Transparent conducting indium tin oxide thin film grown on flexible substrate by pulsed-laser deposition for organic light-emitting devices

Abstract

Transparent conducting indium tin oxide (ITO) thin films were grown by pulsed laser deposition (PLD) on glass and on flexible polyethylene teraphthalate (PET) substrates. The structural, electrical and optical properties of these films were investigated as a function of substrate deposition temperature and background gas pressure. Films were deposited using a KrF excimer laser (248 nm, 30 ns FWHM) at a fluence of 1.2 J/cm<SUP>2</SUP>. Films were deposited at substrate temperatures ranging from 25 degree(s)C to 150 degree(s)C in oxygen pressures ranging from 10 to 60 mTorr. ITO films (280 nm thick), deposited by PLD on PET at 25 degree(s)C and 45 mTorr of oxygen, exhibit a low electrical sheet resistance (20 - 25 (Omega) /sq.) and high transparency (approximately 85%) in the visible range (400-700 nm). We have also used the ITO thin films deposited on both glass and PET substrates by PLD as the anode contact in organic light emitting devices (OLEDs) and measured the device performance. The external quantum efficiency measured at a current density of 250 A/m<SUP>2</SUP> for the device on PET was approximately 0.9%, which is higher than that (approximately 0.5%) for the device on glass. The reduction in the driving voltage and high external quantum efficiency made an ITO coated PET substrate very promising for future large scale OLED application.