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Implementation of data-cube pumpa??probe KPFM on organic solar cells
摘要： An implementation of pump–probe Kelvin probe force microscopy (pp-KPFM) is reported that enables recording the time-resolved surface potential in single-point mode or over a 2D grid. The spectroscopic data are acquired in open z-loop configuration, which simplifies the pp-KPFM operation. The validity of the implementation is probed by measurements using electrical pumping. The dynamical photoresponse of a bulk heterojunction solar cell based on PTB7 and PC71BM is subsequently investigated by recording point-spectroscopy curves as a function of the optical power at the cathode and by mapping 2D time-resolved images of the surface photovoltage of the bare organic active layer.
关键词： Kelvin probe force microscopy (KPFM),time-resolved measurements,bulk heterojunctions,organic photovoltaics,pump–probe configuration,photocarrier dynamics
更新于2025-09-16 10:30:52
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MOVPE-Grown Quantum Cascade Laser Structures Studied by Kelvin Probe Force Microscopy
摘要： A technique for direct study of the distribution of the applied voltage within a quantum cascade laser (QCL) has been developed. The detailed pro?le of the potential in the laser claddings and laser core region has been obtained by gradient scanning Kelvin probe force microscopy (KPFM) across the cleaved facets for two mid-infrared quantum cascade laser structures. An InGaAs/InAlAs quantum cascade device with InP claddings demonstrates a linear potential distribution across the laser core region with constant voltage drop across the doped claddings. By contrast, a GaAs/AlGaAs device with AlInP claddings has very uneven potential distribution with more than half of the voltage falling across the claddings and interfaces around the laser core, greatly increasing the overall voltage value necessary to achieve the lasing threshold. Thus, KPFM can be used to highlight design and fabrication ?aws of QCLs.
关键词： MOVPE,quantum cascade laser,Kelvin probe force microscopy
更新于2025-09-16 10:30:52
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Electroluminescence and contact formation of 1-(pyridin-2-yl)-3-(quinolin-2-yl)imidazo[1,5-a]quinoline thin films
摘要： Contact formation was investigated for the recently introduced organic light emitting molecule 1-(pyridin-2-yl)-3-(quinolin-2-yl)imidazo[1,5-a]quinoline (PCIC) by in situ atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM) during physical vapor deposition (PVD). The hole conductors poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and poly(9-vinylcarbazole) (PVK), as well as the electron conductor bathocuproine (BCP) were used. Different growth modes were found for PCIC films and charge carrier injection barriers were identified. Based on these findings, electroluminescent layer structures with an imidazo[1,5-a]quinoline were prepared for the first time and effects of contact formation on radiative recombination were studied. Depending on the chosen contact material, blue PCIC electroluminescence or significantly red-shifted emission presumably caused by electroplex formation could be obtained. Using PCIC in a host-guest system within a matrix of PVK and 1,3-bis[5-(4-tert-butylphenyl)-2-[1,3,4]oxadiazolyl]benzene (Oxd-7), led to blue emission at improved luminescence. The studied interactions of PCIC with typical contact materials reveal the potential and limitations to use PCIC as an electroluminescent material.
关键词： Kelvin probe force microscopy,Electroluminescence,Contact formation,Organic light-emitting diode
更新于2025-09-10 09:29:36
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Surface potential of meso-dimensional ZnS:Mn particles obtained using SHS method
摘要： The dependence of surface potential value on the particle size of micro- and meso-fractions for powdered ZnS:Mn obtained using self-propagating high-temperature synthesis has been investigated. Rather good agreement of model representations for the change in the value of surface potential for the particle with its size changed due to overlapping the space charge regions from opposite surfaces within the range ~ 1 ≤ R/Leff ≤ ~ 2.2 (R, particle radius; Leff, screening length) with experimental data obtained using the method of Kelvin probe microscopy has been shown. The value of Leff for ZnS:Mn particles is estimated as approximately 30 nm.
关键词： Surface potential,Nanoscale effects,ZnS:Mn,Particle size,Effective screening length,Kelvin probe force microscopy
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Space Charges in Metal-Solid Electrolyte-Metal Structures
摘要： The influence of electrodes on the space charge distribution in solid polymer electrolytes has been investigated. Aluminum-poly(ethylene oxide)-aluminum sample structures with varying distance between the metal electrodes are considered. The charge distribution in the poly(ethylene oxide) is extracted by differentiating twice the surface potential measured by the Kelvin Probe Force Microscopy. With this approach, charge oscillations and charge packets have been detected for the first time in solid electrolytes under biased and unbiased conditions.
关键词： Kelvin probe force microscopy,interface effects,space charges,solid electrolyte,charge distribution
更新于2025-09-09 09:28:46
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Surface potential and thin film quality of low work function metals on epitaxial graphene
摘要： Metal films deposited on graphene are known to influence its electronic properties, but little is known about graphene’s interactions with very low work function rare earth metals. Here we report on the work functions of a wide range of metals deposited on n-type epitaxial graphene (EG) as measured by Kelvin Probe Force Microscopy (KPFM). We compare the behaviors of rare earth metals (Pr, Eu, Er, Yb, and Y) with commonly used noble metals (Cr, Cu, Rh, Ni, Au, and Pt). The rare earth films oxidize rapidly, and exhibit unique behaviors when on graphene. We find that the measured work function of the low work function group is consistently higher than predicted, unlike the noble metals, which is likely due to rapid oxidation during measurement. Some of the low work function metals interact with graphene; for example, Eu exhibits bonding anomalies along the metal-graphene perimeter. We observe no correlation between metal work function and photovoltage, implying the metal-graphene interface properties are a more determinant factor. Yb emerges as the best choice for future applications requiring a low-work function electrical contact on graphene. Yb films have the strongest photovoltage response and maintains a relatively low surface roughness, ~5 nm, despite sensitivity to oxidation.
关键词： work function,Kelvin Probe Force Microscopy,photovoltage,rare earth metals,graphene
更新于2025-09-09 09:28:46
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Controlling the Phase Segregation in Mixed Halide Perovskite through Nanocrystal Size
摘要： Mixed halide perovskites are one of the promising candidates in developing solar cells and LEDs, among others applications due to their tunable optical properties. Nonetheless, photoinduced phase segregation, by forming segregated Br-rich and I-rich domains, limits the overall applicability. We tracked the phase segregation with increasing crystalline sizes of CsPbBr3-xIx and their photoluminescence under continuous-wave laser irradiation (405 nm, 10 mW cm-2), and observed the occurrence of the phase segregation from the threshold size of 46 ± 7 nm. This results have an outstanding agreement with the diffusion length (45.8 nm) calculated also experimentally from the emission lifetime, segregation rates. Furthermore, through Kelvin probe forced microscopy, we confirmed the correlation between the phase segregation and the reversible halide ion migration among grain center/boundaries. These results open a way to achieve segregation-free mixed halide perovskites and improve their performances in optoelectronic devices.
关键词： nanocrystal size,photoluminescence,phase segregation,Kelvin probe force microscopy,Mixed halide perovskites
更新于2025-09-09 09:28:46