3 research outputs found
Optical Optimization of the TiO2 Mesoporous Layer in Perovskite Solar Cells by the Addition of SiO2 Nanoparticles
In this work, SiO2 nanoparticles (NPs) were integrated into the mesoporous TiO2 layer of a perovskite solar cell to investigate their effect on cell performance. Different concentrations of SiO2/ethanol have been combined in TiO2/ethanol to prepare pastes for the fabrication of the mesoporous layer with which perovskite solar cells have been fabricated. Addition of SiO2 NPs of 50 and 100 nm sizes produces an enhancement of cell performance mainly because of an improvement of the photocurrent. This increment is in good agreement with the theoretical predictions based on light scattering induced by dielectric SiO2 NPs. The samples using modified scaffolds with NPs also present a significant lower currentāpotential hysteresis indicating that NP incorporation also affects the ion accumulation at the perovskite interface, providing an additional beneficial effect. The results stress the importance of the appropriated management of the optical properties on further optimization of perovskite solar cell technology
Delayed Luminescence in Lead Halide Perovskite Nanocrystals
The
mechanism responsible for the extremely long photoluminescence (PL)
lifetimes observed in many lead halide perovskites is still under
debate. While the presence of trap states is widely accepted, the
process of electron detrapping back to the emissive state has been
mostly ignored, especially from deep traps as these are typically
associated with nonradiative recombination. Here, we study the photophysics
of methylammonium lead bromide perovskite nanocrystals (PNCs) with
a photoluminescence quantum yield close to unity. We show that the
lifetime of the spontaneous radiative recombination in PNCs is as
short as 2 ns, which is expected considering the direct bandgap character
of perovskites. All longer (up to microseconds) PL decay components
result from the rapid reversible processes of multiple trapping and
detrapping of carriers with a slow release of the excitation energy
through the spontaneous emission channel. As our modeling shows, the
trap (dark) and excitonic states are coupled by the trappingādetrapping
processes so that they follow the same population decay kinetics,
while a majority of excited carriers are in the dark state. The lifetime
of the PNCs delayed luminescence is found to be determined by the
depth of the trap states, lying from a few tens to hundreds meV below
the emitting excitonic state. The delayed luminescence model proposed
in this work can serve as a basis for the interpretation of other
photoinduced transient phenomena observed in lead halide perovskites
Two-Color Single-Photon Emission from InAs Quantum Dots: Toward Logic Information Management Using Quantum Light
In
this work, we propose the use of the Hanbury-Brown and Twiss
interferometric technique and a switchable two-color excitation method
for evaluating the exciton and noncorrelated electronāhole
dynamics associated with single photon emission from indium arsenide
(InAs) self-assembled quantum dots (QDs). Using a microstate master
equation model we demonstrate that our single QDs are described by
nonlinear exciton dynamics. The simultaneous detection of two-color,
single photon emission from InAs QDs using these nonlinear dynamics
was used to design a NOT AND logic transference function. This computational
functionality combines the advantages of working with light/photons
as input/output device parameters (all-optical system) and that of
a nanodevice (QD size of ā¼20 nm) while also providing high
optical sensitivity (ultralow optical power operational requirements).
These system features represent an important and interesting step
toward the development of new prototypes for the incoming quantum
information technologies