Femtosecond Excitonic Relaxation Dynamics of Perovskite on Mesoporous Films of Al2O3 and NiO Nanoparticles†
We thank Prof. Teng-Ming Chen of NCTU for support of the steady-state PL measurements. Ministry of Science and Technology of Taiwan and Ministry of Education of Taiwan provided support for this project.
Graphical Abstract
Femtosecond optical gating (FOG) technique was employed to investigate the excitonic relaxation mechanism in a NiO-supported p-type perovskite. The effect of photoluminescence quenching and the excellent photovoltaic performance were rationalized based on this measurement.
Abstract
The excitonic relaxation dynamics of perovskite adsorbed on mesoporous thin films of Al2O3 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 non-emissive surface state larger than through the direct electronic relaxation channel, which quenches the PL intensity more effectively than on the Al2O3 film. We conclude that perovskite is an effective hole carrier in a p-type electrode for NiO-based perovskite solar cells showing great performance.
