Printable biflourene based ultra-violet (UV) organic light-emitting electrochemical cells (OLECs) with improved device performance

Abstract

A series of printable UV emitting ionic bifluorene derivatives have been prepared incorporating pendent alkylimidazolium groups. Herein, we detail the synthesis of compounds and the methods used in device fabrication. We show how ink formulation is improved by increasing the solubility of the active bifluorene through extension of the alkyl chain length and switching the counter ion from PF 6 − to CF 3 SO 3 − . We also show how organic light emitting electrochemical cells (OLECs) can be fabricated by spray coating to achieve an active layer with a thickness of ∼150–200 nm, leading to working devices with a turn on voltage of around 6.5 V. This gives electroluminescent (EL) that peaks between 385 nm and 390 nm with a maximum EL emission intensity of 1.29 μW/cm 2 . Thus, EL emission within the UV range has been demonstrated successfully with the synthesised molecules via spray coating onto glass slides. UV light emitting ionic bifluorene small molecules have been synthesised and used to fabricate the OLECs on ITO glass slides. Spray coating technique has been utilized to deposit the functional layers in the OLECs. While the OLEC light emission layer is optimized to the thickness of ∼250 nm, the encapsulated devices demonstrated the turn on voltage of 6.5 V. This fabrication process can be adopted to achieve the light emitting textiles.