Microwave-assisted synthesis of sponge-like carbon nanotube arrays and their application in organic transistor devices

Multi wall carbon nanotube (MWNT) sponges were synthesized with a domestic microwave oven. The procedure involves a mixture of graphite and cobalt acetate powders enclosed in an evacuated quartz ampoule exposed to microwave irradiation. Maximum yield of MWNT sponges of about 2.2 cm² is obtained within 12 min of microwave exposure with individual MWNTs having diameters in the 20–50 nm range. Employing MWNT obtained from synthesized sponges we construct two types of organic transistors: a field effect OFET device in which the channel material is a MEH-PPV semiconducting polymer blended with the synthesized MWNT, and a light emitting transistor OLET device in which electrodes are prepared with MWNT, the channel material being the MEH-PPV polymer alone. These devices are characterized with I–V measurements. For the OFET device the I_on/I_off figure is considerably improved by using the polymer/MWNT blend as channel. In the OLET device, I–V characteristics with MWNT electrodes are comparable to those obtained when ITO electrodes are used.