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Building Intermixed Donor-Acceptor Architectures for Water-Processable Organic Photovoltaics
摘要： A modified synthesis method for aqueous nanoparticle printing inks, based upon vacuum-assisted solvent removal, is reported. Poly(3-hexylthiophene) : phenyl C61 butyric acid methyl ester nanoparticle inks were prepared via this modified miniemulsion method; leading to both an improvement in photoactive layer morphology and a substantial reduction in the ink fabrication time. A combination of UV-visible spectroscopy, photoluminescence spectroscopy and scanning transmission X-ray microscopy measurements revealed a nanoparticle morphology comprised of highly intermixed donor-acceptor domains. Consistent with these measurements, dynamic mechanical thermal analysis of the nanoparticles showed a glass transition temperature (Tg) of 104 °C, rather than a pure polymer phase or pure fullerene phase Tg. Together the spectroscopy, microscopy and thermomechanical data indicate that rapid solvent removal generates a more blended nanoparticle morphology. As such, this study highlights a new experimental lever for optimising nanostructure in the photoactive layer of nanoparticulate organic photovoltaic devices by enabling highly intermixed donor-acceptor architectures to be built from customised nanoparticulate inks.
关键词： organic photovoltaic,scanning transmission X-ray microscopy,morphology,colloidal inks,exciton dissociation,Nanostructure,eco-friendly processing
更新于2025-11-19 16:46:39
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Understanding the effect of solvent additive in polymeric thin film: turning a bilayer in a bulk heterojunction like photovoltaic device
摘要： Here we report the effect of an additive solvent, the 1,8-diiodooctane (DIO) on the performance of a bilayer organic photovoltaic (OPV) device which active layer comprises the poly[2,7-(9,9-bis(2 ethylhexyl)-dibenzosilole)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PSiF-DBT) as the electron donor material and C60 as the electron acceptor material. We observed that when the donor layer was treated with 1% of DIO the power conversion efficiency (PCE) of the device increase 138.4% in relation to the device with a non-treated donor layer and 21.3% in relation to the device containing a donor layer submitted to a thermal annealed. The main effects that lead to this increase in PCE are the large interfacial area between donor and acceptor materials and the improved conductivity at low voltages. The increase in polymer surface roughness leads to a more effective PSiF-DBT/C60 interface for exciton dissociation. This effect, as well as the increase in the conductivity, raised the short circuit current density (JSC) to 13.89 mA/cm2 and PCE to 4.84%. Our conclusions are supported by morphological analysis, chemical cross-sectional evaluations with advanced microscopy techniques, charge mobility measurements as well as by theoretical simulations of the devices in which the changes on the donor/acceptor interfacial area were considered. The outcomes suggest that, solvent additives could be an alternative treatment to replace the thermal annealing which imposes further difficulties to perform the lab-to-manufacturing upscaling.
关键词： solvent additive,PSiF-DBT,exciton dissociation,1,8-diiodooctane,C60,organic photovoltaic,power conversion efficiency
更新于2025-09-23 15:21:01
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Ultrafast Exciton Dissociation at the 2D-WS <sub/>2</sub> Monolayer/Perovskite Interface
摘要： In order for an excitonic photovoltaic (PV) device to perform efficiently, photogenerated excitons in the charge donor need to be dissociated through charge transfer (CT) to the acceptor rapidly after their photogeneration, and remain separated for a longer time to allow the collection of charges. To improve the efficiency of these steps, several combination of materials have been examined. Due to their excellent optical properties, two-dimensional transition metal dichalcogenides (2D-TMDs) have recently been explored. Another promising class of materials to platform efficient PVs is organic-inorganic perovskites. Here, we report on the ultrafast exciton dissociation through electron transfer from a 2D tungsten disulfide (WS2) monolayer to a thin layer of methylammonium lead iodide (CH3NH3PbI3) perovskites. Photoluminescence (PL) measurements showed that when the 2D-WS2 monolayer was covered with perovskites, its emission completely quenched, suggesting that the CT process is highly efficient. Despite that pump-probe spectroscopy measurements were carried out with a ~ 45 fs temporal resolution, the CT dynamics were not captured. A comparison of the ultrafast dynamics of the two band-edge excitons of the charge donor (2D-WS2) suggested that electron transfer is the dominant pathway of CT. Furthermore, these pump-probe measurements indicated that a small fraction of transferred electrons remained in the perovskites up to almost 2 ns. These findings may open a new horizon for understanding the dissociation of photogenerated excitons in 2D-TMD through hybridization with other class of nanomaterials.
关键词： Ultrafast Exciton Dissociation,Perovskite Interface,Hybrid Materials,Magnetic,Plasmonics,2D-WS2 Monolayer,Optical
更新于2025-09-23 15:21:01
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Efficient Exciton Dissociation Enabled by the End Group Modification in Non-Fullerene Acceptors
摘要： For organic photovoltaic (OPV) cells, in order to overcome the larger Coulombic binding energy between holes and electrons, an extra driving force is required for efficient exciton dissociation. Here, we report two non-fullerene acceptors named IO-4H and IO-4F for OPV cells. By employing the polymer PBDB-TF as a donor, PBDB-TF:IO-4H-based device only shows a power conversion efficiency (PCE) of 0.30% with a charge dissociation probability (Pdiss) of 13.3%. On the contrary, PBDB-TF:IO-4F-based device demonstrates a PCE of 7.85%, with a Pdiss of 81.3%. The photoelectric processes demonstrate that both devices have similar charge transport and charge recombination properties. The limitation of photovoltaic performance is the low exciton dissociation efficiency in the PBDB-TF:IO-4H-based device. The theoretical studies show the electrostatic potential (ESP) of IO-4H is negative in the end groups and similar to the ESP of PBDB-TF, while ESP of IO-4F is positive. PBDB-TF and the IO-4F may form a strong intermolecular electric field to assist the exciton dissociation. Our results suggest that increasing the ESP difference between donor and acceptor may be beneficial to promote exciton dissociation, thus improving photovoltaic performance.
关键词： organic photovoltaic,electrostatic potential,power conversion efficiency,exciton dissociation,non-fullerene acceptors
更新于2025-09-23 15:19:57
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Realizing high detectivity organic photodetectors in visible wavelength by doping highly ordered polymer PCPDTBT
摘要： A new method for realizing the response broadening of organic photodetectors (OPDs) using highly ordered polymer PCPDTBT doping has been proposed in this paper. The effects of PCPDTBT doping on the optical and electrical properties of OPDs were investigated experimentally. It was found that when the mass ratio of PTB7:PCPDTBT:PC61BM was 8.5:1.5:15, the response spectrum of the OPDs was broadened to 380–830 nm. The responsivity (R) and external quantum efficiency (EQE) of the OPDs reached 396, 244, 189 mA/W and 78%, 57%, 51% under 630, 530 and 460 nm illumination and (cid:0) 1 V bias, respectively, and the detectivity (D*) reached 1011 Jones. The results showed that the addition of PCPDTBT to PTB7:PC61BM increased the absorption of light at 700–830 nm. At the same time, the addition of PCPDTBT promotes the exciton dissociation interface in the active layer from the original one to the current three, they are PTB7:PCPDTBT, PTB7:PC61BM and PCPDTBT:PC61BM, which increase the probability of exciton dissociation in the active layer. In addition, the addition of highly ordered polymer PCPDTBT promotes the crystallization of the film and optimizes the carrier transport of the film. These synergistic effects promote the photocurrent of the OPDs.
关键词： Ternary bulk heterojunction,Exciton dissociation,Organic photodetectors,Microscopic morphology
更新于2025-09-23 15:19:57
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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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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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Extremely Efficient Photocurrent Generation in Carbon Nanotube Photodiodes Enabled by a Strong Axial Electric Field
摘要： Carbon nanotube (CNT) photodiodes have potential to convert light into electrical current with high efficiency. However, previous experiments have revealed photocurrent quantum yield (PCQY) well below 100%. In this work, we show that axial electric field increases the PCQY of CNT photodiodes. In optimal conditions our data suggest PCQY > 100%. We studied, both experimentally and theoretically, CNT photodiodes at room temperature using optical excitation corresponding to the S22, S33 and S44 exciton resonances. The axial electric field inside the pn junction was controlled using split gates that are capacitively coupled to the suspended CNT. Our results give new insight into the photocurrent generation pathways in CNTs, and the field dependence and diameter dependence of PCQY.
关键词： scanning photocurrent microscopy,carbon nanotube,carrier multiplication,exciton dissociation
更新于2025-09-16 10:30:52
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Hole Transfer Originating from Weakly Bound Exciton Dissociation in Acceptor–Donor–Acceptor Nonfullerene Organic Solar Cells
摘要： The underlying hole-transfer mechanism in high-efficiency OSC bulk heterojunctions based on acceptor?donor?acceptor (A?D?A) nonfullerene acceptors (NFAs) remains unclear. Herein, we study the hole-transfer process between copolymer donor J91 and five A?D?A NFAs with different highest occupied molecular orbital energy offsets (ΔEH) (0.05?0.42 eV) via ultrafast optical spectroscopies. Transient absorption spectra reveal a rapid hole-transfer rate with small ΔEH, suggesting that a large energy offset is not required to overcome the exciton binding energy. Capacitance?frequency spectra and time-resolved photoluminescence spectra confirm the delocalization of an A?D?A-structured acceptor exciton with weak binding energy. Relative to the hole-transfer rate, hole-transfer efficiency is the key factor affecting device performance. We propose that holes primarily stem from weakly bound acceptor exciton dissociation, revealing a new insight into the hole-transfer process in A?D?A NFA-based OSCs.
关键词： hole-transfer mechanism,organic solar cells,exciton dissociation,ultrafast optical spectroscopies,nonfullerene acceptors
更新于2025-09-12 10:27:22
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High detectivity organic photodetectors in the visible light wavelength with ternary bulk heterojunction
摘要： In this work, we report an ternary bulk heterojunction (t-BHJ) organic photodetectors (OPDs) based on P3HT, PTB7 and PC61BM. The effects of PTB7 added to P3HT:PC61BM on the optical and electrical properties of OPDs were investigated. It is found that when the mass ratio of P3HT:PTB7:PC61BM is 8:2:10, the response spectrum of the active layer is extended to 780 nm, The responsivity (R) and external quantum efficiency (EQE) of the OPDs are reached 178, 291, 241 mA/W and 35%, 68%, 65%, under 630, 530, and 460 nm illumination and ?1 V bias, respectively, and the detectivity (D*) reached 1012 Jones. The results show that the addition of PTB7 with appropriate mass ratio can increases the exciton generation and dissociation probability in P3HT:PC61BM, which increases the photocurrent of the device. In addition, the addition of PTB7 promotes the crystallization of the film, reduces the density of trap defects in the film, and reduces the dark current of the device.
关键词： Microscopic morphology,Organic photodetectors,Ternary bulk heterojunction,Exciton dissociation
更新于2025-09-12 10:27:22