Research Projects

The advent of pure organic thermally activated delayed fluorescence (TADF) emitters has transformed organic light emitting diodes (OLED) technology by enabling near 100% internal quantum efficiency without costly noble metals. TADF compounds achieve this by thermally converting triplet excitons to singlets via reverse intersystem crossing (RISC), aided by a small singlet-triplet energy gap (ΔEST). However, conventional donor–acceptor (D–A) TADF emitters suffer from poor color purity due to broad emission (FWHM above 70 nm), efficiency roll-off, and limited device lifetime, hindering commercial applications. The multi-resonance TADF (MR-TADF) strategy, addresses many of these limitations by embedding electron-donating (N, O) and electron-accepting (B) atoms within rigid polycyclic frameworks. This leads to localized frontier orbitals, narrow emission spectra (FWHM bellow 30 nm), and high PLQY. Yet, reported MR-TADF emitters largely emit in the blue region; efficient green and red emitters remain scarce, and issues of efficiency roll-off and operational stability persist. This proposal aims to design and develop next-generation MR-TADF emitters with emissions extending into the green and red regions, while enhancing device stability and efficiency. Two innovative molecular design strategies are proposed: Approach 1: Designing linearly extended B/N-based MR-TADF frameworks (27Cz36BCz and 36Cz27BCz) by functionalizing carbazole units. This is expected to enhance π-conjugation and achieve bathochromic shifts, enabling narrowband green and red emission while retaining rigidity for color purity. Approach 2: Introducing B-free MR-TADF emitters leveraging opposite resonance effects of carbazole nitrogen and pyridine nitrogen atoms (mCzPy and oCzPy). This design benefits from stronger C=N acceptor bonds (higher bond dissociation energy) to improve chemical robustness and device longevity. The project integrates computational studies to guide synthesis, followed by rigorous photophysical, electrochemical, and thermal characterization, thus highly interdisciplinary. The emitters performance will be validated in OLED devices to assess external quantum efficiency (EQE), roll-off, and operational stability. By pioneering these strategies, this research will overcome current limitations of MR-TADF materials, enabling energy-efficient, full-color OLEDs with superior color purity and durability, aligning with the demands of next-generation ultra high definition (UHD) displays and advanced optoelectronic applications.