Platinum (II)-bis (aryleneethynylene) complexes for solution-processible molecular bulk heterojunction solar cells

Four new solution-processible small-molecular platinum(II)-bis( aryleneethynylene) complexes consisting of benzothiadiazole as the electron acceptor and triphenylamine and/ or thiophene as the electron donor were conveniently synthesized and characterized by physicochemical and computational methods, and utilized as the electron-donor materials in the fabrication of solution-processed bulk heterojunction (BHJ) solar cells. The effect of different electron-donor groups in these small molecules on the optoelectronic and photovoltaic properties was also examined. The optical and time-dependent density functional theory studies showed that the incorporation of stronger electron-donor groups significantly enhanced the solarabsorption abilities of the complexes. These molecular complexes can serve as good electron donors for fabricating BHJ devices by blending them with the [6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) as the electron acceptor. The best power conversion efficiency of 2.37% was achieved with the open-circuit voltage of 0.83 V, short-circuit current density of 7.10 mAcm-2and fill factor of 0.40 under illumination of an AM 1.5 solar-cell simulator. The spin-coated thin films showed pchannel field-effect charge transport with hole mobilities of up to 2.4× 10-4cm2V-1s-1for these molecules. The present work illuminates the potential of well-defined organometallic complexes in developing light-harvesting small molecules for efficient power generation in organic photovoltaics implementation. KGaA, Weinheim.