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Bi-Exciton Dissociation Dynamics in Nano-Hybrid Au-CuInS <sub/>2</sub> Nanocrystals
摘要： Multiexciton harvesting from semiconductor quantum dot has been a new approach for improving the solar cell efficiency in Quantum Dot Sensitized Solar Cells (QDSC). Till date, relation between multiexciton dissociation in metal?semiconductor nanohybrid system and boosting the power conversion efficiency (PCE) of QDSC were never discussed. Herein we report a detailed spectroscopic investigation of biexciton dissociation dynamics in copper indium sulfide (CuInS2, also referred as CIS) and Au-CIS nanohybrid, utilizing both time-resolved PL and ultrafast transient absorption (TA) techniques. Ultrafast transient absorption suggests the formation of bi-exciton in CIS NCs which efficiently dissociates in Au-CIS nanohybrids. Maximum multiexciton dissociation (MED) efficiency is determined to be ~ 80% at higher laser fluency, however it was observed to be 100% at lower laser fluency. Prior to exciton dissociation electrons are captured by Au NP in the nanohybrid from the conduction band of CIS NCs which is energetically higher than Fermi level of Au. Here we demonstrate the proof-of-concept in multi-electron dissociation which may provide a new approach for improving the efficiency in QDSSCs, where we found power conversion efficiency (PCE) of Au-CIS nanohybrids up to 2.49% as compared to ~1.06% ~for pure CIS NCs in similar condition. This finding can be an efficient approach towards the design and development of efficient solar cell and optoelectronic devices using the principles of multiexciton generation and extracting multiexcitons in metal-semiconductor nanohybrid system.
关键词： copper indium sulfide,biexciton dissociation dynamics,Quantum Dot Sensitized Solar Cells,power conversion efficiency,ultrafast transient absorption,Multiexciton harvesting,Au-CIS nanohybrid
更新于2025-09-23 15:21:21
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Photocarrier relaxation pathway in selenium quantum dots and its application for UV-Vis photodetecting
摘要： Chain-like materials have recently attracted significant attention due to their unique structure and outstanding electro-optical properties. However, the photocarrier dynamics and pathways in these materials that determine the electro-optical performances of the prepared devices have barely been touched. Herein, one typical chain-like materials e quantum dots (Se QDs) were prepared via a facile liquid phase exfoliation approach. The photocarrier dynamics in selenium quantum dots were systematically investigated via ultrafast transient absorption spectroscopy in the ultraviolet-visible regime. Four photocarrier decay pathways with different lifetime times were firstly detected, endues the elucidation and reconstruction of the energy schematic diagram of Se QDs. Thanks to the broadband photo-response and fast recovery time of Se QDs, a photoelectrochemical (PEC)-typed photodetector was proposed for the first time to our knowledge, demonstrating excellent photodetection properties. Considering the feasible fabrication method and clear photocarrier pathways, the excellent photocurrent density and stability of this photodetector undoubtedly guarantee the promising of selenium for advanced photonics devices.
关键词： broadband photo-response,photocarrier dynamics,ultrafast transient absorption spectroscopy,selenium quantum dots,photoelectrochemical photodetector
更新于2025-09-23 15:19:57
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Extent of Shallow/Deep Trap States beyond the Conduction Band Minimum in Defect-Tolerant CsPbBr <sub/>3</sub> Perovskite Quantum Dot: Control over the Degree of Charge Carrier Recombination
摘要： Perovskite quantum dots (PQDs) are known to be defect tolerant possessing clean band-gap with optically inactive benign defect states. However, we show that there exists significant deep trap states beyond conduction band minimum, although the extent of shallow trap states is observed to be minimal. Extent of deep trap states beyond conduction band minimum seem to significant in PQD, however the extent is less than even optically robust CdSe and InP based core/alloy-shell QDs. In-depth analyses based on ultrafast transient absorption and ultrasensitive single particle spectroscopic investigations decode the underlying degree of charge carrier recombination in CsPbBr3 PQD which are quite important for energy applications.
关键词： Perovskite quantum dots,ultrafast transient absorption,defect tolerant,single particle spectroscopy,charge carrier recombination,trap states
更新于2025-09-19 17:13:59
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Disentangling the Electron and Hole Dynamics in Janus CdSe/PbSe Nanocrystals through Variable Pump Transient Absorption Spectroscopy
摘要： CdSe/PbSe Janus hetero-nanocrystals (HNCs) represent an interesting system where structurally immiscible CdSe and PbSe co-exist in a single structure with intermixed electronic states. Here, we have investigated the carrier dynamics in Janus CdSe/PbSe HNCs through ultrafast transient absorption spectroscopy by selectively exciting either the CdSe or the PbSe domains. Upon excitation of the CdSe domain sub-picosecond hole transfer to the hybrid interfacial PbSe states were identified. On the other hand, the transfer of hot electron from PbSe to CdSe was evident upon creation of hot electrons in PbSe domain without exciting the CdSe domain. The photo-excited hot hole also gets transferred to the hybrid interfacial states in sub-ps time (~1ps) bleaching the corresponding transition. The decay of the localized hole was found to be much slower compared to the electron which can be beneficial for carrier extraction and multiexciton generation. The finding of hot electron transfer in a single structure and slow decay of holes can thus prove to be advantageous for future design of photovoltaic devices.
关键词： carrier dynamics,ultrafast transient absorption spectroscopy,CdSe/PbSe Janus hetero-nanocrystals,photovoltaic devices,hot electron transfer
更新于2025-09-10 09:29:36