Kritam Thapa | Searcharxiv

arXiv2025

A High Throughput Virtual Screening Approach for Identifying Thermally Activated Delayed Fluorescence-Based Emitters

Thermally activated delayed fluorescence (TADF) offers the promise of highly efficient organic light emitting diodes (OLEDs), without the heavy metals requirement of the previous generation of OLEDs. However, the design of new TADF emitters is complicated by competing requirements, which require opposing design strategies. High throughput virtual screening (HTVS) approaches, however, offer the possibility of identifying new TADF emitters without necessarily relying on existing design rules. In this work the STONED algorithm [A. Nigam et al., Chem. Sci., 2021, 12, 7079] is used to impose random structural mutations starting from a set of twenty parent molecules, composed of both traditional donor-acceptor and multiresonant TADF emitters. Following this, successive filters are applied based on features of the atomic structure through to time-dependent density functional theory calculations. Although the randomised approach proves to be ill-suited to rediscovering existing TADF emitters, the resulting workflow leads to the identification of a number of molecules with promising properties for TADF, across a range of emission colours.

physics.chem-ph↗

arXiv2022

Transition-Based Constrained DFT for the Robust and Reliable Treatment of Excitations in Supramolecular Systems

Despite the variety of available computational approaches, state-of-the-art methods for calculating excitation energies such as time-dependent density functional theory (TDDFT), are computationally demanding and thus limited to moderate system sizes. Here, we introduce a new variation of constrained DFT (CDFT), wherein the constraint corresponds to a particular transition (T), or combination of transitions, between occupied and virtual orbitals, rather than a region of the simulation space as in traditional CDFT. We compare T-CDFT with TDDFT and $Δ$SCF results for the low lying excited states (S$_{1}$ and T$_{1}$) of a set of gas phase acene molecules and OLED emitters, as well as with reference results from the literature. At the PBE level of theory, T-CDFT outperforms $Δ$SCF for both classes of molecules, while also proving to be more robust. For the local excitations seen in the acenes, T-CDFT and TDDFT perform equally well. For the charge-transfer (CT)-like excitations seen in the OLED molecules, T-CDFT also performs well, in contrast to the severe energy underestimation seen with TDDFT. In other words, T-CDFT is equally applicable to both local excitations and CT states, providing more reliable excitation energies at a much lower computational cost than TDDFT. T-CDFT is designed for large systems and has been implemented in the linear scaling BigDFT code. It is therefore ideally suited for exploring the effects of explicit environments on excitation energies, paving the way for future simulations of excited states in complex realistic morphologies, such as those which occur in OLED materials.

physics.chem-ph↗