What is the suitable excitation wavelength for Time Resolved Photoluminescence (TRPL) measurement for perovskite (CH3NH3PbI3)? How to find the emission wavelength at which data should be collected? I have measured TRPL of perovoskite film (coated on glass) at excitation wavelength of 379 nm for emission wavelength of 380, 400........840 nm using Time-Resolved Spectroscopy System (Reg A/Chameleon/PicoQuant) but a small peak is observed at 380 nm only. Which gives carrier lifetime ~ 2 ns. What is the actual problem? and how to solve it?
You can excite MAPbI3 at any wavelength that it absorbs light. However when you excite the material at a much higher energy than the bandgap, you will generate hot carriers. the Typical bandgap of MAPbI3 is ~750 nm or 1.6 eV. By taking an absorption spectrum of the film, you can see what wavelengths of light it absorbs (which it should absorb the whole visible range, and have a peak/drop off around 750 nm). That 380 nm peak you are observing in TRPL is most likely residual laser. Try using a better long pass filter (or if it’s a commercial set up, Use a different wavelength — like 700 nm). The emission around 840 nm is what you want to be measuring the lifetime of, however the peak seems redshifted — perovskites should have a much much longer PL lifetime than the 2 ns. i have measured films ranging in PL lifetime from 80 ns to 0.5 us.
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