Hydrogen-Bond Identity as an Electronic Design Parameter in Diketopyrrolopyrrole Semiconductors

Hydrogen-bonding is widely used in organic semiconductors as a supramolecular tool to control molecular packing and thin-film morphology. Amide and urea groups are among the most common hydrogen-bonding moieties employed for this purpose and are often treated as interchangeable units, despite their well‐known differences in hydrogen‐bond strength and directionality. Nevertheless, their specific impact on the electronic properties of small-molecule organic semiconductors remains poorly understood. Here, we demonstrate that hydrogen-bond identity plays an active and decisive role in the electronic properties of small-molecule semiconductors. Two thiophene-flanked diketopyrrolopyrrole derivatives functionalized with either amide or urea groups were designed to isolate the effect of hydrogen-bonding while preserving an identical π-conjugated backbone. While both materials exhibit nearly indistinguishable optical and electronic properties in solution, marked differences arise in the solid state. Spectroscopic analyses reveal that hydrogen-bonding directly modulates conjugation pathways and charge stabilization, rather than acting solely as a structural organizing element. Notably, despite forming stronger and more directional hydrogen-bonding networks, the urea-functionalized semiconductor shows reduced charge stabilization and inferior field-effect mobility compared to its amide analogue. These results demonstrate that stronger hydrogen-bonding does not necessarily enhance charge transport and establish hydrogen-bond identity as a critical electronic design parameter in organic semiconductors.