Molecular insights into balanced hole and electron transport in urea-modified fluorene for OLED applications

The optoelectronic and charge-transport characteristics of fluorene (F) and its urea derivative, N-(9H-fluoren-9-yl) urea (9FU), are investigated in this work using DFT and TD-DFT. Electronic excitations, charge extraction parameters, ionisation potentials, electron affinities, and reorganisation energies were all methodically examined. The findings demonstrate that urea substitution at fluorene's 9-position increases charge-transfer balance and electron magnetism, allowing for ambipolar behaviour. 9FU has better charge-transport and excitation properties than fluorene, suggesting that it could be used in effective OLED applications. • High conjugation and planarity in F and 9FU enable efficient charge transport. • Urea substitution causes a strong red shift, enhancing ICT behaviour. • Excitation analysis shows a shift from local transitions (F) to ICT-dominated in 9FU. • Optoelectronic improvements make 9FU a strong OLED candidate.