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Trade‐Off between Exciton Dissociation and Carrier Recombination and Dielectric Properties in Y6‐Sensitized Nonfullerene Ternary Organic Solar Cells
摘要： Organic photovoltaics (OPVs) have emerged as a promising renewable energy generation technology in past decades. However, the deep understanding of the details in exciton dissociation and carrier recombination in ternary organic solar cells (OSCs) is still lacking. Herein, a novel ternary OSC based on a PTB7-Th:Y6:ITIC blend with a power conversion efficiency (PCE) enhancement of 29% is reported. A trade-off is surprisingly found to exist between the exciton dissociation and carrier recombination process. The addition of nonfullerene acceptor Y6 in the ternary blend is found to create an efficient exciton dissociation process but accelerates the free carrier recombination process. Dielectric properties are also studied for ternary OSCs. The addition of Y6 into the binary blend is found to tune down the dielectric constant of the active layer and as a result accelerates the carrier recombination. The best performance is obtained for PTB7-Th:Y6(5 wt%):ITIC(95 wt%)-based ternary devices. In addition to its balanced charge carrier mobility and efficient charge extraction process, PTB7-Th:Y6(5 wt%):ITIC(95 wt%)-based ternary devices reach a balance in the trade-off between the exciton dissociation and carrier recombination process and thus achieve the highest short-circuit current density (Jsc) value.
关键词： nonfullerene,carrier recombination and dielectric constants,ternary,organic solar cells,exciton dissociation
更新于2025-09-19 17:13:59
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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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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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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
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Efficient perovskite solar cells through suppressed non-radiative charge carrier recombination by processing additive
摘要： It was reported that non-radiative charge carrier recombination in hybrid perovskite materials restricted device performance of perovskite solar cells. In this study, we report efficient perovskite solar cells through suppressed non-radiative charge carrier recombination by processing additive, aminopropanoic acid. It is found that aminopropanoic acid not only modulate the crystal growth processes, but also minimize defects of CH3NH3PbI3 thin films. Moreover, the CH3NH3PbI3 thin films processed with addition of aminopropanoic acid exhibit both enhanced photoluminescence and electroluminescence, elongated charge carrier lifetime, indicating that non-radiative charge carrier recombination within CH3NH3PbI3 thin films is drastically suppressed. As a result, perovskite solar cells fabricated by CH3NH3PbI3 thin films processed with addition of aminopropanoic acid exhibit approximatively 15% enhanced efficiency as compared with that by pristine CH3NH3PbI3 thin film. All these results demonstrate that our finding provides a facial way to improve efficiency of perovskite solar cells.
关键词： open-circuit voltage loss,perovskite solar cells,photoluminescence,electroluminescence,non-radiative charge carrier recombination
更新于2025-09-16 10:30:52
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revealed by time-resolved photoluminescence spectroscopy
摘要： We systematically investigate the recombination mechanism of photogenerated charge carriers in bulk CsPbBr3 by means of time-resolved photoluminescence (TR-PL) spectroscopy at low temperature and various laser excitation powers. A dynamic recombination model is proposed to describe the TR-PL that predicts the time-dependent exciton and free-charge populations. It provides a clear representation of competing mono- and bimolecular recombination processes. A decrease in carrier lifetime with increasing laser intensity was observed that was attributed to exciton-exciton scattering. A bimolecular recombination coef?cient of ～10?7 cm3/s was obtained for exciton recombination. As the concentration of photoexcited carriers increases, stronger exciton-exciton annihilation occurs. The exciton-exciton annihilation rate for CsPbBr3 is 3.63 × 10?7 cm3 s?1 at 10-mW laser power. Notably, the exciton-exciton annihilation rate in bulk material is comparable to that obtained for photoexcited CsPbBr3 nanoscale quantum dots.
关键词： carrier recombination,bimolecular recombination,exciton-exciton annihilation,time-resolved photoluminescence,CsPbBr3
更新于2025-09-12 10:27:22
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Small energy loss and high open circuit voltage in conventional structure polymer solar cells with the mixture thin films of polyethylenimine ethoxylated and TiOX as the electron extraction layer and Ag as the cathode
摘要： One of the challenges facing the fabrication of high-performance conventional structure polymer solar cells (PSCs) is the development of new interface materials that have better air stability and charge carrier collection and transport ability. In this study, the mixture thin films of polyethylenimine ethoxylated (PEIE) and TiOX are developed as the electron extraction layer (EEL) and Ag as the cathode for the application in PSCs, replacing the Ca/Al composite cathode. Ultraviolet photoelectron spectroscopy (UPS) and space-charge-limited current (SCLC) measurements demonstrate that PEIE:TiOX/Ag shows appropriate energy levels, substantially reduced barrier potential, weakened charge carrier recombination and enhanced electron mobility. As a result, the PEIE:TiOX-based PSCs demonstrate not only an enhanced power conversion efficiency (PCE) of 10.94% but also the photovoltaic performance insensitive to the storage time, yielding an aged PCE that is 92% of the fresh PCE. This result can be further explained by the dependence of the charge carrier mobility on storage time. Our work suggests exploiting the PEIE:TiOX/Ag composite thin films as the composite cathode replacing Ca/Al thin films for successfully enhancing the photovoltaic performance and improving the stability of PSCs.
关键词： Energy losses,Barrier potential,Charge carrier recombination
更新于2025-09-12 10:27:22
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Monolayer HfTeSe4: A promising two-dimensional photovoltaic material for solar cells with high efficiency
摘要： Currently, atomically thin materials with high photovoltaic performance are urgently needed for applications in solar cells. Herein, by using first-principles calculations, we propose an excellent two-dimensional photovoltaic material, monolayer HfTeSe4, which can be exfoliated feasibly from its layered bulk. It behaves the semiconductor character with a moderate direct gap of 1.48 eV and exhibits remarkable absorbance coefficient of ~105 cm-1 in visible-light region. Meanwhile, monolayer HfTeSe4 shows ultrahigh photocurrent and a long carrier recombination life-time. And strain engineering can further modulate the recombination time of carriers. Moreover, the heterostructure between HfTeSe4 and Bi2WO6 is proposed as potential solar cells with the solar conversion efficiency up to ~20.8%. These extraordinary properties combined with its experimental feasibility makes monolayer HfTeSe4 particularly promising for photovoltaic device applications.
关键词： absorbance coefficient,solar conversion efficiency,carrier recombination,photovoltaic,first-principles calculations,photocurrent
更新于2025-09-12 10:27:22
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Solar Cell Simulations Made Easy
摘要： Numerical device simulations are a very powerful tool for the development of new types of highly efficient solar cells. The underlying theoretical framework describes many fundamental aspects of the complex flow of light through a photovoltaic device down to the atomic level, such that the most crucial simulation parameters can even be taken from first principles quantum mechanical simulations. But simpler approaches based on the Shockley diode equation are often sufficient to get an initial idea about the performance of a given basic material as part of a novel photovoltaic device. We discuss some of these simplified approaches and illustrate their applications, including the use of data from first principles simulations and/or experimental studies.
关键词： J-V curves,carrier extraction,photocurrent,solar cells,carrier recombination
更新于2025-09-11 14:15:04
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Aging Effect of a Cu(In,Ga)(S,Se) <sub/>2</sub> Absorber on the Photovoltaic Performance of Its Cd‐Free Solar Cell Fabricated by an All‐Dry Process: Its Carrier Recombination Analysis
摘要： Cd-free Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells are fabricated by an all-dry process (a Cd-free and all-dry process CIGSSe solar cell) with aged CIGSSe thin film absorbers. The aged CIGSSe thin films are kept in a desiccator cabinet under partial pressure of oxygen of ≈200 Pa for aging time up to 10 months. It is reported for the first time that aged CIGSSe thin film with increased aging time results in significant enhancement of photovoltaic performance of Cd-free and all-dry process CIGSSe solar cells, regardless of the alkali treatment. Based on carrier recombination analysis, carrier recombination rates at the interface and in the depletion region of the Cd-free and all-dry process CIGSSe solar cells are reduced owing to avoidance of sputtering damage on CIGSSe absorber surface, which is consistent with the strong electron beam-induced current signal near CIGSSe surface after the increased aging time. It is implied that the interface and near-surface qualities are clearly improved through the increased aging time, which is attributable to the self-forming of Inx(O,S)y near CIGSSe surface, which acts as a buffer layer. Ultimately, the 22.0%-efficient Cd-free CIGSSe solar cell fabricated by all-dry process is achieved with the aged Cs-treated CIGSSe absorber with the aging time of 10 months.
关键词： all-dry process,EBIC measurements,Cd-free Cu(In,Ga)(S,Se)2 solar cells,aging time,carrier recombination rate
更新于2025-09-11 14:15:04