Enhancing the durability of polymer solar cells using gold nano-dots

The durability of organic photovoltaic devices is improved by (a) replacing thermally labile poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) with gold nano-dots and (b) stabilizing the morphology of photoactive layers through thermally induced reaction. Gold nano-dots (Au-ND) (3–6 nm in diameter and 0.8 nm in height) were thermally deposited on ITO substrates prior to depositing a hole transporting layer (40 nm) of an azide-functionalized poly(3-hexylthiophene), P1, which was insolubilized by heating to 150 °C. A blend of P1 and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) was deposited and heated to 150 °C prior to the deposition of a Ca/Al cathode. The reaction of P1 with PCBM stabilized the bulk heterojunction film as evidenced by the suppression of crystallization of PCBM. Replacement of PEDOT:PSS with Au-ND, in combination with morphological stabilization, greatly improves the durability of PV devices under accelerated lifetime testing at 150 °C. Power conversion efficiencies (PCE) for the P1:PCBM devices stabilized at 1.25% after 28 h of accelerated testing at 150 °C, whereas conventional P3HT:PCBM devices on PEDOT/ITO dropped to 0.58% after only 7 h of accelerated testing. Prospects for similarly enhancing the durability of highly efficient PV devices are discussed.