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Raman spectroscopic determination of hole concentration in undoped GaAsBi
摘要： Raman spectra of the undoped GaAs1-xBix (0<x<0.037) grown on GaAs by molecular beam epitaxy were investigated. With an increase of Bi component, we find that the longitudinal optical phonon-hole-plasmon-coupled (LOPC) mode first appears in the vicinity of the unscreened longitudinal optical (ULO) phonon frequency, and then shifts towards near the transverse optical (TO) phonon frequency. A new vibrational modes (~287 cm-1) between the TO and the ULO phonons was verified by use of low temperature polarized Raman measurement and the corresponding scattering intensities are found to be linearly proportional to the composition of Bi in GaAsBi. The hole concentrations determined by using the LOPC/ULO Raman intensities ratio increase from ~6.5×1016 to ~2.8×1017 cm -3 with Bi content and the measured results are in agreement with Hall measurements. Furthermore, the influence of excitation laser power on the estimation of the hole densities is discussed with the help of power dependent Raman spectroscopy.
关键词： Hall measurements,LO-phonon-plasmon–modes,Raman Spectroscopy,GaAsBi,Hole density
更新于2025-09-23 15:21:21
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Room Temperature Processed Transparent Cu-Zn-S Nanocomposites as Hole Transport Materials in CdTe Photovoltaics
摘要： Here, we report room temperature processed Cu-Zn-S ternary thin films fabricated using SILAR method as a back-contact hole transport layer in cadmium telluride (CdTe) solar cells. These Cu-Zn-S films are transparent to visible region with compact grains, and high conductivity. X-ray diffraction (XRD) measurements shows the crystalline nature of the as-deposited Cu-Zn-S films. The Cu-Zn-S nanocomposite as a back contact buffer layer in CdTe devices improves the device performance to 12.7% (average 12.4%) from 10.4% (average 9.8%) compared to a Au only back contact and is comparable to Cu/Au back contact (thermally evaporated). The temperature dependence current voltage characteristics shows the reduced back barrier height compared to Au only and Cu/Au back contact.
关键词： SILAR,Cu-Zn-S,back contact,hole transport layer (HTL),solar cells
更新于2025-09-23 15:21:01
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Hydroxymethyl Functionalized PEDOT-MeOH:PSS for Perovskite Solar Cells
摘要： Poly(hydroxymethylated-3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT-MeOH:PSS) conducting polymers are synthesized and incorporated in inverted structured perovskite solar cells (PVSCs) as hole transport materials. The highest occupied molecular orbital of PEDOT-MeOH is lowered by adding a hydroxymethyl (-MeOH) functional group to ethylenedioxythiophene (EDOT), and thus the work function of PEDOT-MeOH:PSS is increased. Additionally, hydrogen bonding can be formed among EDOT-MeOH monomers and between EDOT-MeOH monomers and sulfate groups on PSS, which promote PEDOT-MeOH chain growth and enhance PSS doping. The electronic, microstructural, and surface morphological properties of PEDOT-MeOH:PSS are modified by changing the amount of PSS and ferric oxidizing agent used in the polymerization and by adding ethylene glycol in the post-synthesis treatment. The PVSCs based on ethylene glycol treated PEDOT-MeOH:PSS overperform the PVSCs based on commercial PEDOT:PSS because of the better energetic alignment and the enhancement of PEDOT-MeOH:PSS electrical conductivity. This work opens the way to develop new hole transport materials for highly efficient inverted PVSCs.
关键词： hole transport material,perovskite,solar cell,electrical conductivity,work function
更新于2025-09-23 15:21:01
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Reducing Anomalous Hysteresis in Perovskite Solar Cells by Suppressing Interfacial Ferroelectric Order
摘要： Despite booming researches in organometal halide perovskite solar cells (PSCs) of recent years, considerable roadblocks remain for their large-scale deployment, ranging from undesirable current-voltage hysteresis to inferior device stability. Among various plausible origins of the hysteresis, interfacial ferroelectricity is particularly intriguing and warrants a close scrutiny. Here, we examine interfacial ferroelectricity in MAPbI3 (FAPbI3)/TiO2 and MAPbI3/PCBM heterostructures, and explore the correlations between the interfacial ferroelectricity and the hysteresis from the perspective of nonadiabatic electronic dynamics. It is found that ferroelectric order develops at the MAPbI3/TiO2 interface owing to the interaction between the polar MA ions and TiO2. The polarization switching of the MA ions under an applied gate field would result in drastically different rates in interfacial photoelectron injection and electron-hole recombination, contributing to the undesirable hysteresis. In a sharp contrast, ferroelectricity is suppressed at the FAPbI3/TiO2 and MAPbI3/PCBM interfaces, thanks to elimination of the interfacial electric field between perovskite and TiO2 via substitution of strong polar MA (dipole moment: 2.29 Debye) by weak polar FA ions (dipole moment: 0.29 Debye) and interface passivation, leading to consistent interfacial electronic dynamics and the absence of the hysteresis. The present work sheds light to the physical cause for hysteresis and points to the direction to which the hysteresis could be mitigated in PSCs.
关键词： Ferroelectricity,Hysteresis,Perovskite Solar Cells,Excited-state Electronic Dynamics,Electron-Hole Recombination,Orientation Selectivity
更新于2025-09-23 15:21:01
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Anthradithiophene based hole-transport material for efficient and stable perovskite solar cells
摘要： A novel hole-transport material (HTM) based on an anthradithiophene central bridge named BTPA-7 is developed. In comparison to spiro-OMeTAD (2,2’,7,7’-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9’-spirobifluorene), the synthetic steps of BTPA-7 are greatly reduced from 6 to 3 and the synthetic cost of BTPA-7 is nearly a half that of spiro-OMeTAD. Moreover, BTPA-7 exhibits a relatively lower conductivity but higher hole mobility and higher glass transition temperature (Tg) than spiro-OMeTAD. Compared with the photovolatic performance for spiro-OMeTAD, FA0.85MA0.15PbI3 and MAPbI3 PSC devices based on BTPA-7 exhibit slightly lower PCEs with the values of 17.58% (18.88% for spiro-OMeTAD) and 11.90% (13.25% for spiro-OMeTAD), respectively. Nevertheless, a dramatically higher Jsc of PSC based on BTPA-7 is achieved, which arises from the higher hole mobility of BTPA-7. In addition, the relatively hydrophobic character of BTPA-7 eventually enhances the PSC device stability. Lower cost, higher hole mobility, higher Tg, satisfactory photovoltaic performance, and superior device stability of BTPA-7 can be utilized as a substitute for spiro-OMeTAD in PSCs.
关键词： Stability,Anthradithiophene,Hole-transport material,Synthetic cost
更新于2025-09-23 15:21:01
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Facile synthesis of a??lucky clovera?? hole-transport material for efficient and stable large-area perovskite solar cells
摘要： Hole-transporting materials (HTMs) play a vital role of transporting holes from the perovskite layer to the counter electrode in perovskite solar cells (PSCs). A novel HTM BTPA-8 is feasibly synthesized by incorporating four dimethoxytriphenylamine leaflets and anthracene-based central bridge. BTPA-8 exhibits a suitable band alignment with MAPbI3 (MA ? CH3NH3) or FA0.85MA0.15PbI3 (FA?HC(NH2)2), high hole mobility, and high thermal stability. The best FA0.85MA0.15PbI3 device based on BTPA-8 exhibits a power conversion efficiency (PCE) of 17.99% in the reverse scan with an aperture area of 0.09 cm2. Under the same condition, a PCE of 18.92% is achieved by the solar cell based on the standard spiro-OMeTAD (2,2,7,7-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9-spirobifluorene). A comparable PCE of 12.31% is also obtained for BTPA-8 based MAPbI3 device compared with spiro-OMeTAD (13.25%) with an aperture area >1 cm2. BTPA-8 based PSCs exhibit better long-term stability than spiro-OMeTAD due to its high hydrophobicity. A lower synthesis cost of BTPA-8 than that of spiro-OMeTAD along with the elevated long-term stability makes it promising for application in PSCs.
关键词： Perovskite solar cells,Hole-transporting material,Anthracene,Low cost
更新于2025-09-23 15:21:01
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Enhanced stability and efficiency in inverted perovskite solar cells through graphene doping of PEDOT:PSS hole transport layer
摘要： Poly(3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) plays a relevant role in the device performance as hole extraction layer (HTL) of inverted perovskite solar cells. Here, we show a simple low-temperature spin coating method for obtaining homogenous graphene-doped thin films of PEDOT:PSS with improved electrical conductivity without decreasing optical transmittance. Moreover, the crystallinity and stability in ambient conditions of the perovskite grown on it are enhanced. The hydrophobic character of graphene probably blocks undesirable reactions hampering degradation. By impedance spectroscopy it is demonstrated better charge extraction and reduction of recombination mechanisms at the doped-HTL/perovskite interface, resulting in improved photovoltaic parameters of the solar cell and greater stability at room operation conditions thus providing a simple and cost-effective method of preparing solar cells based on hybrid perovskites.
关键词： perovskite solar cell,PEDOT:PSS,doping,graphene,hole transport layer,impedance spectroscopy
更新于2025-09-23 15:21:01
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The influence of acoustic deformation on the recombination radiation in InAs/GaAs heterostructure with InAs quantum dots
摘要： In the framework of electron-deformation model, the influence of deformation on the energy spectrum of electrons and holes in InAs/GaAs heterostructure with InAs quantum dots (QD) is investigated. The influence of acousto-electronic effects on the modulation of radiation energy at the recombination transition between the ground states of electron and hole in InAs/GaAs heterostructure with InAs quantum dots is investigated. The nature of the amplitude dependence of the modulation of the recombination radiation energy on the QD size and the amplitude of the mechanical stress created by the acoustic wave on the surface of the matrix is established.
关键词： Deformation,Modulation of the energy,Acoustic wave,Quantum dot,Energy of electron and hole
更新于2025-09-23 15:21:01
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A Dopanta??Free Hole Transporting Layer for Efficient and Stable Planar Perovskite Solar Cells
摘要： Hybrid organic-inorganic perovskites are attractive materials for the fabrication of efficient thin film solar cells. In order to make perovskite solar cells (PSCs) suitable for commercialization, stability issue should be addressed properly. In this work, we introduce a new dopant-free organic material, PV2000, as a stable hole transporting layer (HTL) for the fabrication of stable and efficient PSCs. For this purpose, we fabricate planar PSCs using a triple-A cation perovskite composition and replace commonly used 2,2′,7,7′ -Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD) HTL by dopant-free PV2000 polymer. Our characterization results disclose that the PV2000 has a great thermal stability, good hole mobility and suitable band alignment that well-matched with the valence band of triple-A cation perovskite. After proper optimization of PV2000 film thickness, we achieve a planar PSC with a maximum power conversion efficiency (PCE) of 18.93%, which is comparable with the spiro-based device (19.62%). Moreover, we further improve the PCE of the PV2000 based device up to 20.5% using a band alignment engineering by deposition thin layer of polyvinylpyrrolidone (PVP) at perovskite/HTL interface. More importantly, we find that the thermal, moisture and operational stabilities of the PSCs with PV2000 HTL are improved drastically as compared to the spiro-based devices, where the PSC with PV2000 retains ~88% of its initial PCE value under continuous illumination for 250 h as compared to the spiro-based one (39%).
关键词： efficiency,PV2000,stability,Perovskite solar cell,Hole transporting layer
更新于2025-09-23 15:21:01
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Recent progress on narrow-linewidth crystalline bulk Raman lasers
摘要： Narrow-linewidth, solid-state Raman lasers are of signi?cant importance for numerous applications. In last decade, variety of methods have been utilized to suppress the spectral linewidth of Raman laser output. In this review we summarize the recent works of narrow-linewidth and/or single-frequency solid-state Raman lasers. The mechanisms and results are addressed while the positive and negative aspects of each technique are also discussed to give the readers a reference to choose a proper narrow-linewidth method for certain applications.
关键词： F-P etalon,Injection seeding,Narrow-linewidth laser,Single-frequency laser,Raman laser,Spatial hole burning
更新于2025-09-23 15:21:01