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[IEEE 2020 IEEE Latin America Electron Devices Conference (LAEDC) - San Jose, Costa Rica (2020.2.25-2020.2.28)] 2020 IEEE Latin America Electron Devices Conference (LAEDC) - Impact of the Hafnium Oxide as Hole Blocking Layer on the Performance of Organic Solar Cells
摘要： The effects of hafnium oxide (HfO2) as hole blocking layer (HBL) on the stability and degradation under air environment of inverted bulk heterojunction organic solar cells (iOSC), using as donor material thieno[3,4b]thiophene-alt-benzodithiophene (PTB7) and as acceptor material [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) are presented. The ultrathin films of HfO2 layers 0.9 nm of thick were deposited by thermal evaporation. The highest power conversion efficiency obtained (PCE) was of 8.33%. The current density-voltage characteristic (J-V) was modeled through the ideal-diode equivalent circuit model. For comparison, cells with poly [(9,9-bis (30- (N,N-dimethylamino) propyl) -2,7-fluorene) -alt-2,7- (9,9-dioctylfluorene)] (PFN) and Zinc Oxide (ZnO) as hole blocking layer were fabricated. The three groups of cells were exposed to air for 1000 h. The electrical parameters extracted from the current density–voltage characteristic (J–V) were analyzed. The PCE for cells manufactured with HfO2 as HBL remains around 30% after 1000 h under air environment, showing less degradation than iOSCs with ZnO.
关键词： electron transport layer,HfO2,PFN,PTB7:PC70BM solar cells,hafnium oxide,organic solar cells,ZnO,Degradation,OSC stability
更新于2025-09-23 15:19:57
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In situ Measuring Film-Depth-Dependent Light Absorption Spectra for Organic Photovoltaics
摘要： Organic donor–acceptor bulk heterojunction are attracting wide interests for solar cell applications due to solution processability, mechanical ?exibility, and low cost. The photovoltaic performance of such thin ?lm is strongly dependent on vertical phase separation of each component. Although ?lm-depth-dependent light absorption spectra measured by non-in situ methods have been used to investigate the ?lm-depth pro?ling of organic semiconducting thin ?lms, the in situ measurement is still not well-resolved. In this work, we propose an in situ measurement method in combination with a self-developed in situ instrument, which integrates a capacitive coupled plasma generator, a light source, and a spectrometer. This in situ method and instrument are easily accessible and easily equipped in laboratories of the organic electronics, which could be used to conveniently investigate the ?lm-depth-dependent optical and electronic properties.
关键词： light absorption,bulk heterojunction,spectroscopy,organic solar cells,depth pro?ling,organic photovoltaics
更新于2025-09-23 15:19:57
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Water-Processed Organic Solar Cells with Open-Circuit Voltages Exceeding 1.3V
摘要： Conjugated polyelectrolytes are commonly employed as interlayers to modify organic solar cell (OSC) electrode work functions but their use as an electron donor in water-processed OSC active layers has barely been investigated. Here, we demonstrate that poly[3-(6’-N,N,N-trimethyl ammonium)-hexylthiophene] bromide (P3HTN) can be employed as an electron donor combined with a water-soluble fullerene (PEG-C60) into eco-friendly active layers deposited from aqueous solutions. Spin-coating a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) layer prior to the P3HTN:PEG-C60 active layer deposition considerably increases the open-circuit voltage (Voc) of the OSCs to values above 1.3 V. Along with this enhanced Voc, the OSCs fabricated with the PEDOT:PSS interlayers exhibit 10-fold and 5-fold increases in short-circuit current density (Jsc) with respect to those employing bare indium tin oxide (ITO) and molybdenum trioxide coated ITO anodes, respectively. These findings suggest that the enhanced Jsc and Voc in the water-processed OSCs using the PEDOT:PSS interlayer cannot be solely ascribed to a better hole collection but rather to ion exchanges taking place between PEDOT:PSS and P3HTN. We investigate the optoelectronic properties of the newly formed polyelectrolytes using absorption and photoelectron spectroscopy combined with hole transport measurements to elucidate the enhanced photovoltaic parameters obtained in the OSCs prepared with PEDOT:PSS and P3HTN.
关键词： frontier orbitals,organic semiconductors,organic solar cells,conjugated polyelectrolytes,sustainable fabrication
更新于2025-09-23 15:19:57
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Organic Photovoltaics: Relating Chemical Structure, Local Morphology, and Electronic Properties
摘要： Substantial enhancements in the efficiencies of bulk-heterojunction (BHJ) organic solar cells (OSCs) have come from largely trial-and-error-based optimizations of the morphology of the active layers. Further improvements, however, require a detailed understanding of the relationships among chemical structure, morphology, electronic properties, and device performance. On the experimental side, characterization of the local (i.e., nanoscale) morphology remains challenging, which has called for the development of robust computational methodologies that can reliably address those aspects. In this review, we describe how a methodology that combines all-atom molecular dynamics (AA-MD) simulations with density functional theory (DFT) calculations allows the establishment of chemical structure–local morphology–electronic properties relationships. We also provide a brief overview of coarse-graining methods in an effort to bridge local to global (i.e., mesoscale to microscale) morphology. Finally, we give a few examples of machine learning (ML) applications that can assist in the discovery of these relationships.
关键词： Machine Learning,Density Functional Theory,Organic Photovoltaics,Organic Solar Cells,Bulk-Heterojunction,Electronic Properties,Coarse-Graining Methods,Local Morphology,Chemical Structure,All-Atom Molecular Dynamics
更新于2025-09-23 15:19:57
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Higha??Performance Ternary Organic Solar Cells with Morphologya??Modulated Hole Transfer and Improved Ultraviolet Photostability
摘要： Ternary bulk-heterojunction (BHJ) strategy synergistically combining the merits of fullerene and non-fullerene acceptors has been regarded as a promising approach to enhance the power conversion efficiencies (PCEs) of organic solar cells (OSCs). Herein, the fullerene derivative ICBA as the morphology regulator is incorporated into non-fullerene based PBDB-T-2F:BTP-4Cl (PM6:BTP-4Cl) system to fabricate the high-performance ternary OSCs. The amorphous ICBA prefers to homogeneously distribute in the BTP-4Cl phase to form the well-mixed acceptor domains due to their better miscibility, which distinctly reduces the exciton decay loss driven by the unfavorable phase separation and enhances BHJ morphology stability of ternary blends. The appropriate addition of ICBA induces the efficient long-range F?rster resonance energy transfer to BTP-4Cl and facilitates the ultrafast hole transfer process from BTP-4Cl to PM6, thereby contributing to charge carrier generation in the actual devices. Ultimately, the optimal ternary OSCs not only yield the average PCE higher than 16.5% but also show the superior ultraviolet photostability relative to binary control devices owing to the increased harvesting of ultraviolet photons, boosted charge transfer, more balanced charge transport and more stable nano-structural morphology. Our results provide the new insights to enable the simultaneously improved device performance and tolerance to UV light in highly efficient ternary OSCs.
关键词： hole transfer,non-fullerene,ultraviolet photostability,ternary organic solar cells
更新于2025-09-23 15:19:57
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Design of novel thiazolothiazole-containing conjugated polymers for organic solar cells and modules
摘要： One of the major challenges in the field of organic photovoltaics is associated with high-throughput manufacturing of efficient and stable organic solar cells. Practical realization of technologies for production of large-area organic solar cells requires the development of novel materials with a defined combination of properties ensuring sufficient reliability and scalability of the process in addition to good efficiency and operation stability of the devices. In this work, we designed two novel polymers comprising thiazolothiazole units and investigated their performance as absorber materials for organic solar cells and modules. Optimized small-area solar cells based on P1/[70]PCBM ([6,6]-phenyl-C71-butyric acid methyl ester) blends exhibited promising power conversion efficiency (PCE) of 7.5%, while larger area modules fabricated using slot die coating showed encouraging PCE of 4.2%. Additionally, the fabricated devices showed promising outdoor stability maintaining 60–70% of the initial efficiency after 20 sun days being exposed to natural sunlight at the Negev desert. The obtained results feature the designed polymer P1 as a promising absorber material for a large-scale production of organic solar cells under ambient conditions.
关键词： Thiazolothiazole,Conjugated polymers,Photovoltaic modules,Organic solar cells,Slot-die coating
更新于2025-09-23 15:19:57
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Efficient Organic Solar Cells Based on Non-Fullerene Acceptors with Two Planar Thiophene Fused Perylene Diimide Units
摘要： We designed and synthesized two non-fullerene acceptors (CDT-TFP and C8X-TFP), which comprise a central 4H-cyclopenta[2,1-b:3,4-b’]dithiophene (CDT) as the bridge and two thiophene-fused perylene diimide (TFP) units. The bulky side chains, such as the 4-hexylphenyl side chains, on the CDT bridge can effectively prevent the acceptor molecules from forming large aggregates and the π-π stacking of the terminal planar TFP units can form effective electron transport pathways when blending with the donor polymers. These non-fullerene acceptors are used to fabricate organic solar cells (OSCs) by blending with regioregular middle bandgap polymer reg-PThE. The as-cast devices based on reg-PThE:CDT-TFP show the best PCE of 8.36% with a Voc of 1.10 V, Jsc of 12.43 mA cm-2 and FF of 61.4%; whereas, the analogue PDI dimers (CDT-PDI) that comprising two PDI units bridged with a CDT unit, show only a 2.59% PCE with a Voc of 0.92 V, Jsc of 6.82 mA cm-2 and FF of 41.5%. Our results have demonstrated that non-fullerene acceptors comprising planar PDI units can achieve excellent photovoltaic performance and provide meaningful guidelines for the design of PDI based non-fullerene electron acceptors for efficient OSCs.
关键词： regioregular donor polymer,perylene diimide,organic solar cells,non-fullerene electron acceptors,planar
更新于2025-09-23 15:19:57
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Geminate recombination in organic photovoltaic blend PCDTBT/PC <sub/>71</sub> BM studied by out-of-phase electron spin echo spectroscopy
摘要： The key process in organic solar cell operation is charge separation under light illumination. Due to the low dielectric constant of organic materials, the Coulomb attraction energy within the interfacial charge-transfer state (CTS) is larger than the thermal energy. Understanding the mechanism of charge separation at the organic donor/acceptor interface still remains a challenge and requires knowledge of the CTS temporal evolution. To address this problem, the CTS in the benchmark photovoltaic blend PCDTBT/PC71BM was studied by the out-of-phase Electron Spin Echo (ESE). The protocol for determining the CTS geminate recombination rate for certain electron-hole distances was developed. Simulating the out-of-phase ESE trace for the CTS in the PCDTBT/PC71BM blend allows precise determination of the electron-hole distance distribution function and its evolution with the increase in the delay after the laser flash. Distances of charge separation up to 6 nm were detected upon thermalization at a temperature of 20 K. Assuming the exponential decay of the recombination rate, the attenuation factor β = 0.08 ??1 is estimated for the PCDTBT/PC71BM blend. Such a low attenuation factor is probably caused by a high degree of hole delocalization along the PCDTBT chain.
关键词： PCDTBT/PC71BM blend,electron spin echo,geminate recombination,organic solar cells,charge transfer state
更新于2025-09-23 15:19:57
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Impact of electrona??phonon coupling on the quantum yield of photovoltaic devices
摘要： In describing the charge carriers’ separation mechanism in the organic solar cell, providing a method, which considers the impact of all parameters of interest on the same footing within an inexpensive numerical effort, could play an essential role. We use here a simple tight-binding model to describe the dissociation of the charge carriers and investigate their dependence on the physical parameters of the system. We demonstrate that the quantum yield of the cell is subtly controlled by the collective action of the Coulomb interaction of the electron–hole pair, electron–phonon coupling, and the geminate recombination of the charge carriers. This approach should help us understand the performance of organic solar cells and optimize their efficiency.
关键词： electron–phonon coupling,quantum yield,organic solar cells,charge separation,photovoltaic devices
更新于2025-09-23 15:19:57
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Realizing the ultimate goal of fully solution-processed organic solar cells: a compatible self-sintering method to achieve silver back electrode
摘要： It is commonly believed that the ultimate goal of high throughput production of organic solar cells (OSCs) is the fully solution process in the fabrication. While it is highly desirable to form metal back electrodes to complete OSCs by solution process instead of high-vacuum evaporation to realize the goal, the complex solvents used in typical metal precursor solution and the post-treatment required such as high-temperature annealing will easily damage active layers and degrade OSC performances. The power conversion efficiency (PCE) for evaporation-free OSCs have only achieved 8%. Besides, there are limited studies that provide clear evidence to successfully eliminate the solvent issue brought by the directly solution-processed metal back electrode. In this work, we demonstrate a compatible self-sintering approach to connect silver nanoparticles into high-quality back electrode. The as-achieved film exhibits continuous crystal lattice, high purity, excellent conductivity and smooth morphology. Interestingly, since the self-sintering back electrode process is finished in short time and uses chemically compatible solvent, it will not degrade the organic active layer and favor high throughput OSCs fabrication. With the back electrode, the fully solution-processed OSCs achieve a PCE of 9.73% which is the highest reported PCE in evaporation-free OSCs to our best knowledge.
关键词： Solution process,minimum solvent issue,mild chemical sintering,organic solar cells,back electrode
更新于2025-09-23 15:19:57