Parametric Studies of Pulsed Nd:YAG Laser Deposition of ITO for OLED Application

Abstract

Device-quality ITO by pulsed Nd:YAG laser, successfully used for Organic Light Emitting Device (OLED), was deposited at room temperature and 250 o C. Although the optical transmittance of > 90% is achieved in the visible range, the ITO film resistivity is too high to enable an efficient OLED, as compared to that reported for KrF laser deposited ITO. At 250 and laser wavelength of 355 nm, the ITO film resistivity decreased by 10x to 2 × 10 -4Ωcm while its optical transmittance was > 90 %. For PET, the heating temperature was limited to o C and hence the ITO resistivity could only be decreased by a factor of 2 to 5 × 10 -4Ωcm. The thermally induced crystallization of ITO, which has a preferred <111> directional orientation texture, largely accounts for lowering of its film resistivity. The OLED was based on simple device structure of ITO/(PVK+TPD+Alq 3 )/Al, which output brightness was compared to that fabricated on the commercial ITO. Effet of an ultra-thin diamond-like carbon (DLC) layer in the OLED was investigated.

Pulsed Laser Deposition of ITO: From Films to Nanostructures

“…ITO films deposited by laser ablation of ITO target have been applied in various applications such as solar cell [7,31,32], organic light-emitting devices [4,12,26], and more recently as low loss alternative plasmonic materials in the near-infrared region [33]. Our results show that ITO films with a range of properties can be obtained, controlled by the deposition parameters.…”

“…A larger difference is observed for 193/248 nm deposition of ITO as compared to 355 nm deposition at room temperature. The resistivity that can be obtained by 193/248 nm laser is in the range of 10 −4 Ω cm, while optimization in terms of ITO doping concentration [24] or substrate temperature [4,26,29] is needed in order to achieve the resistivity in the same range for 355 nm laser deposition.…”

“…In addition to the formation of a uniform film, substrate temperature affects the carrier density of the films and thus the resistivity of the ITO films. Figure 3 shows the resistivity and the Hall effects measurement results of ITO films deposited by 248 nm [12] and a 355 nm laser [26]. As the substrate temperature was changed from room temperature (RT) to 300°C, the carrier density was doubled for the ITO films deposited by using 248 nm laser, while it was increased by 14 times for ITO deposited by using the 355 nm laser.…”

“…The crystallinity of ITO films is also affected by substrate heating during the deposition process. The ITO films [12] and (b) 355 nm laser [26].…”

“…Effects of substrate temperature on film resistivity, carrier density, and Hall mobility deposited by (a) 248 nm laser at 10 mTorr[12] and (b) 355 nm laser at 30 mTorr[26].…”