Research Projects

The global optoelectronic market is experiencing significant growth aiming to reach 70 billion dollars by 2030. To place India at the forefront of optoelectronic research, we need to develop new technologies and materials and gain control over their performance. Design and development of light emitting devices has received widespread attention in the field. However the challenge is to make cheaper and energy efficient display technologies that consume minimal power. OLED (Organic Light-Emitting Diode) has revolutionised display technology, largely due to its ability to produce true blacks, high contrast, and vibrant colors. The key concept in OLED is electrical excitation that creates excitons (electron-hole pairs) in two forms: emissive singlets and nonemissive triplets in 1:3 ratio. However, both the singlet and triplets need to be harnessed to improve the emission efficiency of devices. Thermally activated delayed fluorescence (TADF) is a promising innovation in OLED technology where these nonemissive triplet excitons can be converted back into emissive singlet excitons through reverse intersystem crossing (rISC). Therefore TADF materials utilise both singlet and triplet excitons for light emission and enable nearly 100% internal quantum efficiency. Efficient exciton formation and control over singlet-triplet conversion is key to TADF performance. The state-of-the-art OLED device consists of TADF materials (guest) embedded into a host matrix which minimises concentration quenching of TADF excitons and facilitate exciton and charge mobilites for achieving high brightness, better color purity, and long operational lifetimes. Environmental factors such as polarity and viscosity has been reported to massively affect the rISC timescale and TADF emission. Therefore the host materials must be carefully selected to ensure optimal dielectric and viscous properties that can facilitate efficient TADF emission by minimising non-radiative losses. However tuning microenvironments in TADF-based OLED devices is relatively neglected aspect. Infact recently it has been realised that intramolecular hydrogen-bonding is important in maintaining rigid conformation, reducing nonradiative losses and improving TADF emission. Though the environmental parameters that affect such H-bonding have never been explored. Here I will perform a systematic and detailed investigation on the role of environment in TADF emission using a range of solvents with different polarity, viscosity and H-bonding ability and probing through optical spectroscopic tools. The fundamental knowledge thus obtained will be utilised to tune microenvironment of TADF films through using different additives. The right environment will significantly boost the TADF emission and help in achieving energy-efficient display devices. Finally OLED device will be fabricated based on such efficient materials and will be commercialised for real-world application.