Up-converted photoluminescence from $\mathrm{C}{\mathrm{H}}_3\mathrm{N}{\mathrm{H}}_3\mathrm{Pb}{\mathrm{I}}_3$ perovskite semiconductors: Implications for laser cooling

Up-converted photoluminescence (PL), or, in other words, anti-Stokes PL via phonon absorption in semiconductors is a critical property for realizing optical refrigeration. Here, we investigate the anti-Stokes PL from optically thin films and thick crystals of $\mathrm{C}{\mathrm{H}}_3\mathrm{N}{\mathrm{H}}_3\mathrm{Pb}{\mathrm{I}}_3$ to assess their potential for laser cooling. Using PL excitation spectroscopy, we determine the excitation photon energy that maximizes the cooling efficiency. The evaluated up-conversion gain for the thick single crystal is close to 70% of that for the thin film, indicating a possibility for laser cooling even in thick crystals. We discuss the competition between anti-Stokes PL and photon reabsorption in $\mathrm{C}{\mathrm{H}}_3\mathrm{N}{\mathrm{H}}_3\mathrm{Pb}{\mathrm{I}}_3$.

Figure 1

(a) Two-dimensional PLE map of the $\mathrm{MAPb}{\mathrm{I}}_3$ thin film. (b) Two-dimensional PLE map of the $\mathrm{MAPb}{\mathrm{I}}_3$ thick single crystal. (c) Five representative PL spectra of the $\mathrm{MAPb}{\mathrm{I}}_3$ thin film. The corresponding excitation energies employed here were 1.72, 1.64, 1.60, 1.58, and 1.57 eV. (d) Five representative PL spectra of the $\mathrm{MAPb}{\mathrm{I}}_3$ thick single crystal. The corresponding excitation energies employed here were 1.65, 1.57, 1.53, 1.51, and 1.50 eV. (e) Excitation-energy dependences of the PL peak energies. The red and blue dot lines show the dependences for the thin film and thick single crystal, respectively. The black line corresponds to the excitation energy. The right side of this line corresponds to S-PL dominant region, and the left side corresponds to AS-PL dominant region.

Figure 2

(a) S-PLE (red) and AS-PLE (blue) spectra for the $\mathrm{MAPb}{\mathrm{I}}_3$ thin film, and S-PLE (green) and AS-PLE (pink) spectra for the $\mathrm{MAPb}{\mathrm{I}}_3$ thick single crystal. (b) The up-conversion gain spectrum ($\mathrm{\Delta }{I}_{\mathrm{PLE}}$) of the $\mathrm{MAPb}{\mathrm{I}}_3$ thin film and thick single crystal plotted as a function of $E_{\mathrm{ex}}-E_{\mathrm{eq}}$ for easy comparison. The zero cross point of $\mathrm{\Delta }{I}_{\mathrm{PLE}}$ corresponds to $E_{\mathrm{ex}}=E_{\mathrm{eq}}$. The red and blue data stand for the thin film and thick single crystal, respectively. The solid lines are the fitting results using Eq. (5).

Figure 3

Plot of the excitation-energy dependence of the ratio between the intensities of the AS-PL and the total PL spectrum. The red and blue dot lines are the dependence for the thin film and thick single crystal, respectively.

Figure 4

(a) Spontaneous emission (red) and absorption (blue) spectra used for the calculation. These spectra are calculated from the ellipsometry data in Ref. [35]. (b) Theoretical sample-thickness dependence of the optimized excitation energy ($E_{\mathrm{opt}}$, upper panel) and the maximum value of the up-conversion gain ($\mathrm{\Delta }{I}_{\max }$, lower panel). $L_D$ corresponds to the diffusion length of the sample including photon recycling effects.

Figure 5

(a) PL spectrum of the $\mathrm{MAPb}{\mathrm{I}}_3$ single crystal for an excitation energy of 1.8 eV. The red data shows to the experimental result and the blue line is the fitting result. (b) Calculated two-dimensional PLE map of the thick single crystal. The diagonal orange line is an eye guide indicating the excitation energy.