Effect of film thickness on the properties of indium tin oxide thin film grown by pulsed-laser deposition for organic light-emitting diodes

Abstract

Transparent conducting indium tin oxide (ITO) thin films were grown by pulsed laser deposition (PLD) on glass substrates. The structural, electrical and optical properties of these films were investigated as a function of film thickness (300 - 8700 A). Films were deposited using a KrF excimer laser (248nm, 30 ns FWHM) at a fluence of 2 J/cm 2 , at substrate temperature of 300 °C and 10 mTorr of oxygen pressure. For ITO films (500 - 4000 A thickness) deposited at 300 °C in 10 mTorr of oxygen pressure, the resistivity of 2 - 4 x 10 -4 Ω-cm was observed and the average transmission in the visible range (400 -700 nm) was about 85 - 90 %. The Hall mobility and carrier density for ITO films (500 - 4000 A thickness) were observed to be in the range of 24 - 27 cm 2 /V-s and 5 - 9 x 10 20 cm -3 , respectively. We have used the ITO thin films, deposited by PLD on silica substrates, as the anode contact in organic light emitting devices and studied the effect of ITO film thickness on the device performance. The optimum thickness of the ITO anode for the maximum device efficiency was observed to be about 500-1000 A. The device showed an external quantum efficiency of about 0.8 % at 100 A/m 2 .