Surface Passivation of the Cu2–xSe Electrode During the Chemical Bath Deposition

Herein, p ‐type flexible and transparent electrodes of Cu 2– x Se are produced at different conversion times at 20, 25, and 30 s of polyester/Cu thin films via chemical bath deposition. To study the charge transport properties across the Cu 2– x Se layer, the organic light‐emitting diodes (OLEDs) are produced according to the following configuration: polyester/Cu 2– x Se/poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate)/poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene]/aluminum (polyester/Cu 2– x Se/PEDOT:PSS/MEH‐PPV/Al), resulting in a direct tunneling in the transport of holes. The control of the barrier's energy between the Cu 2– x Se electrode and the MEH‐PPV polymer allows it to tune selectively of the OLED’ charge transport mechanism. The morphological analysis of the Cu 2– x Se electrode, carried out using atomic force microscopy, as well as the temperature dependence of the current–voltage measurements in the OLED (50–300 K) shows the ideal deposition time in the chemical bath. In contrast, impedance spectroscopy results confirm the inexistence of the Cu 2– x Se/PEDOT:PSS interface using 30 s to Cu 2– x Se synthesis. As a result, the control of the injection mechanism of charges can be obtained by reducing the barrier energy to hole transport during the synthesis process of the Cu 2– x Se layer via chemical bath deposition, thus simplifying and reducing the costs of the device's processing.