Laser sintering of gravure printed indium tin oxide films on polyethylene terephthalate for flexible electronics

Abstract

Tin doped indium oxide (ITO) thin films provide excellent transparency and conductivity for electrodes in displays and photovoltaic systems. Current advances in producing printable ITO inks are reducing the volume of wasted indium during thin film patterning. However, their applicability to flexible electronics is hindered by the need for high temperature processing that results in damage to conventional polymer substrates. Here, we detail the conditions under which laser heating can be used as a replacement for oven and furnace treatments. Measurements of the optical properties of both the printed ITO film and the polymer substrate (polyethylene terephthalate, PET) identify that in the 1.5–2.0 μm wavelength band there is absorption in the ITO film but good transparency in PET. Hence, laser light that is not absorbed in the film does not go on to add a deleterious energy loading to the substrate. Localization of the energy deposition in the film is further enhanced by using ultrashort laser pulses (~1 ps) thus limiting heat flow during the interaction. Under these conditions, laser processing of the printed ITO films results in an improvement of the conductivity without damage to the PET.

The Influence of Film and Storage on the Phenolic and Antioxidant Properties of Red Raspberries (Rubus idaeus L.) cv. Erika

“…Polyethylene terephthalate (PET) is one of the most widely used films for packaging of foods. It is flexible, has extremely low electrical-resistance, has a good transparency, and an extremely high transparent electromagnetic interference shielding [19], minimizing the heat conduction during laser irradiation [20], and it is easy to find.…”

Additive Manufacturable Materials for Electrochemical Biosensor Electrodes

“…used SLS to form tin‐doped indium oxide thin films on a PET substrate. [ 303 ] Their approach precluded the need for high temperature sintering that would otherwise damage PET. Zacharatos et al.…”

Inkjet‐Printed Conductive ITO Patterns for Transparent Security Systems

“…[ 10 ] One practical advantage of ink‐based processes is the possibility of direct patterning of ITO structures, which can be achieved by digital printing of ITO‐containing inks. Thus, ITO patterns have been prepared by inkjet [ 11–17 ] or gravure printing [ 18–20 ] endowing fast, simple, and high‐throughput printable optoelectronics. [ 19–23 ] Inkjet‐printed NPs‐based ITO films have demonstrated resistivity values on the order of 10 −2 Ω cm; however, they required postdeposition annealing at the temperatures higher than 300 °C for about 6 h. [ 19 ] This makes them incompatible with many intended low‐temperature device stacks and temperature‐sensitive substrates.…”

“…Important electrical parameters of the fabricated ITO layers are also summarized in Table S1 (Supporting Information). The annealing temperature for the gravure printed ITO layers was as low as 70 °C; [ 18 ] however, the resistivity of the samples was only 1.2 × 10 −2 Ω cm. The previously reported inkjet‐printed ITO layers required annealing temperatures higher than 300 °C, and their electrical resistivity could not be lowered below 10 −2 Ω cm [ 11–17 ] (Figure 3f).…”