Highly Efficient Solar Cells Using Organic Dyes with Amorphous Moiety

Novel organic sensitizers comprising donor; electron-conducting, and anchoring groups were engineered at molecular level and synthesized. The functionalized unsymmetrical organic sensitizers 3-{5-[N,N-Bis(9,9-dimethylfluorene-2-yl)phenyl]-thiophene-2-yl}-2-cyano-acrylic acid (JK-1) and 3-{5'-[N,N-Bis(9,9-dimethylfluorene-2-yl)phenyl]-2,2'-bithiophene-5-yl}-2-cyano-acrylic acid (JK-2), upon anchoring onto TiO2 film exhibit unprecedented incident photon to current conversion efficiency 91 %. The photovoltaic data using an electrolyte having composition of 0.6M M-methyl-N-butyl imidiazolium iodide, 0.04 M iodine, 0.025 M LiI, 0.05M guanidinium thiocyanate and 0.28 M tert.butylpyridine in 15/85 (v/v) mixture of valeronitrile and acetonitrile revealed a short circuit photocurrent density of 14.0 mA/cm2, an open circuit voltage of 753 mV and a fill factor of 0.76, corresponding to an overall conversion efficiency of 8.01 % under standard AM 1.