Efficient polymer solar cells fabricated on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)-etched old indium tin oxide substrates.

In organic electronic devices, indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are the most common transparent electrode and anodic buffer layer materials, respectively. A widespread concern is that PEDOT:PSS is acidic and etches ITO. We show that this issue is not serious: only a few nanometers of ITO are etched in typical device processing conditions and storage thereafter; conductivity losses are affordable; and optical transmission gains further offset these losses. Organic photovoltaic (OPV) devices fabricated on old ITO (with PEDOT:PSS history) were similar or higher in efficiency than devices on fresh ITO. Poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7) devices on old ITO showed efficiencies up to 9.24% compared to 8.72% efficient devices on fresh ITO. This reusability of ITO can be impactful for economics of organic electronics because ITO accounts for almost 90% of energy embedded in devices, such as OPVs.