Cocrystal engineering: towards high-performance near-infrared organic phototransistors based on donor-acceptor charge transfer cocrystals

Near-infrared organic phototransistors have wide application prospects in many fields. The active materials with the high mobility and near-infrared response are critical to building high-performance near-infrared organic phototransistors, which are scarce at present. Herein, a new charge transfer cocrystal using 5,7-dihydroindolo[2,3-b]carbazole (5,7-ICZ) as the donor and 2,2′-(benzo[1,2-b:4,5-b′]dithiophene-4,8-diylidene)dimalononitrile (DTTCNQ) as the acceptor is properly designed and prepared in a stoichiometric ratio (D:A=1:1), which not only displays a high electron mobility of 0.15 cm2 V−1 s−1 and very low dark current, but also can serve as the active layer materials in the region of near-infrared detection due to the narrowed band gap and good charge transport properties. A high photosensitivity of 1.8×104, the ultrahigh photoresponsivity of 2,923 A W−1 and the high detectivity of 4.26×1011 Jones of the organic near-infrared phototransistors are obtained.