Formation of Multiple Quantum Wells in 2D/3D Perovskite Heterostructures Invalidates Phonon Bottleneck Effect^†

The importance of the phonon bottleneck effect on the optoelectronic properties of organic-inorganic hybrid perovskites (OIHPs) has been well documented. While randomly distributed multiple quantum wells (MQWs) are frequently generated in 2D/3D perovskite heterostructures, the influence of MQWs formation in 2D/3D perovskite heterostructures on the phonon bottleneck effect is poorly understood. In this study, we construct 2D/3D perovskite heterostructures using 2D OIHP (NH₃(CH₂)₈NH₃PbI₄, OdAPbI₄) to passivate 3D OIHP (FAPbI₃) and investigate their excitons and carrier dynamics by employing photoluminescence (PL) spectroscopy and femtosecond optical-pump terahertz-probe spectroscopy (fs-OPTPS). We observe the formation of MQWs and establish a structure-dynamics-property relationship among the exciton formation time (T_EF), the hot carrier cooling rate (k_cool) and the effective charge-carrier mobility (ϕμ). The formation of MQWs could significantly invalidate the phonon bottleneck effect and modulate the optoelectronic properties of 2D/3D perovskite heterostructures. This work provides valuable information on the importance of band alignment and the phonon bottleneck effect in the strategy of 2D/3D perovskite heterostructures.