2 research outputs found
Ultralong Radiative States in Hybrid Perovskite Crystals: Compositions for Submillimeter Diffusion Lengths
Organic–inorganic
hybrid perovskite materials have recently
evolved into the leading candidate solution-processed semiconductor
for solar cells due to their combination of desirable optical and
charge transport properties. Chief among these properties is the long
carrier diffusion length, which is essential to optimizing the device
architecture and performance. Herein, we used time-resolved photoluminescence
(at low excitation fluence, 10.59 μJ·cm<sup>–2</sup> upon two-photon excitation), which is the most accurate and direct
approach to measure the radiative charge carrier lifetime and diffusion
lengths. Lifetimes of about 72 and 4.3 μs for FAPbBr<sub>3</sub> and FAPbI<sub>3</sub> perovskite single crystals have been recorded,
presenting the longest radiative carrier lifetimes reported to date
for perovskite materials. Subsequently, carrier diffusion lengths
of 107.2 and 19.7 μm are obtained. In addition, we demonstrate
the key role of the organic cation units in modulating the carrier
lifetime and its diffusion lengths, in which the defect formation
energies for FA cations are much higher than those with the MA ones
Inside Perovskites: Quantum Luminescence from Bulk Cs<sub>4</sub>PbBr<sub>6</sub> Single Crystals
Zero-dimensional
perovskite-related structures (0D-PRS) are a new
frontier of perovskite-based materials. 0D-PRS, commonly synthesized
in powder form, manifest distinctive optical properties such as strong
photoluminescence (PL), narrow emission line width, and high exciton
binding energy. These properties make 0D-PRS compelling for several
types of optoelectronic applications, including phosphor screens and
electroluminescent devices. However, it would not be possible to rationally
design the chemistry and structure of these materials, without revealing
the origins of their optical behavior, which is contradictory to the
well-studied APbX<sub>3</sub> perovskites. In this work, we synthesize
single crystals of Cs<sub>4</sub>PbBr<sub>6</sub> 0D-PRS, and investigated
the origins of their unique optical and electronic properties. The
crystals exhibit a PL quantum yield higher than 40%, the highest reported
for perovskite-based single crystals. Time-resolved and temperature
dependent PL studies, supported by DFT calculations, and structural
analysis, elucidate an emissive behavior reminiscent of a quantum
confined structure rather than a typical bulk perovskite material