Flexible and Transparent Electrodes of Cu2−XSe with Charge Transport via Direct Tunneling Effect

In this paper, it is demonstrated that copper selenide (Cu2−XSe) films onto polyester sheets may serve as transparent electrodes in inorganic–organic hybrid light emission devices (IOHLED), as possible replacement to indium tin oxide or fluorine‐doped tin oxide. The Cu2−XSe film synthesized via bath chemical deposition is electrically stable with a sheet resistance of 148 Ω sq−1 and optical bandgap of 2.3 eV. IOHLED are made with poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) as an organic layer for hole transport and poly[2‐metoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV) as electroluminescent semiconductor. The IOHLED emits in the visible range owing to the simultaneous emission from Cu2−XSe and MEH‐PPV layers. The enhanced performance is explained by analyzing the charge transport mechanisms at the inorganic–organic interface, which for Cu2−XSe/PEDOT:PSS changes from Fowler‐Nordheim to direct tunneling regardless of the device temperature (90–370 K). The onset voltage is 75% smaller than in the absence of the PEDOT:PSS layer due to a 27 meV decrease in the potential barrier, and the direct tunneling becomes more relevant to device performance than the sheet resistance of the Cu2−XSe layer. Upon adding transparency, mechanical flexibility, and covering large areas, the ultrathin Cu2−XSe films on polyester substrates permit new designs for electro‐optical devices with inorganic–organic heterojunctions. Charge transport via direct tunneling in inorganic–organic semiconductor interface in hybrid light emission diodes using transparent and flexible polyester/copper selenide (Cu2−XSe) films. is presented.