by the Se substitution. These findings underscore the impact of donor unit selection and conformation on the TADF characteristics, and provide valuable insights for designing high-performance OLED materials.

Subject Keywords

OLED, Phenoselenazine, Phenothiazine, TADF, Triaryl-boron

URI

https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85202707216&origin=inward
https://hdl.handle.net/11511/111126

Collections

Department of Chemistry, Article