Application of a water-soluble metallophthalocyanine derivative as a cathode interlayer for the polymer solar cells

Abstract

A water-soluble metallophthalocyanine (MPc) derivative, 2,3,9,10,16,17,23,24-octakis(2-trimethylaminoethylsulfanyl) zincylphthalocyanine octaiodine (ZnPc[S(CH2)2N-(CH3)3I]8) was synthesized and applied in polymer solar cells (PSCs). A power conversion efficiency (PCE) of 7.06% has been obtained when the ZnPc[S(CH2)2N(CH3)3I]8 was utilized as a cathode interlayer in the PSCs based on a blend of PCDTBT (poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]) and PC71BM ([6,6]-phenyl C71 butyric acid methyl ester) as an active layer. Ultraviolet photoemission spectroscopic (UPS), atomic force microscopy (AFM), contact angle (θ) and mobility measurements demonstrated that an introduction of ZnPc[S(CH2)2N(CH3)3I]8 between active layer and cathode decreased work function of cathode, increased hole mobility and facilitated a balance of electron and hole transport in the PSCs, resulting in a simultaneous improvement of open-circuit voltage, short-circuit current and fill factor.