Organic field-effect transistors suffer from ultra-high operating voltages in addition to their relative low mobility. A general approach to low-operating-voltage organic field-effect transistors (OFETs) using donor/acceptor buffer layers is demonstrated. P-type OFETs with acceptor molecule buffer layers show reduced operating voltages (from 60-100 V to 10-20 V), with mobility up to 0.19 cm(2) V-1 s(-1) and an on/off ratio of 3 x 10(6). The subthreshold slopes of the devices are greatly reduced from 5-12 V/decade to 1.68-3 V/decade. This favorable combination of properties means that such OFETs can be operated successfully at voltages below 20 V (vertical bar V-DS vertical bar <= 20 V, vertical bar V-GS vertical bar <= 20 V ). This method also works for n-type semiconductors. The reduced operating voltage and low pinch-off voltage contribute to the improved ordering of the polycrystalline films, reduced grain boundary resistance, and steeper subthreshold slopes.