Free Charge Generation in Organic Photoconversion Devices–the Impact of Electrostatic Potentials

ABSTRACT The generation of free charges in organic semiconductors is fundamentally limited by the formation of tightly bound electron‐hole pairs (excitons) arising from their low dielectric screening. Conventional donor/acceptor (D/A) heterojunctions overcome this limitation through interfacial energetic offsets at the cost of high voltage losses that limit organic photoconversion device efficiency compared to inorganic counterparts. The success of non‐fullerene acceptors (NFAs), enabling efficient charge generation at relatively small energetic offsets, challenges this picture and suggests the need to consider additional charge generation mechanisms. In this review, we highlight the critical role of molecular electrostatic potentials in free charge generation within organic semiconductors. The molecular origins of electrostatic potentials are discussed within the multipole expansion framework, with particular emphasis on quadrupole moments arising from anisotropic charge distributions within a molecule. The role of these electrostatic effects in modulating interfacial energetics, inducing band bending, and facilitating charge separation in donor/acceptor heterojunctions is examined, alongside their extension to single‐component systems. In single‐component systems, orientation‐dependent molecular packing creates functional energetic offsets without the need for distinct donor and acceptor materials. Based on these observations, key molecular and device design strategies for harnessing electrostatic effects in next‐generation organic photoconversion devices are outlined.