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

Here, this study successfully fabricates few-layer MoS₂ nanosheets from (NH₄)₂MoS₄ 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.

Patterned MoS₂ nanosheets obtained by rubbing/ion-beam treatment (RI-MoS₂) can efficiently function as hole transport layers and templates for alignment of an emissive layer {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)} with a nematic liquid crystal phase toward highly efficient polarized organic light-emitting diodes. Interestingly, the RI-MoS₂-based device exhibits an unprecedented average polarization ratio of 62.5:1 at the emitted wavelengths (166.7:1 at the peak intensity of 540 nm).

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