LAUSR

Abstract We report the synthesis of three new push-pull dyes specially designed for the sensitization of mesoporous p type semi-conductor NiO for the construction of p type dye sensitized solar cells (pDSC). Their structure stems from the conjugation of the well-known tris(carboxy-arlyamine) anchoring moiety to a benzothiadiazole acceptor through a fluorene ( PP1 ) or thiophene-fluorene linker ( PP2 ). Appending a NDI secondary acceptor onto PP2 yielded a dyad ( PP2-NDI ). The push-pull structure is here particularly adapted to the sensitization of p-type semi-conducting materials. All three dyes were investigated by spectroscopic and electrochemical techniques, and their electronic properties were modelled by TD-DFT. In all cases, the new sensitizers exhibit adequate absorption features (spanning from 400 nm to 600 nm, extinction coefficients between 20000 and 27000 M −1  cm −1 ) and their thermodynamic parameters are all in favor of efficient interfacial charge transfers involving NiO. pDSC were constructed with all three dyes; high photoconversion efficiencies (PCE) were reached, especially in the case of dyad PP2-NDI (Jsc = 5.90 mA/cm 2 , Voc = 143 mV, FF = 33.8%, PCE = 0.29%), due to a combination of outstanding electronic properties and increased charge separation state lifetime. Tandem DSC (tDSC) composed of a TiO 2 photoanode sensitized by the dye D35 and a NiO photocathode sensitized by PP2-NDI were assembled with two different electrolytes (I 3 − /I − or T 2 /T − based electrolytes). The latter gave PCE among the best ever reported for tDSC (Jsc = 5.90 mA/cm 2 ; Voc = 896 mV; FF = 63%, PCE = 2.80% in the case of the I 3 − /I − electrolyte, Jsc = 4.52 mA/cm 2 , Voc = 840 mV, FF = 60% and PCE = 2.27% for T 2 /T − based devices) unraveling the significance of the new dyes presented in this study.