Highly efficient and stable quantum dot light-emitting devices with a low-temperature tin oxide electron transport layer

Abstract

Solution processed metal oxides with the characteristics of low cost, high mobility and good transparency are promising materials for the carrier transport layer of optoelectronic devices. So far, solar cells with tin oxide (SnO₂) transport layers have been demonstrated to achieve high efficiency and long-term stability. However, it is still a challenge to achieve highly efficient and long-term stable quantum dot light-emitting devices (QLEDs) with SnO₂. Here, we prepared QLEDs with a low-temperature SnO₂ electron transport layer (ETL), and found that the residual hydroxyl group (–OH) seriously degenerates the operating lifetime of the QLEDs. UV-Ozone treatment (UVO) is then proposed to decompose the residual tin hydroxide into stoichiometric SnO₂. Compared with the control QLEDs with SnO₂ without UVO, the QLEDs with UVO SnO₂ possess the same efficiency, but show a nearly two times higher operating lifetime. With an initial luminance of 500 cd m⁻², the QLEDs with UVO SnO₂ show a half-luminance operating time of 2168 h, while that of the control device is only 1015 h.