In solid-state, all derivatives display fluorescence emission, and their PLQY is enhanced compared to the diluted solution (Fig. and Table ). The emissions wavelengths are blue-shifted compared to the solution, with a maximum centered 556 nm instead of 578 nm for 2a and 610 nm instead of 637 nm for 2b. 2a even shows a PLQY of 1 in solid-state instead of 0,34 in solution. Interestingly, this value measured in solid-state is higher than the corresponding value of the analog molecule with an exocyclic phenyl moiety (PLQY = 0,68) instead of ethoxy. Erreur ! Signet non défini. It is clear that the modification of the phosphorus center can enhance the PLQY. 2b displays a PLQY of 0,65 in solid-state, much higher than in solution (0,09). Interestingly, 2c, which was not luminescent in solution, displays solid-state emission with a PLQY of 0,14. This enhancement of the emission in solid-state is known for related benzophosphole derivatives whose Aggregation-Induced Emission (AIE) properties were already reported. Fluorescence lifetimes () of these emitters were measured at room temperature on the solid-state samples (Fig. and Table ). All those emitters display a biexponential decay in the nanosecond range, typical of fluorescence. This is in marked contrast with the TADF behavior observed with dibenzophospholes oxides substituted with similar amino groups, highlighting the strong differences between the benzophosphole and the dibenzophosphole cores. Radiative (kr) and non-radiative (knr) constants of those fluorophores have been calculated using their PLQY and the lifetime of their most contributive component. 2a has a kr of 13.1x10 7 s -1 and no accurate value of knr can be given as the PLQY reaches 1. 2b displays a kr of 16.9x10 7 s -1 even higher than 2a, but a lower PLQY (0,65) due to the appearance of a non-trifling knr of 9.1x10 7 s -1 reflecting the energy gap law. 2c displays a low kr value (2.7x10 7 s -1 ), consistent with a small oscillator strength for the transition due to the poor conjugation between donor and acceptor driven by the twisted conformation of the phenoxazine group, as well as a large knr value (16.8x10 7 s -1 ). a In DCM (10 -5 M). b calculated relative to fluorescein (NaOH, 0.1 M), ref= 0.79. Measured in calibrated integration sphere d kr = radiative relaxation rate (kr = ); knr = non-radiative relaxation rate (knr = (1-)/). Only the most contributive radiative constant was taking in account for the calculation.