Ultrafast Hot‐Carrier Cooling in CsPbBr ₃ Supercrystals via Long‐Range Electronic Coupling

ABSTRACT Lead halide perovskite (LHP) nanocrystals (NCs) exhibit prolonged hot carrier (HC) cooling, which benefits photovoltaics but hinders light‐emitting applications. Current strategies to modulate HC dynamics often compromise intrinsic material properties or introduce competing photophysical processes. Here, we demonstrate that long‐range electronic coupling in CsPbBr ₃ supercrystals (SCs) efficiently accelerates HC cooling across different excitation regimes, enabling cooling dynamics approaching the prediction of the longitudinal optical phonon model. Owing to enhanced electronic density of states arising from cooperative interactions, transient absorption (TA) spectroscopy reveals SCs enable HC cooling that is twice as fast as isolated nanocrystals (NCs) at low carrier densities (2 × 10 ¹⁷ cm ⁻³ ). Remarkably, under high excitation densities (4.3 × 10 ¹⁸ cm ⁻³ ), carrier delocalization within the superlattices further weakens the spatial confinement‐induced Auger heating, accelerating HC cooling by over an order of magnitude. This work establishes SCs as a fresh platform to manipulate HC cooling.