Photoluminescence Emitter with 100% Power Efficiency─The Key Role of the Absorption Edge in CsPbBr ₃ Perovskite Quantum Dots

quantum dots (QDs). The samples were optimized by ligand engineering and controlled aging over the span of several months. Absorption edge changes reveal that the aging causes self-healing of intraband defect states that are otherwise contributing to a decrease of the PL quantum yield. In the optimized samples, we observed PL quantum yield reaching 100% and the PL power efficiency also approaching unity. This result means that all the absorbed excitation light energy is reemitted as luminescence. For the excitation wavelength of 532 nm, the emitted light energy comprises ∼ 80% of anti-Stokes PL and 20% of Stokes-shifted PL, while for the wavelength of 543 nm, the emission is composed entirely of anti-Stokes PL. These parameters are promising for many potential advanced applications, such as radiative cooling.