Ultrafast Many-Particle Phenomena in Lead Bromide Hybrid Perovskite Nanocrystals Under Strong Optical Excitation

Abstract

In recent years, there has been a surge in research efforts to utilize organic−inorganic lead halide perovskites (OLHPs) in optoelectronic devices (e.g., concentrator photovoltaics) requiring high light illumination. Yet, knowledge of the physics of photocarriers in perovskites in the high-excitation regime is limited. Here, we investigate carrier and exciton dynamics that are manifested under strong light illumination in methyl ammonium lead bromide perovskite nanocrystals (NCs) using ultrafast pump-probe spectroscopy. We demonstrate that the carrier trapping process is highly excitation intensity dependent because of a potential barrier that isolates trap states from the band edge. At low excitation densities, holes are unable to cross the energy barrier, but holes undergo trapping at moderate densities (1018–1020 cm–3). The charge carrier trapping is negligible due to the dominance of higher-order Auger processes at high excitation density (>1020 cm–3). We suggest that the effect of trap states is likely to be insignificant for perovskite concentrator solar cells.

Ultrafast Exciton Trapping and Exciton–Exciton Annihilation in Large-Area CVD-Grown Monolayer WS2

“…Femtosecond broadband TA measuring system is based on a femtosecond Ti: Sapphire amplifier (wavelength ∼ 800 nm and pulse width < 35 fs). , The output from the amplifier (Spitfire Ace, Spectra physics) was divided into two components to generate pump and probe pulses. Pump pulses (at 610 and 532 nm) were obtained from the nonlinear optical parametric amplifier (TOPAS).…”

Vibrational study of lead bromide perovskite materials with variable cations based on Raman spectroscopy and density functional theory

“…Metal halide perovskites (MHP), in particular the trihalide perovskites, are a remarkable class of materials that have resulted in a rapid series of breakthroughs in the field of optoelectronic devices. [1][2][3][4][5][6] Over the past decades the MHPs have emerged as suitable materials for solar cells, light emitting diodes, lasers, transistors, and memory devices. [7][8][9][10][11][12][13] It has been demonstrated that MHP-based photovoltaic devices show power conversion efficiencies of more than 22%, [14,15] and the devices can be produced on cheap non-crystalline substrates by both vapor deposition and solution processing.…”

Slower Auger Recombination in 12-Faceted Dodecahedron CsPbBr3 Nanocrystals

“…Lead halide perovskite nanocrystals (PNCs) have shown exceptional promises in light emitting devices (LEDs) due to their high photoluminescence quantum yield (PLQY), wide tunable emission wavelength range, defect tolerance, and low-cost solution processability. − In the past few years, tremendous efforts such as compositional engineering (via doping and alloying), , surface reconstruction, , shape tuning, , and interfacial engineering , have been employed to fabricate efficient PNC based LEDs, which led to the significant enhancement in the external quantum efficiencies (EQEs) exceeding 20% . Even though the EQEs of PNCs are significantly enhanced, , still there are numerous complications associated with the device performances and operational stability including defects stemming from Br and Pb vacancies, detachment of ligands from the CsPbBr 3 surface, leading to a decrease in photoluminescence quantum yield (PLQY), and change of the morphology with time.…”