Dicyanovinyl substituted oligothiophenes: Thermal stability, mobility measurements, and performance in photovoltaic devices

A series of dicyanovinyl-oligothiophenes are investigated concerning their thermal stability, absorption in thin film, and hole mobility. Due to very high extinction coefficients, these materials are interesting for application as donor in solar cells. The quinquethiophene DCV 2-5T, which shows a hole mobility of 2.2×10 –5 cm 2/Vs, is used as donor material in a flat heterojunction organic small molecule solar cells. Despite a very thin donor layer of only 6 nm, these devices exhibit in a planar heterojunction with 15 nm C 60 an efficiency of up to 2.8% with a fill factor of up to 58%, a short circuit current density of 5.2 mA/cm 2, an open circuit voltage of 1.03 V, and an external quantum efficiency of 30% in the green spectral range. [Display omitted] ► 2,2-Dicyanovinyl substituted oligothiophenes are investigated by different methods. ► TG measurements show a high thermal stability (up to 370 °C). ► Absorption measurements reveal bathochromic tendency with growing π-system. ► OFET-measurements exhibit high hole mobility dependent on length of π-system. ► Flat heterojunction solar cells show good performance despite very thin donor layer.