Highly efficient modulation of the electronic properties of organic semiconductors by surface doping with 2D molecular crystals

Doping is a critically important strategy to modulate the properties of organic semiconductors (OSCs) to improve their optoelectrical performances. Conventional bulk doping involves the incorporation of foreign molecular species (i.e., dopants) into the lattice of the host OSCs, and thus disrupts the packing of the host OSCs and induces structural defects, which tends to reduce the mobility and (or) the on/off ratio in organic field-effect transistors (OFETs). In this article, we report a highly efficient and highly controllable surface doping strategy utilizing 2D molecular crystals (2DMCs) as dopants to boost the mobility and to modulate the threshold voltage of OFETs. The amount of dopants, i.e., the thickness of the 2DMCs, is controlled at monolayer precision, enabling fine tuning of the electrical properties of the OSCs at unprecedented accuracy. As a result, a prominent increase of the average mobility from 1.31 to 4.71 cm(2) V(-1)s(-1) and a substantial reduction of the threshold voltage from -18.5 to -1.8 V are observed. Meanwhile, high on/off ratios of up to 10(8) are retained.