Room temperature detection of H2S by flexible gold–cobalt phthalocyanine heterojunction thin films

• Flexible Au–CoPc heterojunction films were synthesized on BOPET substrate.
• Au–CoPc films exhibit higher response for H2S as compared to pure CoPc films.
• The high hole charge carrier density at the Au–CoPc surface makes it more oxidative to the H2S.

We report an improved H2S response of flexible gold (Au)–cobalt phthalocyanine (CoPc) heterojunction thin films at room temperature. The Au–CoPc films exhibit very high charge carrier density at the surface due to (i) the difference in work function of Au and CoPc and (ii) enhanced adsorbed oxygen on the CoPc surface owing to spillover effect. Both of these effects make the Au–CoPc films more oxidative to the H2S in comparison to pure CoPc films. The response of the films on exposure to H2S is attributed to the shrinkage of the hole accumulation layer of CoPc due to electron transfer from adsorbed electron donor H2S. The gas sensing characteristics of the films were found to be stable for the bending radius >20 mm.