GRÄTZEL Michael Swiss Federal Institute of Technology in Lausanne

Solar cells using dyes or semiconducting pigment particles as light harvesters supported by mesoscopic oxide films have emerged as credible contenders to conventional p-n junction photovoltaics [1]. Separating light absorption from charge carrier transport, dye sensitized mesoscopic solar cells (DSSCs) were the first to use a three-dimensional nanocrystalline junction for solar electricity production. Molecularly engineered donor-acceptor porphyrine dyes reach currently a power conversion efficiency (PCE) of up to 13 percent [2,3] under standard air mass 1.5 (AM1.5) reporting conditions (25°C, 1000 Watt/m2 solar intensity) Recently another breakthrough was witnesses with the meteoric rise of metal halide perovskites as powerful light harvesters for thin film photovoltaics [4]. Solid state mesoscpic cells based on CH3NH3PbI3 pigments supported by a nancorystalline TiO2 scaffold and organic or inorganic hole conductors have now reached a certified power conversion efficiency of 17.9 % and further rapid improvements in performance appear to be feasible. Carrier diffusion lengths extending over 100 mm have been measured [5] even from solution processed perovskite solar cells (PVCs) and very stableef embodiments based on carbon current collectors have recently been realized. LITERATURE: 1. M. Grätzel Nature 414, 338 (2001). 2. A.Yella, H.-W. Lee, H. N. Tsao,1 C. Yi, A.Kumar Chandiran, Md.K. Nazeeruddin, EW-G Diau,,C.-Y Yeh,2 S. M. Zakeeruddin and M. Grätzel Science 629, 334 (2011). 3. S. Mathew, A. Yella, P, Gao, R. Humphry-Baker, B.F.E. Curchod, N. Ashari-Astani I.Tavernelli, U. Rothlisberger, Md.K. Nazeeruddin, M. Grätzel. Nature Chemistry S. Mathew, A. Yella, P, Gao, R. Humphry-Baker, B.F.E. Curchod, N. Ashari-Astani,I.Tavernelli, U. Rothlisberger, Md.K. Nazeeruddin, M. Grätzel Nature Chemistry, 6, 242-247 (2014) 4. J. Burschka, N. Pellet, S.-J. Moon, R.Humphry-Baker, P. Gao1, M K. Nazeeruddin1 and M. Grätzel, Nature 499, 316-319 (2013)J. 5. G.C Xing, N.,Mathews, S.Y. Sun, S.S. Lim, Y.M., Lam, M Grätzel., N., S. Mhaisalkar and T.C.. Sun Science 342, 344_347 (2013). S.,