Pen plotter printing of ITO thin film as a highly CO sensitive component of a resistive gas sensor.

In2O3-10%SnO2 (ITO) thin films on various substrates have been obtained by pen plotter printing using a solution of hydrolytically active heteroligand complexes [M(C5H7O2)x(C4H9O)y] (where М = In3+ and Sn4+) as a functional ink. According to XRD and Raman spectroscopy, it has been established that the film has a bixbyite structure (space group Ia3/Th7), consists of particles with an average size of about 20 nm (according to SEM and AFM) and has a band gap of 3.57 eV. In order to obtain the ITO film, the temperature dependence of resistivity characterised by a minimum at 150 °C has been determined, and its gas-sensitive properties have been studied. It has been shown that the greatest resistive response is observed to carbon monoxide at 200 °C, and the film has a high sensitivity to low concentrations of CO. Two possible models describing the dependence of the sensory response on the CO concentration have been suggested. The mechanisms of defect formation in the ITO film structure and CO detection, including in a humid environment, have been considered in detail.

Acceptor-Enhanced Local Order in Conjugated Polymer Films.

Disorder in conjugated polymers is a general drawback that limits their use in organic electronics. We show that an archetypical conjugated polymer, MEH-PPV, enhances its local structural and electronic order upon addition of an electronic acceptor, trinitrofluorenone (TNF). First, acceptor addition in MEH-PPV results in a highly structured XRD pattern characteristic for semicrystalline conjugated polymers. Second, the surface roughness of the MEH-PPV films increases upon small acceptor addition, implying formation of crystalline nanodomains. Third, the low-frequency Raman features of the polymer are narrowed upon TNF addition and indicate decreased inhomogeneous broadening. Finally, the photoinduced absorption and surface photovoltage spectroscopy data show that photoexcited and dark polymer intragap electronic states assigned to deep defects disappear in the blend. We relate the enhanced order to formation of a charge-transfer complex between MEH-PPV and TNF in the electronic ground state. These findings may be of high importance to control structural properties as they demonstrate an approach to increasing the order of a conjugated polymer by using an acceptor additive.