A model Hamiltonian map for organic semiconductor doping regimes

Molecular doping of organic semiconductors (OSCs) depends on coupled energetic and electronic parameters that control integer charge transfer, charge-transfer complex formation, and double doping. Here, we use exact diagonalization of a coarse-grained Pariser-Parr-Pople-style Hamiltonian to map OSC doping regimes across molecularly tunable parameters: the OSC-dopant energy offset, on-site Hubbard repulsions, intermolecular electronic couplings, and inter-site Coulomb interactions. Minimal two-site, three-site, and extended OSC-aggregate models show that Hubbard repulsion is essential for stabilizing single-polaron states, suppressing bipolaron formation, and enabling double-doped states with charge delocalized across OSC aggregates. In contrast, strong OSC-dopant electronic coupling promotes partial charge-transfer-complex character, while strong OSC-OSC coupling and weak Coulomb binding favor delocalized integer-charge carriers. These results provide a compact theoretical framework for rationalizing and designing OSC-dopant pairs with targeted charge-transfer character and doping efficiency.