This manuscript reports the design, synthesis, and photophysical and electroluminescent properties of a rare example n-type emissive organic semiconductor.
This material is based on a dibenzothiophene sulfone end-capped with electron-withdrawing phthalimide units, resulting in an organic semiconductor with a low lowest unoccupied molecular orbital (LUMO) energy level of -4.07 eV.
Interestingly, this material exhibits a high photoluminescence quantum yield (PLQY) in solution of approximately 84%, which remains relatively high in solid state at around 30%.
The authors were able to prepare single crystals, which revealed an unusual growth direction along the short molecular axis, rather than along the π-π stacking direction, due to multiple weak hydrogen bonds. These single crystals were integrated into organic field effect transistor, and efficient n-type charge transport was evidenced, with electron mobility up to 0.17 cm² V⁻¹ s⁻¹.
Owing to the high luminescence properties of this material, the transistor devices exhibited electroluminescence with immobile emission zone in the unipolar mode with a moderate yet notable external quantum efficiency (EQE) of 0.24%

In my opinion, this work is well executed, original and relevant enough to warrant publication in J. Mater. Chem. C, and it could be accepted after very minor revisions, as detailed hereafter:

1) Figure 3a is not sufficiently clear. The resolution should be improved, or the Figure should be redrawn.

2) The .cif file of the structure should be provided as supplementary material.

3) In supporting information, in paragraph “1. Materials, Preparation and General Characterization Methods”, more details (or references) should be given concerning the OLET device fabrication and measurement:
- information about PMMA used (provider, molecular weight, …) and the thickness of the layer
- Method and equipment to evaluate the EQE

3) In supporting information, in paragraph “2. Synthesis”, the calculated and experimental values for the elemental analysis of DPIDBSO should be provided.

The authors have submitted a revised version of their manuscript and have adequately addressed my questions and comments.

I recommend this work for publication in Journal of Materials Chemistry C.