Competition of Carrier Kinetics Contributes to Amplified Spontaneous Emission in Quasi-2D/3D (PBA)₂MA_n–1Pb_nBr_3n+1 Thin Films under Strip Light Mode

Abstract

Quasi-2D halide perovskites have potential in lasing due to their amplified spontaneous emission (ASE) properties. The ASE of (PBA)2MA n–1Pb n Br3n+1 thin films has been confirmed by photoluminescence (PL) testing using stripe light excitation (SLE). The ASE threshold decreases with decreasing environmental temperature (T E) or increasing number of inorganic layers (n). Using the transient absorption technique, the Auger recombination and the cooling process of the high-activity carrier are accelerated with the decrease of n or T E. A new ASE mechanism is proposed where high-activity carriers directly emit photons under photon perturbation from adjacent sites, leading to the accumulation and amplification of emitted photons only in the SLE region for ASE to occur. In addition, the reduction of n promotes light scattering between nano-thin layers, which supports a rapid increase in the ASE signal after the ASE threshold is crossed.

Photophysics and Carrier Dynamics of Lasing in Quasi-2D Lead Halide Perovskites

“…Figure shows transient absorption data that exhibit three distinct features: (1) photobleaching (PB) (blue) centered near ∼532 nm, (2) a short-lived photoinduced absorption (PIA 1) (red) at longer wavelengths, and (3) a long-lived photoinduced absorption (PIA 2) (red) at shorter wavelengths. These features are common in perovskite transient absorption spectra. − …”

“…Even more remarkable is the extremely small nonradiative term γ EEA = 3.6 × 10 −13 cm 3 s −1 contrasted with more typical values of ∼10 −10 cm 3 s −1 . 40,46,49,50 The assumption of initial carrier density being linearly dependent on pump fluence implies complete conversion of the photons to the carriers and is, therefore, an overestimation of the actual number of carriers. This assumption carries over to the effective rate equation coefficients.…”