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Core/Shell Nanocrystal Tailored Carrier Dynamics in Hysteresis-Less Perovskite Solar Cell with ~20% Efficiency and Long Operational Stability
摘要： The ambient stability, hysteresis and trap states in organo-halide perovskite solar cells (PSCs) are correlated to the influence of interlayer interfaces and grain boundaries. Astute incorporation of Cu2ZnSnS4 (CZTS) and Au/CZTS core/shell nanocrystals (NCs) can achieve the goal of simultaneously achieving better performance and ambient stability of the PSCs. With optimized Au/CZTS NC size and concentration in the photoactive layer, power conversion efficiency can be increased up to 19.97±0.6% with ambient air stability ?800 h, as compared to 14.46±1.02% for the unmodified devices. Through efficient carrier generation by CZTS and perovskite, accompanied by the plasmonic effect of Au, carrier density is sufficiently increased as validated from transient absorption spectroscopy. NCs facilitate the interfacial charge transfer by suitable band alignment, and removal of recombination centers such as metallic Pb0, surface defects or impurity sites. NC-embedding also increases the perovskite grain size and assist in pin-hole filling, reducing the trap state density.
关键词： Carrier Dynamics,Perovskite Solar Cells,Plasmonics,Optoelectronics,Energy Conversion and Storage,Operational Stability,Hysteresis-Less,Core/Shell Nanocrystals
更新于2025-09-12 10:27:22
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Enhancement of Open‐Circuit Voltage of Perovskite Solar Cells by Interfacial Modification with <i>p</i> ‐Aminobenzoic Acid
摘要： Various approaches of interface engineering are shown to be effective in improving the device performance of organic–inorganic hybrid perovskite solar cells (PSCs). The modification of the photoactive layer of PSC, CH3NH3PbI3 (MAPbI3), by spin-coating a layer of p-aminobenzoic acid (PABA), which can significantly enhance the open-circuit voltage (VOC), the fill factor (FF), and the power conversion efficiency (PCE) of PSCs, is herein reported. The champion device shows a short-circuit current ( JSC) of 22.83 mA cm?2, VOC of 1.167 V, FF of 0.768, and PCE of 20.47%. The improvement in photovoltaic performance is attributed to the suppression of carrier trap states and the improvement in the morphologies of perovskite films. This work demonstrates a simple and effective protocol to enhance the device performance, and provides an insight into the influence of PABA post-treatment on the charge carrier dynamics.
关键词： carrier dynamics,interface engineering,p-aminobenzoic acid,postdeposition treatment,organic–inorganic hybrid perovskite
更新于2025-09-11 14:15:04
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Charge Carrier Dynamics in Electron-Transport-Layer-Free Perovskite Solar Cells
摘要： Better understanding the carrier dynamics process in electron transport layer (ETL) -free perovskite solar cells (PSCs) enables the further exploration of the perovskite potential and corresponding device structure design. Herein, ETL-free perovskite/transparent conductive film SnO2:F(FTO) contact with different perovskite thickness illuminated by varied light intensity was investigated by scanning probe microscopy technology. Strong charge transfer is occurred at the perovskite/FTO contact, evidenced by the variations of both surface contact potential and local current value. Mott-Schottky analysis based on capacitance-voltage measurements suggests that the interface property of perovskite/FTO contact is similar to the perovskite/TiO2/FTO structure, make it ideal to fabricate ETL-free PSCs. The cross-sectional surface potential drop was found to be mainly located at the CH3NH3PbI3/FTO heterojunction, suggesting a single diode junction in the ETL -free PSCs. Furthermore, a single-side abrupt p-n++ junction model is employed to illustrate the energy level alignment at the perovskite/FTO contact. This study will be helpful for understanding the carrier dynamics process and thus achieving high device efficiency in the ETL-free PSCs.
关键词： perovskite solar cells,Carrier dynamics,surface potential,scanning probe microscopy,heterojunction
更新于2025-09-11 14:15:04
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Carrier Dynamics in SnS<inf>2</inf> Single Crystals and Vertical Nanostructures: Role of Edges
摘要： SnS2 is a member of the van der Waals 2D layered materials family. Its moderate bandgap, environmental stability and high carrier mobility makes it attractive for solar energy conversion application. We explore how nanostructuring SnS2 in the form of vertically-aligned nanoflakes to increase the surface area impacts the lifetime and microscopic conductivity of photoinjected carriers compared to the bulk SnS2. Increased surface area and the presence of edges is beneficial to the efficiency of SnS2 photoanode performance but it comes at a cost of increased carrier trapping at surface and edge states.
关键词： THz spectroscopy,van der Waals materials,SnS2,carrier dynamics,nanostructuring
更新于2025-09-11 14:15:04
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Reconstructing charge-carrier dynamics in porous silicon membranes from time-resolved interferometric measurements
摘要： We performed interferometric time-resolved simultaneous reflectance and transmittance measurements to investigate the carrier dynamics in pump-probe experiments on thin porous silicon membranes. The experimental data was analysed by using a method built on the Wentzel-Kramers-Brillouin approximation and the Drude model, allowing us to reconstruct the excited carriers’ non-uniform distribution in space and its evolution in time. The analysis revealed that the carrier dynamics in porous silicon, with ~50% porosity and native oxide chemistry, is governed by the Shockley-Read-Hall recombination process with a characteristic time constant of 375 picoseconds, whereas diffusion makes an insignificant contribution as it is suppressed by the high rate of scattering.
关键词： carrier dynamics,porous silicon,Drude model,Shockley-Read-Hall recombination,interferometric measurements
更新于2025-09-11 14:15:04
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Investigation on the effect of indium composition on ultrafast carrier dynamics in InGaN alloys
摘要： In this letter, we investigated the effect of indium composition on carrier relaxation mechanisms in InGaN alloys. Four high quality alloys with indium composition from 25% to 75% were fabricated using energetic neutral atomic-beam lithography/epitaxy molecular beam epitaxy. Using sub-picosecond resolved photoluminescence at high carrier density, it was found the effective carrier lifetime extends with increasing indium composition. Moreover, the calculated initial carrier temperature also rises with higher indium composition. These results are consistent with the theoretical prediction that a greater phonon bandgap could reduce the carrier cooling rate to a certain extent via hot carrier bottleneck effect.
关键词： InGaN alloys,indium composition,carrier dynamics,photoluminescence,molecular beam epitaxy
更新于2025-09-10 09:29:36
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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
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Ultrafast THz photophysics of solvent engineered triple-cation halide perovskites
摘要： Solution processed thin film organic-inorganic perovskites are key to the large scale manufacturing of next generation wafer scale solar cell devices. The high efficiency of the hybrid perovskite solar cells is derived mainly from the large carrier mobility and the charge dynamics of films, which heavily depend on the type of solvent used for the material preparation. Here, we investigate the nature of conduction and charge carrier dynamics of mixed organic-inorganic cations [methylammonium (MA), formamidinium (FA), and cesium (Cs)] along with the mixed halides [iodine (I) and bromine (Br)] perovskite material [Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3] synthesized in different solvents using optical pump terahertz probe (OPTP) spectroscopy. Our findings reveal that carrier mobilities and diffusion lengths strongly depend on the type of solvent used for the preparation of the mixed cation perovskite film. The mixed cation perovskite film prepared using dimethylformamide/dimethylsulfoxide solvent shows greater mobility and diffusion length compared to γ-butyrolactone solvent. Our findings provide valuable insights to improve the charge carrier transport in mixed cation perovskites through solvent engineering.
关键词： charge carrier dynamics,OPTP spectroscopy,diffusion length,perovskites,carrier mobility,solvent engineering
更新于2025-09-09 09:28:46
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Electronic Traps and Phase Segregation in Lead Mixed-Halide Perovskite
摘要： An understanding of the factors driving halide segregation in lead mixed-halide perovskites is required for their implementation in tandem solar cells with existing silicon technology. Here we report that the halide segregation dynamics observed in the photoluminescence from CH3NH3Pb(Br0.5I0.5)3 is strongly influenced by the atmospheric environment, and that encapsulation of films with a layer of poly(methyl methacrylate) allows for halide segregation dynamics to be fully reversible and repeatable. We further establish an empirical model directly linking the amount of halide segregation observed in the photoluminescence to the fraction of charge-carriers recombining through trap-mediated channels, and the photon flux absorbed. From such quantitative analysis we show that under pulsed illumination, the frequency of the modulation alone has no influence on the segregation dynamics. Additionally, we extrapolate that working CH3NH3Pb(Br0.5I0.5)3 perovskite cells would require a reduction of the trap-related charge-carrier recombination rate to (cid:46) 105 s?1 in order for halide segregation to be sufficiently suppressed.
关键词： photoluminescence,lead mixed-halide perovskites,halide segregation,charge-carrier dynamics,trap-mediated recombination
更新于2025-09-09 09:28:46
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Probing the upper band gap of atomic rhenium disulfide layers
摘要： Here, we investigate the ultrafast carrier dynamics and electronic states of exfoliated ReS2 films using time-resolved second harmonic generation (TSHG) microscopy and density functional theory (DFT) calculations. The second harmonic generation (SHG) of layers with various thicknesses is probed using a 1.19-eV beam. Up to ~13 nm, a gradual increment is observed, followed by a decrease caused by bulk interferometric light absorption. The addition of a pump pulse tuned to the exciton band gap (1.57 eV) creates a decay-to-rise TSHG profile as a function of the probe delay. The power and thickness dependencies indicate that the electron–hole recombination is mediated by defects and surfaces. The two photon absorptions of 2.38 eV in the excited state that are induced by pumping from 1.57 to 1.72 eV are restricted because these transitions highly correlate with the forbidden d–d intrasubshell orbital transitions. However, the combined usage of a frequency-doubled pump (2.38 eV) with wavelength-variant SHG probes (2.60–2.82 eV) allows us to vividly monitor the variations in TSHG profiles from decay-to-rise to rise-to-decay, which imply the existence of an additional electron absorption state (s-orbital) at an approximate distance of 5.05 eV from the highest occupied molecular orbital states. This observation was critically examined by considering the allowance of each electronic transition and a small upper band gap (~0.5 eV) using modified DFT calculations.
关键词： density functional theory,ReS2,time-resolved spectroscopy,ultrafast carrier dynamics,second harmonic generation
更新于2025-09-09 09:28:46