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Synthesis and photovoltaic investigation of 8,10-bis (2-octyldodecyl) -8,10-dihydro-9H-bisthieno [2 ', 3': 7.8; 3``, 2 '': 5.6] naphtho [2,3-d] imidazol-9-one based conjugated polymers using non-fullerene acceptor
摘要： Two donor -acceptor (D-A) conjugated polymers designed on same 8,10-bis (2-octyldodecyl)-8,10-dihydro-9H-bisthieno [2`,3`:7,8; 3”,2”:5,6]naphtho [2,3-d]imidazole-9-one donor and dissimilar acceptor units, i.e. benzothiadiazole BT (P104) and fluorinated benzothiadiazole (P105) were synthesized and investigated their photophysical and electrochemical properties. The influence of the incorporation of fluorine atoms into the benzothiadiazole (BT) acceptor moiety in the polymer backbone on the photovoltaic performance when combined with the low bandgap non-fullerene acceptor ITIC-F was explored. The polymer solar cells based on P105:ITIC-F exhibited higher PCE (10.65 %) as compared to P104 :ITIC-F (8.32 %), resulted from the improved values of all the photovoltaic parameters. High value of Voc is linked with the deeper highest occupied molecular orbital energy level of P105 and the larger values of both short circuit current and fill factor are endorsed to the efficient exciton separation into charge carriers and their subsequent transfer owing to the increased value of dielectric constant and reduced value of exciton dissociation and energy loss and promoted balanced charge transportation. The intra/interchain interaction can be modulated by F atom substitution in the BT unit, resulting reduction in π-π stacking distance and increase in the crystal coherence length, benefiting the charge transportation in the active layer. These results offer a simple effective approach to regulate the optical and electrochemical properties and therefore increase the overall photovoltaic response.
关键词： D-A conjugated copolymer,non-fullerene acceptor,Polymer solar cells,morphology
更新于2025-09-12 10:27:22
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An A–D–D–A-type non-fullerene small-molecule acceptor with strong near-infrared absorption for high performance polymer solar cells
摘要： An acceptor–donor–donor–acceptor (A–D–D–A)-type near-infrared non-fullerene small-molecule acceptor IDT2-DFIC with indacenodithiophene–indacenodithiophene (IDT2) as a donating core and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (2FIC) as electron withdrawing end groups has been synthesized. Compared to A–D–A-type small-molecule acceptor IDIC-4F, IDT2-DFIC exhibits a low optical bandgap of 1.42 eV with strong absorption in the 450–874 nm region, and upshifted energy levels as an electron acceptor. Furthermore, the IDT2-DFIC-based devices exhibited higher and more balanced charge transport and smoother surface morphology. The power conversion efficiency (PCE) of the IDT2-DFIC-based devices is 10.06%, which is higher than that of the IDIC-4F-based devices (5.17%). Our work provides an efficient molecular design strategy to construct small molecule acceptors with near-infrared absorption.
关键词： IDT2-DFIC,near-infrared absorption,A–D–D–A-type,non-fullerene small-molecule acceptor,polymer solar cells
更新于2025-09-12 10:27:22
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Afterglow Effects as a Tool to Screen Emissive Non-Geminate Charge Recombination Processes in Organic Photovoltaic Composites
摘要： Disentangling temporally-overlapping charge carrier recombination events in organic bulk heterojunctions by optical spectroscopy is challenging. Here, a new methodology for employing delayed luminescence spectroscopy is presented. The proposed method is capable of distinguishing between recombination of spatially-separated charge carriers and trap-assisted charge recombination simply by monitoring the delayed luminescence (afterglow) of bulk heterojunctions with a quasi time-integrated detection scheme. Applied on the model composite of the donor poly(6,12-dihydro-6,6,12,12-tetraoctyl-indeno[1,2-b]fluorene-alt-benzothiadiazole) (PIF8BT) polymer and the acceptor ethyl-propyl perylene diimide (PDI) derivative, i.e. PIF8BT:PDI, the luminescence of charge-transfer (CT) states created by non-geminate charge recombination on the ns – μs time scale is observed. Fluence-dependent, quasi time-integrated detection of the CT luminescence monitors exclusively emissive charge recombination events, while rejecting the contribution of other early-time emissive processes. Trap-assisted and bimolecular charge recombination channels are identified based on their distinct dependence on fluence. The importance of the two recombination channels is correlated with the layer’s order and electrical properties of the corresponding devices. Four different microstructures of the PIF8BT:PDI composite obtained by thermal annealing are investigated. Thermal annealing of PIF8BT:PDI shrinks the PDI domains in parallel with the growth of the PIF8BT domains in the blend. Common to all states studied, the delayed CT luminescence signal is dominated by trap-assisted recombination. Yet, the minor fraction of fully-separated charge recombination in the overall CT emission increases as the difference in the size of the donor and acceptor domains in the PIF8BT:PDI blend becomes larger. Electric field-induced quenching measurements on complete PIF8BT:PDI devices confirm quantitatively the dominance of emissive trap-limited charge recombination and demonstrate that only 40% of the PIF8BT/PDI CT luminescence comes from the recombination of fully-separated charges, taking place within 200 ns after photoexcitation. The method is applicable to other non-fullerene acceptor blends beyond the system discussed here, if their CT state luminescence can be monitored.
关键词： multiple-diode equivalent circuit,fill factor,solar cell,charge trapping,perylene diimides,non-fullerene acceptors,delayed luminescence,photodetector
更新于2025-09-12 10:27:22
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Quinoidal Oligothiophenes Having Full Benzene Annelation: Synthesis, Properties, Structures, and Acceptor Application in Organic Photovoltaics
摘要： To achieve a complete closed-shell quinoidal state, bis(dicyanomethylene)-substituted quinoidal terthiophenes bearing benzene annelation at all thiophene rings were synthesized using a retro-Diels?Alder reaction as the key step. The unique structures and properties originating from the full benzene annelation were revealed by X-ray analysis as well as property measurements. Organic solar cells based on the combination of a donor polymer with a quinoidal terthiophene as an acceptor showed a power conversion e?ciency of 1.39%.
关键词： organic photovoltaics,retro-Diels?Alder reaction,non-fullerene acceptor,quinoidal oligothiophenes,benzene annelation
更新于2025-09-12 10:27:22
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A theoretical insight into multiple charge-transfer mechanisms at the P3HT/non-fullerenes interface in organic solar cells
摘要： Poly(3-hexylthiophene) (P3HT)-based organic solar cells (OSCs) have been developed in recent years because of easy-production, low-cost and large-area manufacture. However, fewer non-fullerene acceptors with higher power conversion efficiency (PCE) than PC61BM have been explored in P3HT-based OSCs. In this contribution, the excited states were in-depth analyzed towards probing the particularities of superior P3HT/non-fullerene systems. Multiple charge-transfer (CT) mechanisms involving intermolecular electric field (IEF), hot CT states and direct excitation of CT states were found, which suggests more favorable CT pathways exist in these P3HT/non-fullerene interfaces. Accordingly, the calculations on charge-transfer rates of all the investigated donor/acceptor interfaces further verified the positive effect of multiple CT pathways. In addition, the interesting hybrid Frenkel-CT states were firstly found to be relevant with the stronger electrostatic surface potential (ESP) differences on donor and acceptor for these P3HT/non-fullerene systems, which may provide a strategy for the design of high-efficiency OSCs.
关键词： non-fullerene,intermolecular electric field (IEF),P3HT,hybrid Frenkel-CT states,charge-transfer (CT) mechanisms,Organic solar cells (OSCs)
更新于2025-09-12 10:27:22
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Slot-die processing and encapsulation of non-fullerene based ITO-free organic solar cells and modules
摘要： Organic photovoltaic (OPV) devices have shown remarkable performance progress in recent years, reaching current record power conversion efficiency (PCE) values of 16.4% for single junction and 17.3% for multi junction devices, owing mostly to the impressive developments made within synthesis of new non-fullerene acceptors. This progress places organic solar cells at the forefront of thin-film photovoltaic technology. However, in order to meet industrial demands and reach high performance values in industrial settings, further research and development efforts within Roll-to-Roll (R2R) and Sheet-to-Sheet (S2S) processing of OPV devices under ambient conditions are required. Furthermore, OPV modules being manufactured through such up-scaled processing techniques should ideally be developed from low cost materials, and show good stability towards various different operational stress conditions. In this work, we demonstrate combined R2R and S2S development of ITO-free OPV devices, which are based on the non-fullerene material system PBDB-T:ITIC. The devices are processed from R2R vacuum sputtering and S2S slot-die coating at ambient conditions, and reach cell PCE values of 5.5%. In addition, we introduce a correlation between different barrier films, both commercial and sputtered inorganic coatings on ultra-clean PET, and the lifetime of the developed devices. The results therefore demonstrate an important step in the development of OPV devices from R2R and S2S processes in industrial settings.
关键词： organic solar cells and modules,Roll-to-Roll (R2R),Sheet-to-Sheet (S2S),organic photovoltaics (OPV),slot-die coating,device encapsulation,non-fullerene acceptors
更新于2025-09-12 10:27:22
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High Open‐Circuit Voltage Organic Photovoltaics Fabricated Using an Alkylidene Fluorene Derivative as a Non‐fullerene Acceptor
摘要： Alkylidene ?uorene-based molecular acceptors, AF-T-INCN and AF-T8-INCN, are synthesized for use in non-fullerene organic photovoltaics. Both AF-T-INCN and AF-T8-INCN exhibited absorption region from 400 to 700 nm in their neat ?lm states. Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels were found to be ?5.79/?3.80 eV for AF-T-INCN and ? 5.82/?3.79 eV for AT-T8-INCN, respectively. The organic solar cell devices fabricated with AF-T-INCN exhibited relatively low device performances with an open-circuit voltage (VOC) of 0.25 V, a short-circuit current density (JSC) 0.47 mA/cm2, a ?ll factor (FF) 29%, and power conversion ef?ciency (PCE) 0.03%, because of its strong aggregation in the blending condition. In contrast, AF-T8-INCN exhibited increased solubility and improved device performances with a high VOC of 1.24 V, a JSC 2.18 mA/cm2, a FF 28%, and PCE 0.76%.
关键词： Organic photovoltaic cells,Non-fullerene acceptor,Alkylidene ?uorene
更新于2025-09-12 10:27:22
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Potassium-Presenting Zinc Oxide Surfaces Induce Vertical Phase Separation in Fullerene-Free Organic Photovoltaics
摘要： Bulk heterojunction (BHJ) structure based organic photovoltaics (OPVs) have recently showed great potential for achieving high power conversion efficiencies (PCEs). An ideal BHJ structure would feature a large donor/acceptor interfacial area for efficient exciton dissociation and gradient distributions with high donor and acceptor concentrations near the anode and cathode, respectively, for efficient charge extraction. However, the random mixing of donor and acceptor in BHJ often suffers the severe charge recombination in the interface, resulting in poor charge extraction. Herein, we propose a new approach—treating the surface of the zinc oxide (ZnO) as electron transport layer with potassium hydroxide—to induce vertical phase separation of an active layer incorporating the non-fullerene acceptor IT-4F. Density functional theory calculations suggested that the binding energy difference between IT-4F and the PBDB-T-2Cl, to the potassium(K)-presenting ZnO interface is twice stronger than that for IT-4F and PBDB-T-2Cl to the untreated ZnO surface, such that it would induce more IT-4F moving toward the K-presenting ZnO interface than the untreated ZnO interface thermodynamically. Benefiting from efficient charge extraction, the best PCEs increased to 12.8% from 11.8% for PBDB-T-2Cl:IT-4F based devices, to 12.6% from 11.6% for PBDB-T-2Cl:Y1-4F based devices, to 13.5% from 12.2% for PBDB-T-2Cl:Y6 based devices, and to 15.7% from 15.1% for PM6:Y6 based devices.
关键词： DFT calculation,organic photovoltaics,potassium,vertical phase separation,non-fullerene acceptors
更新于2025-09-12 10:27:22
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Exploring chemical interaction between Diiodooctane and PEDOT-PSS electrode for metal electrode-free non-fullerene organic solar cells
摘要： Metal electrode-free organic solar cells with printable top electrode are attractive to realize the low cost of photovoltaics. Interaction between the printable electrode and active layer is critical to the device performance. In this work, we report on chemical interaction between printable polymer electrode poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and typically used additive of 1,8-Dioodooctane (DIO) in active layer. DIO can be converted to HI under the acidic condition of PEDOT:PSS, and the HI chemically reduces the PEDOT:PSS with the appearance of absorbance band at 800-1100 nm. The generation of I2 is verified by the color change of starch. The reaction results in decrease of its work function that hinders the efficient hole collection. A strategy is proposed to circumvent the detrimental interaction by inserting an ultrathin (15 nm) active layer without DIO between the initial active layer and PEDOT:PSS electrode. A power conversion efficiency (PCE) of 10.1% is achieved for the metal electrode-free non-fullerene organic solar cells.
关键词： PEDOT:PSS,1,8-Diiodooctane,chemical interaction,water transfer printing,organic solar cell,non-fullerene
更新于2025-09-12 10:27:22
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Designing dithienonaphthalene based acceptor materials with promising photovoltaic parameters for organic solar cells
摘要： Scientists are focusing on non-fullerene based acceptors due to their efficient photovoltaic properties. Here, we have designed four novel dithienonaphthalene based acceptors with better photovoltaic properties through structural modification of a well-known experimentally synthesized reference compound R. The newly designed molecules have a dithienonaphthalene core attached with different 2-(5,6-difluoro-2-methylene-3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (H1), 2-(5,6-dicyano-2-methylene-3-oxo-2,3-dihydroinden-1-ylidene)-malononitrile (H2), 2-(5-methylene-6-oxo-5,6-dihydrocylopenta[c]thiophe-4-ylidene)-malononitrile (H3) and 2-(3-(dicyanomethylene)-2,3-dihydroinden-1-yliden)malononitrile (H4) acceptor moieties (end-capped). The photovoltaic parameters of the designed molecules are discussed in comparison with those of the reference R. All newly designed molecules show a reduced HOMO–LUMO energy gap (2.17 eV to 2.28 eV), compared to the reference R (2.31 eV). Charger transfer from donor to acceptor is confirmed by a frontier molecular orbital (FMO) diagram. All studied molecules show extensive absorption in the visible region and absorption maxima are red-shifted compared to R. All investigated molecules have lower excitation energies which reveal high charge transfer rates, as compared to R. To evaluate the open circuit voltage, the designed acceptor molecules are blended with a well-known donor PBDB-T. The molecule H3 has the highest Voc value (1.88 V). TDM has been performed to show the behaviour of electronic excitation processes and electron hole location between the donor and acceptor unit. The binding energies of all molecules are lower than that of R. The lowest is calculated for H3 (0.24 eV) which reflects the highest charge transfer. The reorganization energy value for both the electrons and holes of H2 is lower than R which is indicative of the highest charge transfer rate.
关键词： absorption maxima,binding energies,reorganization energy,photovoltaic properties,open circuit voltage,charge transfer,dithienonaphthalene,HOMO–LUMO energy gap,non-fullerene based acceptors
更新于2025-09-12 10:27:22