Altering the Optoelectronic Properties of the PEDOT:PSS Hole Transport Layer with Sodium Polystyrenesulfonate to Enhance the Efficiency and Stability of Perovskite Light-Emitting Diode

Altering the optoelectronic properties of the widely used hole transport layer (HTL), namely, poly-(3,4-ethylenedioxythiophene)-poly-(styrenesulfonate), commonly known as PEDOT:PSS, with sodium polystyrenesulfonate (Na-PSS) overcomes limitations of the conventional pristine PEDOT:PSS HTL-based optoelectronic devices. The introduction of Na-PSS into pristine PEDOT:PSS results in a reduced energy barrier between the HTL and light-emission layer (EML), leading to improved hole injection, thereby lowering the turn-on voltage and improving the perovskite light-emitting diode (Pe-LED) efficiency. The pH value of acidic pristine PEDOT:PSS is modulated by the addition of Na-PSS, which aids in preventing the corrosion of the underlying semitransparent indium-doped tin oxide (ITO) electrode. The modulation of the pH value resulted in higher thermal tolerance of the perovskite emission layer coated on top of the HTL. The introduction of Na-PSS creates a PSS-rich environment, which prevents nonradiative recombination of excitons at the HTL/EML interface. This enhances the efficiency of the Pe-LED device by allowing more excitons to recombine radiatively. Moreover, the addition of Na-PSS modulates the conductivity of pristine PEDOT:PSS, resulting in effective confinement of charge carriers within the EML, increasing the probability of electron-hole recombination within the EML, and improving the device efficiency. The use of Na-PSS-modified PEDOT:PSS significantly enhances the performance of the Pe-LED device, and the efficiency values outperformed those of pristine PEDOT:PSS-based Pe-LED devices. The Pe-LED devices with Na-PSS-modified HTL have a low turn-on voltage (2.8 V)@1 cd/m², high external quantum efficiency (EQE) of 10.05%, and current and power efficiency of 40.89 cd/A and 35.95 lm/W, respectively. Most notable advantage of the Na-PSS-modified HTL is the significant improvement in the operational stability of the Pe-LED devices, with the electroluminescent (EL) lifetime 4 times longer in comparison to that of Pe-LED devices having pristine PEDOT:PSS as HTL.