Four-Wave Mixing in Perovskite Photovoltaic Materials Reveals Long Dephasing Times and Weaker Many-Body Interactions than GaAs

• Published in: ACS photonics Vol. 4; no. 6; pp. 1515 - 1521
• Main Authors: March, Samuel A, Riley, Drew B, Clegg, Charlotte, Webber, Daniel, Liu, Xinyu, Dobrowolska, Margaret, Furdyna, Jacek K, Hill, Ian G, Hall, Kimberley C
• Format: Journal Article
• Language: English
• Published: American Chemical Society 21.06.2017
• Subjects: carrier−carrier scattering; perovskite; four-wave mixing; many-body effects; solar cell; photovoltaic
• ISSN: 2330-4022; 2330-4022
• DOI: 10.1021/acsphotonics.7b00282

Perovksite semiconductors have shown promise for low-cost solar cells, lasers and photodetectors, yet their fundamental photophysical properties are not well understood. Recent observations of a low exciton binding energy and evidence of hot phonon effects in the room temperature phase suggest that perovskites are much closer to inorganic semiconductors than the absorber layers in traditional organic photovoltaics, signaling the need for experiments that shed light on the placement of perovskite materials within the spectrum of semiconductors used in optoelectronics and photovoltaics. Here we use four-wave mixing (FWM) to contrast the coherent optical response of CH3NH3PbI3 thin films and crystalline GaAs. At carrier densities relevant for solar cell operation, our results show that carriers interact surprisingly weakly via the Coulomb interaction in perovskite, much weaker than in inorganic semiconductors. These weak many-body effects lead to a dephasing time in CH3NH3PbI3 ∼ 3× longer than in GaAs. Our results also show that the strong enhancement of the exciton FWM signal tied to excitation-induced dephasing in GaAs and other III–V semiconductors does not occur in perovskite due to weak exciton–carrier interactions.