Molecular doping plays a crucial role in modulating the
performance
of polymeric semiconductor (PSC) materials and devices. Despite the
development of numerous molecular dopants and doping methods over
the past few decades, achieving highly efficient doping of PSCs remains
challenging, primarily because of the inadequate matching of frontier
energy levels between the host polymers and the dopants, which is
critical for facilitating charge transfer. In this work, we introduce
a novel doping method termed photoexcitation-assisted molecular doping
(PE-MD), capable of transcending limitations imposed by energy level
disparities through the mediation of efficient photoinduced electron
transfer between polymers and dopants. This approach significantly
amplifies the electrical conductivity of the PDPP4T polymer, increasing
it by more than 4 orders of magnitude to a maximum value of 349.67
S cm–1. Given that only the irradiated region experiences
a substantial increase in doping level, the PE-MD process facilitates
the photoresist-free and precise patterning of doped polymers at a
resolution down to 1 μm. Furthermore, the enhanced electrical
conductivity of the photoexcitation-assisted molecularly doped PDPP4T
film promotes efficient thermoelectric conversion, yielding an impressive
initial power factor of 226.1 μW m–1 K–2 and a figure-of-merit (ZT) of 0.18,
accompanied by improved thermal and ambient stability. The PE-MD strategy
not only remarkably elevates the doping level of PSCs toward efficient
thermoelectric conversion but also preserves the easy processability
of flexible and integrated devices.