Solution-processed hybrid p–n junction vertical diode

Solution-processed n-ZnO/p-poly(3,3′′′-didodecylquaterthiophene) (PQT-12) vertical p–n junction diodes were prepared on ITO-coated glass. A continuous film of ZnO nanoparticles was grown on the ITO glass by dip-coating and subsequent heat treatment of a zinc acetate film. PQT-12 was then spin-coated to form the ZnO/PQT-12 diode. Gold was chosen as the top electrode to complement ITO for this diode. The microstructures of ZnO films are studied by atomic force microscopy (AFM) and show a continuous, dense layer of ZnO nanoparticles. The current–voltage (I–V) measurement shows that the maximum current density for this p–n junction diode is 400 A/cm2, which is much higher than previously reported polymer diodes. Capacitance–voltage (C–V) data also provide evidence of formation of the p–n junction. The rectification was characterized by observation of full input-half output waves. Data indicate that these devices can operate up to frequencies of 14 MHz under ambient environment conditions. This rectification frequency is higher than other reported polymer Schottky diodes under these conditions. Turnon voltages of this diode are also much lower than for the reported polymer diodes.