Thin Film Photovoltaics with Organic Metal Halide Peroviskites

Organic metal halide perovskites have now emerged as new and promising candidates for developing low cost thin film solar cells with efficiencies in the range of 20.1% certified efficiency.  The recent advances of CH₃NH₃PbI₃ based thin film solar cells have manly focused on the design architecture and improving the stability. Both TiO2 and Al2O3 mesoscopic architectures provide robust support to design high efficiency thin film solar cells. The excited state dynamics leading to the charge separation remains to be fully understood. Through comparative spectral analysis between the absorption features of charge transfer complexes in the solution phase and the final solid-state perovskite films, we are able to fully classify the absorption features in the excited state of CH₃NH₃PbI₃ across the transient absorption spectrum recorded following laser pulse excitation. The excited state of CH₃NH₃PbI₃ characterized through transient absorption spectroscopy show dual behavior, viz., charge transfer complex state and charge separated state.^1,2 The interplay between these two different excited states leads to efficient charge separation. Insights into the charge recombination kinetics and band filling aspects of CH₃NH₃PbI₃ provide new ways to tune the efficiency of perovskite solar cells. These spectroscopic studies provide further insight into the optoelectronic behavior of methyl ammonium lead iodide films.  Excited state properties that elucidate the exceptional photovoltaic properties will be discussed.

Acknowledgments

The research described herein is supported by the Office of Basic Energy Sciences, U.S. Department of Energy.

 

Selected Publications

1. Christians, J. A.; Fung, R.; Kamat, P. V., An Inorganic Hole Conductor for Organo-Lead Halide Perovskite Solar Cells. Improved Hole Conductivity with Copper Iodide. J. Am. Chem. Soc. 2014, 136, 758–764.
2. Manser, J. S.; Kamat, P. V., Band Filling with Charge Carriers in Organometal Halide Perovskites. Nature Photonics 2014, DOI: 10.1038/NPHOTON.2014.1171.