Triple-stacked hole-selective layers for efficient solution-processable organic semiconducting devices

We report on an investigation of water-processable triple-stacked hole-selective layers for solution-processable organic semiconducting devices using a simple horizontal-dip (H-dip) coating technique. Homogeneous layers were successfully deposited via H-dip-coating using aqueous solutions of graphene oxide (GO), molybdenum oxide (MoO3), and poly(ethylenedioxy thiophene):poly(styrene sulfonate) (PEDOT:PSS). The use of the triple-stacked GO/MoO3/PEDOT:PSS layers as hole-injecting layers (HILs) in solution-processable organic light-emitting diodes (OLEDs) resulted in a considerable improvement of device performance in terms of brightness (maximum brightness: 47,000 cd/m2) as well as efficiency (peak efficiency: 31.5 cd/A), exceeding those of an OLED with a conventional single PEDOT:PSS HIL. Furthermore, polymer solar cells (PSCs) with these triple-stacked layers used as hole-collecting layers (HCLs) showed a considerable improvement in power conversion efficiency (6.62%), which was also higher than that (5.65%) obtained using the single PEDOT:PSS HCL. These results clearly indicate the benefits of using triple-stacked GO/MoO3/PEDOT:PSS layers, which provide better hole-injection/collection, electron-blocking, and improved stability for high performance solution-processable OLEDs and PSCs.