A Fused Diketopyrrolopyrrole Derivative for Single-Crystal Visible-NIR Organic Phototransistor

Organic phototransistors (OPTs) have garnered significant attention due to their potential in wearable and flexible electronics. However, achieving high carrier mobility and broadband response in organic semiconductors for OPTs remains a challenge. In this work, a new fused diketopyrrolopyrrole (FDPP) derivative is reported, 2,9-bis(4-hexylphenyl)-7H,14H-thieno[3',2':7,8]indolizino[2,1-a]thieno[3,2-g]indolizine-7,14-dione (FDPP-p-C6), synthesized through N-cyclization of DPP with an adjacent thiophene unit. This N-cyclization ensures backbone planarity, while the hexyl side chains remain distant from the fused core, minimizing steric hindrance and promoting efficient intermolecular stacking. Consequently, single crystals of FDPP-p-C6 exhibit a planar backbone and a typical herringbone packing arrangement, facilitating charge transport. The single-crystal organic field-effect transistors (OFETs) demonstrate p-type charge transport, achieving maximum mobility of 0.20 cm² V^-¹ s^-¹. Additionally, the single-crystal OPTs show promising performance, with high responsivity across a broad spectral range and a photoresponsivity of 2.2 × 10³ A W^-¹ along with a specific detectivity, derived from the noise current, of 2.8 × 10¹⁰ Jones. This study highlights the potential of FDPP as a key material for advancing single-crystal OFET and OPT technologies, propelling relevant research forward.