NIMSAWARD2025-abstracts

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A. Yamakata et al.,J PHOTOCHEM PHOTOBNOL C-PHOTOCHEM REV 40, 234 (2019).Pump: 500 nmProbe: 3395 cm-1 (2945 nm)FluencePump: 532 nmIncrease in absorption without vibrational structure due to injected electronsApplied to Perovskite(PS) LayerFAPbI₃（（ Formamidinium lead iodide ））Future PlanP1-5Probing Free Carriers (Electrons)42 Applied visible-pump mid infrared-probe transient Detected free-carrier absorption using infrared light. Confirmed electron injection from the perovskite layerabsorption to perovskite solar cells.to the PCBM layer. Determine the electron injection rate from perovskiteto PCBM by directly monitoring the PCBM molecules. Investigate the dependence of electron injection rateon LUMO levels of electron acceptors. Clarifying the relationship between electron injectionand perovskite layer stability.Key Words: femtosecond, vis-pump IR-probe, transient absorption spectroscopyKey Words: femtosecond, vis-pump IR-probe, transient absorption spectroscopyTheme underDiscussionDiscussion(FAPbI₃₃PSPCBM/PS)PSFemtosecond IR probeEarly Dynamics of Photoexcited CarriersUnderstanding the origins of conversion efficiency :Solar cell efficiency is governed by ultrafast carrier generation andrecombination, which critically influence charge collection duringlight-to-current conversion.Guiding material design and interface engineering:Visualization of initial processes reveals loss pathways, enablingrational design via material tuning and interface optimization.Toward improved stability:lifetimes and recombination pathways offersClarifying carrierinsights into photo-induced degradation mechanisms in perovskites,including ion migration and defect formation.Summaryfrom intraband transitions,facilitated by momentum relaxation through phonon and impurityscattering, with transition energies (~tens of meV) corresponding toinfrared photon energies (0.05–0.5 eV).Free-carrierabsorption originatesAbsorption of Injected Electrons Observed Only with Dye-to-TiO₂Electron InjectionUnderstanding ultrafast carrier processes such as generation, diffusion, and recombination iscrucial for improving the photovoltaic performance of perovskite materials. In this study,femtosecond visible pump–mid-infrared probe spectroscopy was employed to quantitativelytrace the temporal evolution of free carriers, aiming to elucidate their dynamics and providefundamental insights into enhancing photoelectric conversion efficiency.This study investigates the electron transfer process from the perovskite layer to the PCBMelectron transport layer, with electron injection times reported between sub-picoseconds andtens of picoseconds. The aim was to probe and clarify the electron transfer dynamics into thePCBM.Battery Materials Analysis Group, GREEN Hidenori NoguchiE-mail：： NOGUCHI.Hidenori@nims.go.jpVBM：ca. –5.5 eVCBM：ca. –4.0 eVEnergy Levels of PCBMLUMO：ca. –4.0 eV ~ –4.1 eVHOMO：ca. –6.0 eV1. Perovskite CB slightly above PCBM LUMO.2. Electrons transfer to PCBM after excitation.3. PCBM serves as electron transport layer.Electron injection from perovskite to PCBM monitored by VIS pump IR probesElectron Injection from Perovskite to PCBM Effect of Electron InjectionWhen electrons are injected into the LUMO of PCBM, theypartially occupy the carbonyl bonds, reducing their bond order. Expected ResultThe ν(C=O) vibrational frequency decreases (red shift)IR absorption intensity and peak shape also change.IntroductionUltrafast Carrier Dynamics in Perovskites Ultrafast Carrier Dynamics in Perovskites Probed by Femtosecond Visible–Mid-IR Probed by Femtosecond Visible–Mid-IR SpectroscopySpectroscopy..