Plenary Session, Award Lecture
Molecular Photovoltaics and Mesoscopic Solar Cells (Paracelsus Award Lecture 2016)
M. Grätzel1
1EPF Lausanne
Mesoscopic photovoltaics have emerged as credible contenders to conventional p-n junction photovoltaics [1-3]. Mimicking light harvesting and charge carrier generation in natural photosynthesis, dye sensitized solar cells (DSCs) were the first to use three-dimensional nanocrystalline junctions for solar electricity production, reaching currently a power conversion efficiency (PCE) of over 14% in standard air mass 1.5 sunlight. Remarquably the PCE increase to 26% in ambient light matching the performance of GaAs photovoltaics. By now, large-scale DSC production and commercial sales have been launched on the multi-megawatt scale for application in building integrated PV and light weight flexible power sources. Recently, the DSC has engendered the meteoric rise of perovskite solar cells (PSCs) [4,5]. Today’s state of the art devices employ metal halide perovskite of the general composition ABX3 as light harvesters, where A stands for methylammonium, formamidinium or caesium, B denotes lead or tin and X iodide or bromide. Carrier diffusion lengths in the 100 nm - micron range have been measured for solution-processed perovskites and certified power conversion efficiencies (PCEs) attain 22%, exceeding the PCE of polycrystalline silicon solar cells. These photovoltaics show intense electro-luminesence matching the external quantum efficiency of silicon solar cells. and Voc values close to 1.2 V for a 1.55 eV band gap material. This renders perovskite-based photosystem very attractive for applications in tandem cells and for the generation of fuels from sunlight mimicking natural photosynthesis [6,7].
[1] B. O’Regan and M. Grätzel, “A Low Cost, High Efficiency Solar Cell based on the Sensitization of Colloidal Titanium Dioxide”,Nature 353 (1991), pp7377-7381.
[2] M. Grätzel, “Photoelectrochemical Cells”,Nature 414 (2001), pp332-344.
[3] A.Yella, H.-W. Lee, H. N. Tsao, C. Yi, A. Kumar Chandiran, Md.K. Nazeeruddin, EW-G. Diau, C.-Y Yeh, S. M. Zakeeruddin and M. Grätzel, “Porphyrin-based Solar Cell with Co(II/III) Redox Electrolyte Exceed 12% Efficiency“, Science629 (2011), pp334-341.
[4] M. Grätzel, "Light and Shade of Perovskite Solar Cells", Nature Mat. 13 (2014), pp838-842.
[5] J. Burschka, N. Pellet, S.-J. Moon, R. Humphry-Baker, P. Gao, M K. Nazeeruddin and M. Grätzel, "Sequential deposition as a route to high-performance perovskite-sensitized solar cells“ Nature499, (2013), pp316-3199.
[6] J. Luo, J.-H. Im, M.T. Mayer, M. Schreier, Md.K. Nazeeruddin, N.-G. Park, S.D.Tilley, H.J. Fan, M. Grätzel, "Water photolysis at 12.3% efficiency via perovskite photovoltaics and Earth abundant catalysts", Science345 (2014), pp1593-1596.
[7] X. Li, D. Bi, C. Yi, J.-D. Décoppet, J. Luo, S.M. Zakeeruddin, A. Hagfeldt, M. Grätzel, "A vacuum flash–assisted solution process for high-efficiency large-area perovskite solar cells", Science 353 (2016), pp58-62.
[8] Schreier L. Curvat, F. Giordano, L. Steier, A. Abate, S.M. Zakeeruddin, J. Luo, M. Mayer and M. Grätzel,"Efficient photosynthesis of carbon monoxide from CO2 using perovskite photovoltaics",Nature Commun. 6 (2015), pp7326-7332.