Molecular Photovoltaics and Perovskite Solar Cells
Michael Graetzel

Ecole Polytechnique Fédérale de Lausanne (EPFL),

Lausanne, Switzerland

michael.graetzel@epfl.ch

 

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. Remarkably the PCE increase to 29% in ambient light exceeding 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) [4-6]. 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 over 22 %, exceeding the PCE of polycrystalline silicon solar cells. These photovoltaics show intense electro-luminesence. and Voc values over 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 [7,8].

 

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) pp 7377-7381.

 

2. M. Grätzel, “Photoelectrochemical Cells,” Nature 414 (2001). pp 332-344.

 

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,“ Science 629 (2011) pp 334-341.

 

4. M. Grätzel, Light and Shade of Perovskite Solar Cells, Nature Mat. 13 (2014) pp 838-842.

 

5. J. Burschka, N. Pellet, S.-J. Moon, R.Humphry-Baker, P. Gao1, M K. Nazeeruddin and M. Grätzel, „Sequential deposition as a route to high-performance perovskite-sensitized solar cells“ Nature 499, (2013),pp 316-3199.

 

6. 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), pp 58-62.

 

7. 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 Science, 345, (2014), pp 1593-1596.

 

8. M.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) , pp 7326-7332.