Polarized Light-Emitting Diodes Based on Patterned MoS2 Nanosheet Hole Transport Layer.

Here, this study successfully fabricates few-layer MoS2 nanosheets from (NH4 )2 MoS4 and applies them as the hole transport layer as well as the template for highly polarized organic light-emitting diodes (OLEDs). The obtained material consists of polycrystalline MoS2 nanosheets with thicknesses of 2 nm. The MoS2 nanosheets are patterned by rubbing/ion-beam treatment. The Raman spectra shows that {poly(9,9-dioctylfluorene-alt-benzothiadiazole), poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)]} (F8BT) on patterned MoS2 exhibits distinctive polarization behavior. It is discovered that patterned MoS2 not only improves the device efficiency but also changes the polarization behavior of the devices owing to the alignment of F8BT. This work demonstrates a highly efficient polarized OLED with a polarization ratio of 62.5:1 in the emission spectrum (166.7:1 at the peak intensity of 540 nm), which meets the manufacturing requirement. In addition, the use of patterned MoS2 nanosheets not only tunes the polarization of the OLEDs but also dramatically improves the device performance as compared with that of devices using untreated MoS2 .