1, The University of Texas at Dallas, Richardson, Texas, United States
Halide-based perovskite compounds have rapidly evolved as versatile and promising materials for low-cost, high performance optoelectronics applications, including solar cells, lasers, light emitting diodes (LEDs) and photodetectors. Among these, all inorganic CsPbX3 (X=Br, I or Cl) perovskites attract particular attention due to enhanced environmental stability and wavelength tunability. Their photoluminescence (PL) properties can be further tuned by the choice of the desired halide precursor or anion exchange reactions. Until now, no regard for iterative self-absorption and photon re-emission that affect light propagation within the strongly absorbing CsPbBr3 perovskite media has been made. In this work, we provide detailed spectroscopic evidence of PL trapping and sequential photon absorption/re-emission in CsPbBr3 perovskite microwires. Using two-photon excitation, time-resolved PL lifetimes and emission spectra are measured as function of lateral distance between PL excitation and collection positions along the microwire, with separations up to several hundred microns. Significant PL lifetime lengthening, appearance of the well-resolved PL risetimes and low-energy emission spectral shift provide evidence of sequential processes of self-absorption/re-emission that efficiently recycle photons within the microwire waveguide. The quantitative modeling accounting for bi-molecular electron/hole recombination and radiation trapping within the microwire agrees well with the measured decay modifications. The model affirms high intrinsic quantum yield values of CsPbBr3 perovskite microwires that are necessary for the observable effects of photon recycling. Such findings provide crucial information about potential impact of photon recycling/waveguide trapping on optoelectronic properties of CsPbBr3 materials.