Photocurrent generation in carbon nitride and carbon nitride/conjugated polymer composites.

The semiconductor and photovoltaic properties of carbon nitride (CNx) thin films prepared using a reactive magnetron cathodic sputtering technique were investigated both individually and as composites with an organic conjugated polymer, poly(2,2′-bithiophene) (PBT). The CNx films showed an increasing thickness as the deposition power and/or nitrogen content in the gas mixture increase. At low nitrogen content and low deposition power (25–50 W), the film structure was dominated by the abundance of the graphitic sp2 regions, whereas at higher nitrogen contents and magnetron power CNx films started to demonstrate semiconductor properties, as evidenced by the occurrence of photoconductivity and the development of a space charge region. However, CNx films alone did not show any reproducible photovoltaic properties. The situation changed, however, when CNx was deposited onto conjugated PBT substrates. In this configuration, CNx was found to function as an acceptor material improving the photocurrent generation ...