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Insights from Device Modeling of Perovskite Solar Cells
摘要： In this perspective, we explore the insights into the device physics of perovskite solar cells gained from modeling and simulation of these devices. We discuss a range of factors that influence the modeling of perovskite solar cells, including the role of ions, dielectric constant, density of states, and spatial distribution of recombination losses. By focusing on the effect of non-ideal energetic alignment in perovskite photovoltaic devices, we demonstrate a unique feature in low recombination perovskite materials – the formation of an interfacial, primarily electronic, self-induced dipole that results in a significant increase in the built-in potential and device open-circuit voltage. Finally, we discuss the future directions of device modeling in the field of perovskite photovoltaics, describing some of the outstanding open questions in which device simulations can serve as a particularly powerful tool for future advancements in the field.
关键词： device physics,density of states,simulation,device modeling,recombination losses,dielectric constant,perovskite solar cells,energetic alignment
更新于2025-09-19 17:13:59
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Ammonium Fluoride Interface Modification for High Performance and Long‐Term Stable Perovskite Solar Cells
摘要： As a new generation of most promising photovoltaic device, perovskite solar cell (PSC) rapidly evolves its efficiency from 3.8% in 2009 to 24.02% very recent. Numerous studies indicate that interface defects and the recombination of charge carrier at interface remains an important research object, which hinders the improvement of photovoltaic performance and stability of PSCs. Herein, a novel method for modifying the interface between the electron transport layer and the perovskite layer by ammonium fluoride (NH4F) is presented. After the TiO2 film modified with NH4F, the TiO2/perovskite interface defects are mitigated and passivated, and the carrier recombination decrease and the electron extraction and injection capacity increase. Consequently, the planar PSC interfacial modified with an optimal NH4F concentration can maintain over 95% initial efficiency for 32 days at 20% relative humidity, and achieves a champion power conversion efficiency of 20.47%, while the pristine device gets an efficiency of 18.59% under the same condition. This work demonstrates a low-cost and efficient strategy to obtain high-performance and stable PSCs.
关键词： NH4F,carrier recombination,perovskite solar cells,interface modification
更新于2025-09-19 17:13:59
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22%‐efficient Cd‐free Cu(In,Ga)(S,Se) <sub/>2</sub> solar cell by all‐dry process using Zn <sub/>0.8</sub> Mg <sub/>0.2</sub> O and Zn <sub/>0.9</sub> Mg <sub/>0.1</sub> O:B as buffer and transparent conductive oxide layers
摘要： Cd‐free Cu(In,Ga)(S,Se)2 (CIGSSe)‐based solar cell fabricated by all‐dry process is developed to eliminate optical loss in CdS buffer and be readily applied into in‐line process. (Zn,Mg)O:B (BZMO) films can be deposited with the increased band‐gap energy (Eg) by metal organic chemical vapor deposition, and their optical and electrical properties are compared with those of (Zn,Mg)O:Al (AZMO) films prepared by sputtering method. It is shown that the AZMO and BZMO are suitable as transparent conductive oxide (TCO) layer to avoid the optical loss at short wavelength of the solar cell. The free‐carrier absorption of the BZMO films is additionally lower than that of the AZMO, attributable to the lower carrier concentration. The low resistivity of the BZMO films with Mg content up to 0.1 in a range of 3 × 10?2 to 6 × 10?2 Ω.cm is observed. The CIGSSe solar cells are then fabricated with the Cs‐treated CIGSSe layers as the absorbers. Consequently, the CIGSSe solar cell with the conventional CdS buffer layer possesses the conversion efficiency (η) of 21.7%. In addition, Cd‐free CIGSSe solar with a structure of glass/Mo/CIGSSe/Zn0.8Mg0.2O/Zn0.9Mg0.1O:B has the increased short‐circuit current density to 39.8 mA/cm2, thereby enhancing the η to 22.0%. This is because there is the reduced free‐carrier absorption and increased Eg (3.57 eV) of Zn0.9Mg0.1O:B layer, which is proved for the high‐level technology. The recombination rates of the solar cells are moreover discussed.
关键词： Zn1‐xMgxO:B,Cu(In,Ga)(S,Se)2,Cd‐free solar cell,recombination rates,Zn1‐xMgxO:Al
更新于2025-09-19 17:13:59
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Decoding Charge Recombination through Charge Generation in Organic Solar Cells
摘要： The in-depth understanding of charge carrier photogeneration and recombination mechanisms in organic solar cells is still an ongoing effort. In donor:acceptor (bulk) heterojunction organic solar cells, charge photogeneration and recombination are inter-related via the kinetics of charge transfer states—being singlet or triplet states. Although high-charge-photogeneration quantum yields are achieved in many donor:acceptor systems, only very few systems show significantly reduced bimolecular recombination relative to the rate of free carrier encounters, in low-mobility systems. This is a serious limitation for the industrialization of organic solar cells, in particular when aiming at thick active layers. Herein, a meta-analysis of the device performance of numerous bulk heterojunction organic solar cells is presented for which field-dependent photogeneration, charge carrier mobility, and fill factor are determined. Herein, a “spin-related factor” that is dependent on the ratio of back electron transfer of the triplet charge transfer (CT) states to the decay rate of the singlet CT states is introduced. It is shown that this factor links the recombination reduction factor to charge-generation efficiency. As a consequence, it is only in the systems with very efficient charge generation and very fast CT dissociation that free carrier recombination is strongly suppressed, regardless of the spin-related factor.
关键词： charge generation,spin-related factors,charge transfers,non-Langevin recombination
更新于2025-09-19 17:13:59
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Auger Recombination in Quantum Well Laser with Participation of Electrons in Waveguide Region
摘要： A new mechanism of nonradiative recombination of nonequilibrium carriers in semiconductor quantum wells is suggested and discussed. For a studied Auger recombination process the energy of localized electron-hole pair is transferred to barrier carriers due to Coulomb interaction. The analysis of the rate and the coefficient of this process is carried out. It is shown, that there exists two processes of thresholdless and quasithreshold types, and thresholdless one is dominant. The coefficient of studied process is a non-monotonous function of quantum well width having maximum in region of narrow quantum wells. Comparison of this process with CHCC process shows that these two processes of nonradiative recombination are competing in narrow quantum wells, but prevail at different quantum well widths.
关键词： waveguide region,Auger recombination,nonradiative recombination,quantum well laser,semiconductor
更新于2025-09-16 10:30:52
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Solvent engineering of LiTFSI towards high-efficiency planar perovskite solar cells
摘要： The performance and stability of perovskite solar cell (PSC) are inseparable from the quality of perovskite film, and the solvent engineering is being seemed as an effective strategy to enhance the properties of perovskite. Acetonitrile (ACN) is often used as a solvent to dissolve bis(trifluoromethane)sulfonimide lithium salt (LiTFSI), but ACN can corrode the perovskite film, which hinders the promotion of PSC efficiency and durability. Herein, a solvent engineering approach is implemented to search for suitable alternatives for ACN to abate the degradation of the perovskite films. The results demonstrate that isopropanol (IPA) with smaller polarity can effectively dissolve LiTFSI and slow down the degradation of the perovskite layer compared with ACN, which can result in the reduction of defects as well as the nonradiative recombination. Consequently, the devices using LiTFSI/IPA as additive achieve superior power conversion efficiencies (PCEs) with relatively less hysteresis effects and get a champion PCE of 19.43%, while the device using LiTFSI/ACN gets an inferior PCE of 17.12%.
关键词： Trap density,Nonradiative recombination,Solvent engineering,Isopropanol,Perovskite solar cells
更新于2025-09-16 10:30:52
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Investigation of Photophysical Properties of Ternary Zn–Ga–S Quantum Dots: Band Gap versus Sub-Band-Gap Excitations and Emissions
摘要： Highly luminescent ternary Zn?Ga?S quantum dots (QDs) were synthesized via a noninjection method by varying Zn/Ga ratios. X-ray diffraction and Raman investigations demonstrate composition-dependent changes with multiple phases including ZnGa2S4, ZnS, and Ga2S3 in all samples. Two distinct excitation pathways were identified from absorption and photoluminescence excitation spectra; among them, one is due to the band-gap transition appearing at around 375 and 395 nm, whereas another one observed nearby 505 nm originates from sub-band-gap defect states. Photoluminescence (PL) spectra of these QDs depict multiple emission noticeable at around 410, 435, 461, and 477 nm arising from crystallographic point defects formed within the band gap. The origin of these defects including zinc interstitials (IZn), zinc vacancies (VZn), sulfur interstitials (IS), sulfur vacancies (VS), and gallium vacancies (VGa) has been discussed in detail by proposing an energy-level diagram. Further, the time-dependent PL decay curve strongly suggests that the tail emission (appear around 477 nm) in these ternary QDs arises due to donor?acceptor pair recombination. This study enables us to understand the PL mechanism in new series of Zn?Ga?S ternary QDs and can be useful for the future utilization of these QDs in photovoltaic and display devices.
关键词： photophysical properties,ternary Zn?Ga?S quantum dots,sub-band-gap defect states,donor?acceptor pair recombination,photoluminescence,band-gap transition
更新于2025-09-16 10:30:52
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[IEEE 2019 8th International Symposium on Next Generation Electronics (ISNE) - Zhengzhou, China (2019.10.9-2019.10.10)] 2019 8th International Symposium on Next Generation Electronics (ISNE) - Structural optimization of 273nm deep ultraviolet laser in wave guide
摘要： The full width at half maxima (FWHM) of the LDs is very narrow, with small threshold current and high luminous power. Through simulation, it can be seen that the radiation recombination rate and wave intensity of different lateral positions of LDs are different. The waveguide layer of the high Al composition has a lower refractive index and can reduce the divergence angle of light. In this paper, the device structure is optimized by gradually increasing the Al component toward the p-cladding layer and decreasing the Al component toward p-side. Compared with the original structure, the grading wave guide proves that it can have better electrical characteristics and the FWHM is smaller.
关键词： grading wave guide,wave intensity,radiation recombination,FWHM
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Excitation and amplification of the unidirectionally propagating terahertz plasmon in a periodical graphene structure
摘要： The amplification of unidirectionally propagating plasmon modes excited by the incident terahertz wave in a periodical structure with an active graphene is studied theoretically. The amplification of propagating plasmon modes is due to radiative recombination in inverted graphene.
关键词： plasmon,radiative recombination,amplification,terahertz,graphene
更新于2025-09-16 10:30:52
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Ternary organic solar cells with NC70BA as a third component material exhibit high open-circuit voltage and small energy losses
摘要： The ternary organic solar cells (OSCs) were fabricated with PBDB-T as donor and a blend of IEICO-4F and NC70BA as the acceptor and the power conversion efficiency (PCE) reaches 10.92%. Due to good compatibility and cascade LUMO level among PBDB-T, a large amount of IEICO-4F and a small amount of NC70BA (the ratio of IEICO-4F:NC70BA is 85:15), which beneficial for adjusting lowest unoccupied molecular orbital (LUMO) levels of blend acceptor and wide energy offset between the donor and acceptor materials, leading to the enhancement of the open-circuit voltage (VOC). The optimized ternary PBDB-T:IEICO-4F:NC70BA films is more efficient exciton dissociation and suppress charge carrier recombination than that of binary PBDB-T:IEICO-4F and PBDB-T:NC70BA films, leading to small energy losses. In addition, this approach maintains PCE without sacrificing short-circuit current density (JSC) and fill factor (FF), even if the weak long and near-infrared wavelength photon harvesting. A more than 10% PCE improvement is achieve by employing a ternary strategy in comparison to PBDB-T:IEICO-4F-based binary OSCs with a PCE of 9.87%. Simultaneously, the optimized ternary PBDB-T:IEICO-4F:NC70BA OSCs exhibit the excellent thermal stability and 78.8% initial PCE under thermal annealing treatment at 80°C for 20 h.
关键词： Energy loss,Charge carrier recombination,Exciton dissociation
更新于2025-09-16 10:30:52