Light induced metastable modification of optical properties in CH3NH3PbI3?xBrx perovskite films: Two-step mechanism |
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| Affiliation: | 1. School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China;2. Institute of Functional Nano & Soft Materials (FUNSOM) & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123, China;1. State Key Laboratory of Luminescent Materials and Devices, Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510640, China;2. Key Lab of Environment-Friendly Chemistry and Application in Ministry of Education, College of Chemistry, Xiangtan University, Xiangtan 411105, China;3. School of Materials Science and Engineering, Changzhou University, Changzhou 213164, China;1. Photovoltaic Technology Team, Samsung SDI, CheonanSi 331-300, South Korea;2. Department of Polymer Science and Engineering, Pusan National University, Busan 609-735, South Korea;1. College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, China;2. School of Chemical Engineering, Northwest University, Xi’an 710069, China;3. National Institute of Clean-and-Low-Carbon Energy, Beijing 102209, China;4. SINOPEC Shanghai Research Institute of Petrochemical Technology, Shanghai 201208, China;1. Research Laboratory of Electronics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA;2. Department of Chemical Engineering, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, the Netherlands;3. Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK;4. Department of Chemistry, University of Bath, Bath BA2 7AY, UK;5. Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK;1. Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo, OH 43606, United States;2. Chemical and Materials Science Center, National Renewable Energy Laboratory, Golden, CO 80401, United States;3. Institute of Advanced Materials and Key Laboratory for Organic Electronics & Information Displays, Nanjing University of Posts & Telecommunications, Nanjing 210023, PR China |
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| Abstract: | We have used photoluminescence (PL) and photomodulation (PM) spectroscopy to investigate the reversible spectral changes of PL in CH3NH3PbI3?xBrx films, where x is 1.7. In an as-prepared film, the peak of PL spectra shifts from ～640 nm near bandedge to ～750 nm after excitation by a continuous wave (CW) or a pulsed laser with high repetition rate, but keeps at 640 nm excited by same pulsed laser with the repetition rate smaller than 500 Hz. The PM spectroscopy also shows the formation of sub bandgap states after illumination which is responsible for the red shift of PL. The light induced modification of optical properties is reversible after keeping the film out of illumination for several hours at room temperature. We analyze the photoinduced modification to be two-steps processes: the temporary sub bandgap states were first photogenerated in perovskite film, if those states interacting with more coming photons within their lifetimes, light induced metastable states responsible for red-shift of PL will be formed. This instability reduces the electronic bandgap and generates more traps which will degrade the performance of the related photovoltaic devices. |
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| Keywords: | Mixed iodide-bromide perovskite Light induced spectral change Metastable state |
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