Fig. 2: Photophysical properties of nDBTxPO and nDBTxPO:1% TMB.

Electronic absorption (Abs.), fluorescence (FL) and phosphorescence (PH) spectra in dilute dichloromethane (DCM), and photoluminescence (PL) and RTP/afterglow spectra of (a) nDBTxPO and (b) nDBTxPO:1% TMB. PH spectra in solution were measured at 77 K after a delay of 3 ms; RTP and afterglow spectra were recorded after a delay of 30 ms. All the emission spectra were measured with excitation at 280 nm. The energy levels of T_n^* and ³CT^* states were estimated according to edges of RTP and afterglow spectra, respectively; (c) Comparison on the different energy transfer processes in melt films of 28DBTDPO:1% TMB and 46DBTDPO:1% TMB, in which higher T_n^* energy level of 28DBTDPO matrix supports exothermal energy transfer to ⁿCT^* (n = 1 and 3 for singlet and triplet, respectively) energy levels of 28DBTDPO-TMB dipoles, on the contrary to endothermal energy transfer in the latter. d Excitation−emission spectral mapping of melt films based on nDBTxPO and nDBTxPO:1% TMB at room temperature. The correlations between the excitations of RTP and afterglow from neat and 1% TMB doped nDBTxPO films, respectively, are indicated by dash lines.