Realization of polymer charge pump circuits using polymer semiconductors

Vertical diodes made of chromium/gold/poly(3-hexylthiophene) (P3HT)/aluminum are used to implement AC-DC charge pump circuits. A single stage polymer charge pump with 470 nF capacitors is able to supply 7.2 V DC to a load of 1 M Omega || 20 pF when an AC signal with a peak value of 10 V is applied. The circuit can be used up to 10 kHz. High turn-on voltages and internal resistances and capacitances of the diodes limit the DC output voltages. The ramp-up time of the circuit built with 10 nF capacitors is 9.4 ms for a 1 kHz, 10 V peak AC signal. Diodes are modeled and simulated in SPICE using space charge limited conduction model. The simulated charge pump circuit produces consistent results with measurements. Performances of air exposed vertical diodes deteriorate under vacuum, prolonged operation at atmospheric conditions and electrical bias stress resulting in blistering, emphasizing the importance of packaging the devices under inert atmosphere. The DC output voltage and the input impedance of the circuit can be adjusted by using multiple stages. (C) 2010 Elsevier B.V. All rights reserved.