Perovskite laser maintains stable performance over 400 million pulses - Phys.org

Photon echo (PE) spectroscopy is a powerful technique for probing decoherence mechanisms and charge carrier dynamics in semiconductor systems. Beyond traditional coherence measurements, characterizing the photon statistics of the echo signal is important for assessing its potential in quantum information applications and understanding the underlying quantum mechanical processes. Here, we study the photon statistics of PE signals generated by excitons in ensembles of lead halide perovskite CsPbI3 nanocrystals at cryogenic temperature of 2 K using continuous-variable quantum state optical tomography based on homodyne detection. Pronounced Rabi oscillations of the PE amplitude allow us to evaluate the statistics for various pulse areas in the excitation sequence. The damping of the oscillations with increasing pulse area is attributed to spatial excitation inhomogeneity and excitation-induced dephasing. Despite the large ensemble of optically addressed excitons, the efficiency of generated PE signals is low which is attributed to the complex energy level structure of excitons and non-radiative recombination channels in CsPbI3 nanocrystals.

Researchers have uncovered a way to suppress halide segregation in tandem solar cells, improving both efficiency and stability. Their strategy works across multiple mixed-halide perovskite compositions, suggesting the approach may be broadly applicable to this important class of photovoltaic materials. Tandem solar cells stack two different light-absorbing materials on top of one another, allowing them to convert more sunlight into electricity than either material alone. Mixed-halide perovskites—crystals containing both iodide and bromide ions—are commonly used as the top layer because their composition can be tuned to absorb high-energy light while permitting longer wavelengths to pass through to the lower cell. However, because iodide and bromide crystallize at different rates, the resulting films tend to be uneven in composition, with bromide-rich regions forming near the surface.

In the modern information era, human-machine interaction is undergoing a profound transformation, making display one of the most important optoelectronic technologies1. The development of next-generation displays places increasing demands on light-emitting materials with high colour purity, high efficiency, and wide colour gamut to ensure faithful information delivery2,3. Compared with already-commercilised emitters such as phosphors, organic semiconductors, and quantum dots, metal halide perovskite nanocrystals have attracted particular attention because of their high photoluminescence quantum yields (PLQY), narrow emission linewidths and extremely strong absorption strengths, which enable excellent colour purity, efficient “photon recycling”, nearly full coverage of the Rec. 2020 colour gamut, and usefulness in “in-pixle” colour conversion, required for microdisplays4,5,6. Despite these advantages, their practical application remains constrained by intrinsic instability. Metal halide perovskite nanocrystals are nanoscale ionic semiconductors with an ABX3 chemical formula, consisting of monovalent organic or inorganic cations, divalent metal cations, and halide anions7.