Femtosecond Excitonic Relaxation Dynamics of Perovskite on Mesoporous Films of Al₂O₃ and NiO Nanoparticles

Abstract

The excitonic relaxation dynamics of perovskite adsorbed on mesoporous thin films of Al 2 O 3 and NiO upon excitation at 450 nm were investigated with femtosecond optical gating of photoluminescence (PL) via up-conversion. The temporal profiles of emission observed in spectral region 670-810 nm were described satisfactorily with a composite consecutive kinetic model and three transient components representing one hot and two cold excitonic relaxations. All observed relaxation dynamics depend on the emission wavelength, showing a systematic time-amplitude correlation for all three components. When the NiO film was employed, we observed an extent of relaxation proceeding through the nonemissive surface state larger than through the direct electronic relaxation channel, which quenches the PL intensity more effectively than on the Al 2 O 3 film. We conclude that perovskite is an effective hole carrier in a p-type electrode for NiO-based perovskite solar cells showing great performance.

Highly efficient and stable planar perovskite solar cells with reduced graphene oxide nanosheets as electrode interlayer

“…Recently, nickel oxides have been demonstrated as an alternative to PEDOT:PSS as a hole-transporting layer in PeSCs with better energy-level alignments between CH 3 NH 3 PbI 3 perovskites and nickel oxides [22,23]. However, to achieve a reasonable PCE, the nickel oxide required either a high-temperature process or a vacuum-process and additional UV/O 3 treatment, which can nullify the solution-processible manufacturing of PeSC based on OPV structures.…”

Magneto‐Optical Studies on Spin‐Dependent Charge Recombination and Dissociation in Perovskite Solar Cells

“…The OMHPs can be considered as ferroelectrically semiconducting materials with dual spontaneous electric polarizations and photoexcited states . In such ferroelectric semiconducting materials the photoexcited excitons have very low binding energies ranging from 37 to 98 meV, which can cause a quick charge dissociation in picoseconds at room temperature . As a consequence, a photoexcitation can lead to a large number of free electrons and holes, due to the low binding energies and fast dissociation, to generate photocurrent .…”

“…Here, we explore room‐temperature magneto‐photoluminescence and magneto‐photocurrent from OMHPs to study the spin‐dependent charge dissociation and recombination in generating photocurrent. In general, the photogenerated electrons and holes can be captured to form electron–hole pairs due to Coulomb attractions when they arrive in their mutual capture radius . The recombined electron–hole pairs can generate two opposite outcomes: relaxing into excitons ready to generate photoluminescence and lasing actions at high excitation intensities, or dissociating into free carriers to produce photocurrent .…”

Optical, Excitonic, and Electronic Properties of CH3NH3PbI3 Thin Films and Their Application in Photovoltaics

“…At this time, the electrons in the conduction band and the holes in the valence band will form excitons. For CH 3 NH 3 PbI 3 absorbers, the lifetime of hot electrons is about 1 ps [28], and the exciton lifetime associated with the material structure is approximately 10-100 ns. Exciton binding energy is a very important parameter for the light absorption materials of photovoltaics.…”