Persistent Photoluminescence Superlinearity Beyond Static Recombination Physics in Metal Halide Perovskites.

Persistent intermediate power-law exponent (β) values in metal halide perovskites commonly occur across excitation regimes in which assignment to a single carrier-population recombination limit becomes ambiguous. Their strong dependence on excitation conditions further indicates that excitation-dependent photoluminescence cannot always be interpreted uniquely through a static Shockley-Read-Hall (SRH)-bimolecular-Auger recombination picture. Here, power-dependent and time-resolved photoluminescence measurements on methylammonium lead iodide (MAPbI3, MA = CH3​NH3) thin films reveal correlated evolution of excitation scaling, delayed emission, and illumination-history response under conditions that systematically modify vibrational dissipation and carrier-relaxation pathways. These behaviors are described using a dual-channel framework in which transient vibrational energy retention contributes to delayed radiative response. The results support an interpretation of PL superlinearity as an emergent, condition-dependent response associated with coupled carrier-lattice relaxation dynamics, rather than a simple transition between fixed recombination-order limits. More broadly, these results show that β and photoluminescence quantum yield (PLQY) should not be treated as fixed intrinsic material constants, but as excitation-conditioned observables shaped by the evolving relaxation environment, highlighting limitations in interpreting PL scaling laws as direct indicators of recombination pathways in soft semiconductors.