Origin of Long Lifetime of Band-Edge Charge Carriers in Lead Iodide Solar Cell Perovskites
Tianran Chen1, Wei-Liang Chen2*, Benjamin J. Foley3, Jooseop Lee4, Jacob P. C. Ruff4, J. Y. Peter Ko4, Craig M. Brown5, Leland W. Harriger5, Depei Zhang1, Changwon Park6, Mina Yoon6, Yu-Ming Chang2, Joshua J. Choi3, Seung-Hun Lee1
1Department of Physics, University of Virginia, Charlottesville, VA 22904, USA
2Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
3Department of Chemical Engineering, University of Virginia, Charlottesville, USA
4Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY 14853, USA
5NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
6Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
* Presenter:Wei-Liang Chen, email:wechen@ntu.edu.tw
Hybrid organic-inorganic perovskites (HOIPs) are among the most promising materials for next generation solar cells that combine high efficiency and low-cost. Its high performance as a photovoltaic material is closely related to its long carrier lifetime. Using photoluminescence, time resolved photoluminescence, and neutron scattering measurements, we show[1] that the screening of band-edge charge carriers by the rotation of organic cation molecules provides a major contribution to the long carrier lifetime. Our results reveal that the band-edge carrier lifetime increases when HOIPs changes from a lower rotational entropy phase to a higher entropy phase. These results imply that the recombination of the photo-excited electrons and holes is suppressed by screening, leading to polaron formation that extend the lifetime. This insight can guide the search for HOIPs with the best solar cell performance.

[1] Origin of Long Lifetime of Band-Edge Charge Carriers in Organic-Inorganic Lead Iodide Perovskites, Tianran Chen et al., Proceedings of National Academy of Sciences 114, 7519-7524, (2017).

Keywords: organic-inorganic hybrid perovskite, carrier lifetime, photoluminescence, polaron