Laser‐Induced Local De‐Doping in Organic Semiconductors

This study explores control of the doping level in organic semiconductor films using scanning continuous wave laser radiation. The feasibility of this one-step non-contact post-deposition approach is explored for a benchmark material system comprising the high-mobility polymeric semiconductor PBTTT-C14 p-doped with the small-molecular acceptor F$_4$TCNQ. De-doping is achieved via laser-driven photothermal heating that induces neutralization and subsequent diffusion and/or sublimation of dopant molecules from the irradiated region. Comparison of 785 and 561 nm excitation, which are resonant with the absorption features of doped and neutral semiconductor, respectively, reveals that excitation at 785 nm leads to a less pronounced organic semiconductor degradation at comparable laser irradiance. Modulation of doping level is achieved with laser-resolution-limited feature sizes below 10 µm, with laser power adjustment enabling the tunability of electrical resistance by two and five orders of magnitude for excitation at 785 and 561 nm, respectively. This fully digital process is conducted in ambient atmosphere and does not require any additional equipment, therefore allowing straightforward integration with high-throughput mass-production of molecular electronics.