XPS Analysis of the Improved Operational Stability of Organic Solar Cells Using a V2O5 and PEDOT:PSS Composite Layer: Effect of Varied Atmospheric Conditions

This work investigates the enhanced stability of organic solar cells (OSCs) fabricated with a hybrid hole-transport layer (HTL) incorporating vanadium pentaoxide (V2O5) nanoparticles in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). OSCs have, been fabricated in controlled and ambient atmospheric conditions by employing a pristine PEDOT:PSS HTL and its hybrid variant. Stability and degradation analyses were carried out by using photovoltaic and X-ray photoelectron spectroscopy (XPS) measurements, respectively. Normalized photovoltaic characteristics showed that OSCs with hybrid HTL outperformed the pristine device and retained their performance as compared to their pristine counterparts when the fabrication was carried out in a nitrogen filled glovebox and devices were tested after encapsulation for 7 days. However, OSCs that were fabricated and characterized in ambient air showed severe degradation in photovoltaic performance, mainly due to a drastic decay in the short circuit current and open circuit voltage for both device variants. Further, XPS was applied to probe the stability of HTL variants under aging in ambient air. The device instability was mainly ascribed to indium diffusion from the anode into the HTL and its concentration increased from 0.4 to 2.8% within 250 h of ambient exposure of pristine HTL, while an insignificant increase was recorded in the indium content of the hybrid HTL. This confirms the remarkable reduction in indium diffusion brought about by the presence of V2O5 nanoparticles.