Journal
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
Volume 8, Issue 19, Pages 4912-4917Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpclett.7b02286
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Funding
- Basic Science Research Program through the National Research Foundation of Korea (NRF) - Korean government [2017R1D1A1B0303539, 2015R1D1A3A03019609]
- Priority Research Centers Program through the National Research Foundation of Korea (NRF) - Korean government [2009-0093818]
- Basic Research Lab Program through the National Research Foundation of Korea (NRF) - Korean government [2014R1A4A1071686]
- U.S. Department of Energy, Office of Science [SC0012541]
- National Research Foundation of Korea [2015R1D1A3A03019609] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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CsPbBr3 is a direct-gap semiconductor where optical absorption takes place across the fundamental bandgap, but this all-inorganic halide perovskite typically exhibits above-bandgap emission when excited over an energy level, lying above the conduction-band minimum. We probe this bandgap anomaly using wavelength-dependent multiphoton absorption spectroscopy and find that the fundamental gap is strictly two-photon forbidden, rendering it three-photon absorption (3PA) active. Instead, two-photon absorption (2PA) commences when the two-photon energy is resonant with the optical gap, associated with the level causing the anomaly. We determine absolute nonlinear optical dispersion over this 3PA-2PA region, which can be explained by two-band models in terms of the optical gap. The polarization dependence of 3PA and 2PA is also measured and explained by the relevant selection rules. CsPbBr3 is highly luminescent under multiphoton absorption at room temperature with marked polarization and wavelength dependence at the 3PA-2PA crossover and therefore has potential for nonlinear optical applications.
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