PHOTOCONDUCTIVE ZNO FILMS PRINTED ON FLEXI BLE SUBSTRATES BY INKJET AND AEROSOL JET TECHNIQUES

Zinc oxide (ZnO) thin films have remarkable versatility in sensor applications. Here, we report simple ink synthesis and printing methods to deposit ZnO photodetectors on a variety of flexible and transparent substrat.es, including polyimide (Kapton), polyethylene terephthalate, cyclic olefin copolymer (TOPAS), and quartz. X-ray diffraction analysis revealed the dependence of the film orientation on the substrate type and sintering method, and ultravioletvisible (UV-Vis) absorption measurements revealed a band edge near "80 nm. Van der Pauw technique was used to measure the resistivity of undoped ZnO and indium/gallium-codoped ZnO (IGZO) films. IGZO films showed lower resistivity and larger average grain size compared with undoped ZnO films due to addition of In3+ and Ga3+, which act as donors. A 365 nm light-emitting diode was used to photoirradiate the films to study their photoconductive response as a function of light intensity at 300 K. Experiments revealed that ZnO films printed by aerosol jet and inkjet techniques exhibited five orders of magnitude photoconductivity, indicating that such films are viable options for use in flexible photodetectors.