Influence of Ga-doped transparent conducting ZnO thin film for efficiency enhancement in organic light-emitting diode applications

Abstract

In this paper, transparent conducting n-type ZnO:Ga and commercially available SnO $$_2$$ :F (U-type Asahi) thin films have been used as a front electrode (Anode) in organic light-emitting diode (OLED)-based display devices. RF magnetron sputtered ZnO:Ga thin films with an electrical resistivity of 9.6 $$\times $$ 10 $$ ^{-5} $$ $$\varOmega -cm$$ , low sheet resistance less than 5.6 $$\varOmega $$ / $$\square $$ and optical transparency greater than 90% have been reported at room temperature (RT) using the glass substrate. The OLED device structure consists of transparent conducting oxide (TCO) (170 nm)/HAT-CN (15 nm)/TAPC (30 nm)/CBP:Ir(ppy) $$ _{3} $$ (30nm; 8wt%)/BPhen(50 nm)/LiF (1 nm)/Al (120 nm). Normalized intensity of both types TCO (ZnO:Ga and SnO $$_2$$ :F)-based OLED shows a similar kind of result. The results suggest that Ga-doped ZnO thin films are the substitutional anode materials of commercially established SnO $$_2$$ :F (fluorine-doped tin oxide), ITO (tin-doped indium oxide) for the OLED application, and also in other optoelectronic devices. The important figures of merit such as external quantum efficiency, current and power efficiency of ZnO:Ga (GZO)-based OLED are demonstrated and compared with SnO $$_2$$ :F (FTO)-based OLED. These results suggest that Ga-doped ZnO thin films can be a promising candidate as the anode layer in OLEDs as a substitution to ITO and SnO $$_2$$ :F film.