Temperature-dependent photoluminescence spectra and decay dynamics of MAPbBr3 and MAPbI3 thin films

Abstract

The steady-state spectra and fluorescence lifetimes are investigated under vacuum for methylammonium lead bromide and iodide (CH3NH3PbBr3 or MAPbBr3, and CH3NH3PbI3 or MAPbI3) thin films by stably controlling the sample temperature in the range of 78 K to 320 K. The transformation of spectrum features and lifetime components are proved to be quite sensitive to the temperatures in accordance with the phase transition of structures. Our work demonstrates that the halide anions I- and Br- lead to remarkable differences on optical characteristics. Due to the distinct behaviors of excitons, electron-hole pairs and free carriers in decay channels, MAPbI3 has much longer lifetime and higher low-temperature fluorescence efficiency than those of MAPbBr3. The findings provide possible choices for certain perovskites under various ambient temperature conditions to display photovoltaic or luminescent advantage.

Spontaneous Formation of Nanocrystals in Amorphous Matrix: Alternative Pathway to Bright Emission in Quasi‐2D Perovskites

“…The reduction of this emission is consistent with the reduction of defect concentration in P4L samples, as well as previous report that amorphous regions at grain boundaries result in increased PL intensity and lifetime . In addition to defects, other possible reasons for the appearance of low energy peak at low temperatures include phase transitions, self‐trapped excitons, and bound excitons . The phase change with temperature in the range of 70–320 K in MAPbBr 3 leads to a peak shift in the range of 2.27–2.37 eV, which is similar to the peak shifts observed here, as shown in Figure d.…”

“…In addition to defects, other possible reasons for the appearance of low energy peak at low temperatures include phase transitions, self‐trapped excitons, and bound excitons . The phase change with temperature in the range of 70–320 K in MAPbBr 3 leads to a peak shift in the range of 2.27–2.37 eV, which is similar to the peak shifts observed here, as shown in Figure d. However, the peak at ≈580 or ≈2.14 eV is outside of this range and thus unlikely to originate from any phase impurity since quasi‐2D material emissions will be blue shifted compared to 3D MAPbBr 3 .…”

Bright and fast scintillation of organolead perovskite MAPbBr3 at low temperatures

“…An analysis of the plots reveals further details in the temperature evolution of the luminescence kinetics of the crystal. As can be derived from the decay time versus temperature dependence, the fast and slow decay time constants in the crystal are about 0.1 and 1 ns at T 4 50 K. This correlates well with the results from photoluminescence decay studies of MAPbBr 3 down to 77 K. 32 With cooling to lower temperatures, the decay rate of the luminescence kinetics in MAPbBr 3 exhibits steep changes, resulting in a significant increase of the decay time constants, so that at T = 8 K, t f = 2 ns and t s = 50 ns. The amplitudes of the fast and slow components initially increase with cooling, while below 40 K they start to decrease; in particular, the amplitude of the fast component decreases by about a factor of five.…”

“…5 Numerous studies on the luminescence properties of MAPbX 3 , X = Br and I, were conducted over a wide temperature range, evidencing that free charge carriers dominate at room temperature, while excitons are stable at low temperature. [32][33][34][35] Upon high-energy excitation, the thermalized electrons and holes form free excitons, which in turn can interact with defects or impurities. The narrow luminescence bands with a small Stokes shift observed in OTPs at low temperature are attributed to free and bound excitons.…”

Methylammonium Lead Tribromide Single Crystal Detectors towards Robust Gamma‐Ray Photon Sensing

“…The phase transition for MAPbBr 3 crystal occurs near 160 K which is also not the origin for a sharp decrease in rise time. [ 37–39 ] Combining the observation of voltage instability during detector operation (Figure 2 and Figure S1, Supporting Information) and the large temperature dependent rise time changes in Figure 3, we attribute the slow detector rise time to the ion migration induced charge trapping, which is greatly suppressed once the temperature is lowered.…”