The Role of Local Triplet Excited States and D‐A Relative Orientation in Thermally Activated Delayed Fluorescence: Photophysics and Devices

Here, a comprehensive photophysical investigation of a the emitter molecule DPTZ‐DBTO2 , showing thermally activated delayed fluorescence (TADF), with near‐orthogonal electron donor (D) and acceptor (A) units is reported. It is shown that DPTZ‐DBTO2 has minimal singlet–triplet energy splitting due to its near‐rigid molecular geometry. However, the electronic coupling between the local triplet ( 3 LE) and the charge transfer states, singlet and triplet, ( 1 CT, 3 CT), and the effect of dynamic rocking of the D–A units about the orthogonal geometry are crucial for efficient TADF to be achieved. In solvents with low polarity, the guest emissive singlet 1 CT state couples directly to the near‐degenerate 3 LE,…

• UO
  University of Oxford
• CD
  Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

  Awards: BEX9474-13-7, BEX9474‐13‐7
• ME
  Ministerstwo Edukacji i Nauki
• EA
  Engineering and Physical Sciences Research Council

  Awards: EP/I006656/1, EP/L02621X/1, EP/L02621X/1, EP/K016164/1