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Effects of fluorination and thermal annealing on charge recombination processes in polymer bulk-heterojunction solar cells
摘要： We investigate the effect of fluorination on the photovoltaic properties of an alternating conjugated polymer composed of 4,8-di-2-thienylbenzo[1,2-b:4,5-b0]dithiophene and 4,7-bis([2,20-bithiophen]-5-yl)-benzo-2-1-3-thiadiazole (4TBT) units in bulk-heterojunction solar cells. The unsubstituted and fluorinated polymers afford very similar open-circuit voltages and fill factor values, but the fluorinated polymer performed better due to enhanced aggregation which provides a higher photocurrent. The photovoltaic performance of both materials improved upon thermal annealing at 150–200 °C as a result of a significantly increased fill factor and open-circuit voltage, counteracted by a slight loss in photocurrent. Detailed studies of the morphology, light intensity dependence, external quantum efficiency and electroluminescence allowed the exploration of the effects of fluorination and thermal annealing on the charge recombination and the nature of the donor–acceptor interfacial charge transfer states in these films.
关键词： polymer bulk-heterojunction solar cells,thermal annealing,charge recombination,fluorination,photovoltaic properties
更新于2025-10-22 19:40:53
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Hole Blocking Layer-Free Perovskite Solar Cells with High Efficiencies and Stabilities by Integrating Subwavelength-Sized Plasmonic Alloy Nanoparticles
摘要： Perovskite solar cells hold great promise as prospective alternatives of renewable power sources. Recently hole blocking layer-free perovskite solar cells, getting rid of complex and high-temperature fabrication processes, have engaged in innovative designs of photovoltaic devices. However, the elimination of the hole blocking layer constrains the energy conversion efficiencies of perovskite solar cells, and severely degrades the stabilities. In this paper a simple approach (without energy-consuming and time-consuming procedures) for the fabrication of hole blocking layer-free perovskite solar cells has been demonstrated by an integration of copper-silver alloy nanoparticles, which are synthesized by wet chemical method with controllable diameters and elemental compositions. The rear-side integration of the subwavelength-sized silver-copper alloy particles (200 nm diameter), through a spraying/drying method, realizes a pronounced absorption enhancement of the perovskite layer by effectively light scattering in a broadband wavelength range, and achieves a series resistance decrease of the solar cell due to high electrical conductivities of the alloy particles. The particle integration achieves the highest efficiency of 18.89% due to the significant improvement in both optical and electrical properties of solar cells, making this device one of the highest-performing blocking layer-free perovskite solar cells and plasmonic perovskite solar cells. Moreover, the copper-based nanoparticles prevent the perovskite from diffusing into metal back electrodes. Because the diffusion can lead to a severe corrosion of the Au electrode and thus an efficiency degradation, the alloy nanoparticle integration between the perovskite and the electrode results in 80% and 200% improvements in the long-term stability and the photostability of solar cells, respectively. Through the proposed simple and effective fabrication process, our results open up new opportunities in the manufacturability of perovskite solar cells.
关键词： light scattering,Perovskite solar cells,plasmonic,subwavelength-sized,alloy,hole blocking layer,stability
更新于2025-10-22 19:40:53
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Infrared Light Management Using a Nanocrystalline Silicon Oxide Interlayer in Monolithic Perovskite/Silicon Heterojunction Tandem Solar Cells with Efficiency above 25%
摘要： Perovskite/silicon tandem solar cells are attractive for their potential for boosting cell efficiency beyond the crystalline silicon (Si) single-junction limit. However, the relatively large optical refractive index of Si, in comparison to that of transparent conducting oxides and perovskite absorber layers, results in significant reflection losses at the internal junction between the cells in monolithic (two-terminal) devices. Therefore, light management is crucial to improve photocurrent absorption in the Si bottom cell. Here it is shown that the infrared reflection losses in tandem cells processed on a flat silicon substrate can be significantly reduced by using an optical interlayer consisting of nanocrystalline silicon oxide. It is demonstrated that 110 nm thick interlayers with a refractive index of 2.6 (at 800 nm) result in 1.4 mA cm?2 current gain in the silicon bottom cell. Under AM1.5G irradiation, the champion 1 cm2 perovskite/silicon monolithic tandem cell exhibits a top cell + bottom cell total current density of 38.7 mA cm?2 and a certified stabilized power conversion efficiency of 25.2%.
关键词： monolithic perovskite/silicon tandem solar cells,infrared photocurrent absorption,nanocrystalline silicon oxide interlayers
更新于2025-10-22 19:40:53
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Effect of Thionation on the Performance of PNDIT2-Based Polymer Solar Cells
摘要： All-polymer solar cells have gained traction in recent years with solar cell performance of over 11% power conversion efficiency (PCE) recently demonstrated. The n-type polymer PNDIT2, also known as N2200 or P(NDI2OD-T2), has been extensively used for both photovoltaic as well as field-effect transistor applications. When paired with donor materials that have appropriately aligned energy-levels, PNDIT2 has exhibited device efficiencies over 10% PCE, and organic field effect transistors fabricated with PNDIT2 exhibit mobilities over 1 cm2/Vs. Thionation of the NDI moiety, which is the substitution of imide oxygen with sulfur atoms, has been shown to improve the field-effect transistor performance of NDI-based small molecules. Applying this strategy to PNDIT2, we explored the effect that thionation, in a 2S-trans configuration, has on the performance of all-polymer solar cells fabricated with the donor polymer PTB7-Th. Solar cells were fabricated with the original polymer, PNDIT2, as a reference, and an optimized efficiency of 4.85% was achieved. As samples with 100% conversion to 2S-trans configuration could not be produced due to synthetic limitations, batches with increasing ratios of 1S to 2S-trans thionation (15:85, 7:93, and 5:95) were studied. Devices with thionated PNDIT2 exhibited a systematic lowering of photovoltaic parameters with increasing thionation, resulting in device efficiencies of just 0.84%, 0.62%, and 0.42% PCE. The lower performance of the thionated blends is attributed to poor π-π stacking order in the thionated PNDIT2 phase, resulting in lower electron mobilities and finer phase separation. Evidence in support of this conclusion is provided by grazing incidence wide-angle X-ray scattering, transmission electron microscopy, photoluminescence quenching, transient photocurrent analysis, and SCLC measurements.
关键词： π-π stacking,PNDIT2,Thionation,All-polymer solar cells,Power conversion efficiency
更新于2025-10-22 19:40:53
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New copolymer involving PVK and F8BT for organic solar cells applications: Design, synthesis, characterization and theoretical studies
摘要： The new PVK-F8BT copolymer coupled to poly (9-vinylcarbazole) and poly(9,9-dioctyl?uorene-alt-benzothiadiazole) has been designed and elaborated by chemical oxidation for organic solar cells applications. Structural and photophysical properties were examined using di?erent and complementary techniques (Infrared, optical absorption, stationary and time resolved photoluminescence). The PVK-F8BT exhibited a broad absorption band covering the wavelength range from 200 nm to 700 nm covering the solar spectrum and, highlighting the charge transfer process. Moreover, the PVK-F8BT, showed a low band gap to be found to 1.9 eV and it average lifetime (2.62 ns) are longer than that of F8BT. The resulting copolymer exhibits original optical properties compared to the PVK and F8BT ones. The experimental analyses were coupled to theoretical calculations based on density functional theory and time-dependant density functional theory methods in order to better understand the structure-properties correlation. Furthermore DFT and TD-DFT calculations of the PVK-F8BT have been exploited to optimize the copolymer-based composites based on bulk heterojunction based organic photovoltaic copolymers with the 1-(3-methoxycarbonyl) propyl-1-phenyl-[6,6]–C61, as an acceptor. Thus, the band gap decreased to 1.69 eV, the power energy conversion e?ciency was about 7%. Our results have allowed us to discover a promising new photovoltaic material.
关键词： TD-DFT,Optical properties,Solar cells,Donor-acceptor,Charge transfer
更新于2025-10-22 19:40:53
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Surface Plasmon Resonance Enhancement of PbS Quantum Dot-Sensitized Solar Cells
摘要： Lead sulfide (PbS)-sensitized quantum dot solar cells (QDSC) were fabricated using TiO2 and TiO2–Au plasmonic nanocomposite films by successive ionic layer adsorption and reaction (SILAR) method. The average size of gold nanoparticles (GNPs) used for fabricating nanocomposite films was ~ 15 nm. Thin plasmonic QDSC, with a film thickness of 10 μm, showed an increase of ~ 11% in photocurrent and ~ 6% in overall energy conversion efficiency compared to the device without GNPs. The improved performance of QDSCs is attributed to the increased absorption due to the plasmonic near-field effects of the incorporated GNPs. High-efficiency PbS/CdS-co-sensitized thick cells with 16 μm bilayer TiO2 also showed improvement in photocurrent and efficiency. The results show that the plasmonic-enhanced absorption can be used to augment efficiency of QDSC devices in much the same fashion as that of dye-sensitized solar cells.
关键词： Gold nanoparticles,Quantum dot-sensitized solar cells,Plasmonics,Photovoltaics
更新于2025-10-22 19:40:53
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Achieving a high open-circuit voltage in inverted wide-bandgap perovskite solar cells with a graded perovskite homojunction
摘要： Wide-bandgap (~1.7-1.8 eV) perovskite solar cells have attracted substantial research interest in recent years due to their great potential to fabricate efficient tandem solar cells via combining with a lower bandgap (1.1-1.3 eV) absorber (e.g., Si, copper indium gallium diselenide, or low-bandgap perovskite). However, wide-bandgap perovskite solar cells usually suffer from large open circuit voltage (Voc) deficits caused by small grain sizes and photoinduced phase segregation. Here, we demonstrate that in addition to large grain sizes and passivated grain boundaries, controlling interface properties is critical for achieving high Voc’s in the inverted wide-bandgap perovskite solar cells. We adopt guanidinium bromide solution to tune the effective doping and electronic properties of the surface layer of perovskite thin films, leading to the formation of a graded perovskite homojunction. The enhanced electric field at the perovskite homojunction is revealed by Kelvin probe force microscopy measurements. This advance enables an increase in the Voc of the inverted perovskite solar cells from an initial 1.12 V to 1.24 V. With the optimization of the device fabrication process, the champion inverted wide-bandgap cell delivers a power conversion efficiency of 18.19% and sustains more than 72% of its initial efficiency after continuous illumination for 70 h without encapsulation. Additionally, a semitransparent device with an indium tin oxide back contact retains more than 88% of its initial efficiency after 100 h maximum power point tracking.
关键词： wide-bandgap perovskite solar cells,perovskite homojunction,guanidinium bromide
更新于2025-10-22 19:40:53
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AIP Conference Proceedings [Author(s) THE 3RD INTERNATIONAL CONFERENCE ON OPTOELECTRONIC AND NANO MATERIALS FOR ADVANCED TECHNOLOGY (icONMAT 2019) - Kerala, India (3–5 January 2019)] - Effect of substrate temperature on spray coated PEDOT:PSS thin film morphology for organic solar cell
摘要： The effect of substrate temperature on the spray coated poly (3,4-ethylenedioxythiophene): poly (styrenesulfonic acid) (PEDOT: PSS) hole transport layer (HTL) is explored in terms of morphological, electrical and photovoltaic characterization. The substrate temperature is varied in three steps 100, 150 and 200°C during the spray deposition of PEDOT: PSS thin film layer. Scanning electron microscopy (SEM) and optical microscopy images reveal that for the substrate temperatures of 100°C and 150°C, the morphology of PEDOT: PSS layer is improved and further increasing the temperature to 200°C, voids and cracks are formed in the films. These voids and cracks influence the conductivity of PEDOT: PSS layer which reduces from 4.7 for 150°C to 3.9 S/cm for 200°C. Organic solar cells (OSCs) using PTB7:PC71BM absorber layer on the spray coated PEDOT:PSS HTL show an efficiency increase from 2.34 for 100°C to 2.88% for 150°C and then decrease to 1.88% for 200°C.
关键词： substrate temperature,spray coating,PEDOT:PSS,morphology,organic solar cells
更新于2025-10-22 19:40:53
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Light management in crystalline silicon thin-film solar cells with imprint-textured glass superstrate
摘要： The implementation of light management textures in thin-film solar cells often simultaneously causes an undesired deterioration of electronic performance. Here, we introduce a simple yet effective technique for improved light management in liquid phase crystallized silicon thin-film solar cells on glass. By imprinting pyramidal textures on the sun-facing side of the glass superstrate, absorber and functional layers of the device remain unaffected while light in-coupling is significantly increased. An increase of short-circuit current density by 2.5 mA cm2 was observed by texturing the glass in this way, corresponding to an enhanced power conversion efficiency from 12.9% to 13.8%. Optical simulations allow to attribute the increase in equal shares to an anti-reflective effect at the air-glass interface as well as light scattering and multiple passes through the glass. The technology allows for independent optimization of optical performance without compromising on electronic material issues and is therefore useable for any other solar cell technology using a glass superstrate.
关键词： Light management,Nano-imprint lithography,Liquid phase crystallization,Thin-film solar cells,Silicon
更新于2025-10-22 19:40:53
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Facile enhancement of bulk heterojunction solar cells performance by utilizing PbSe nanorods decorated with graphene
摘要： An efficient approach for improving the photoelectrical conversion efficiency (PCE) of the bulk heterojunction (BHJ) solar cells, based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acidmethyl ester (PC61BM), by the incorporating PbSe nanorods decorated with graphene (G) into their active layer has been reported for the first time. Pristine PbSe and PbSe:G composites (with different amount of graphene) are synthesized via hydrothermal process and the formation mechanism is explained. The systematic investigation indicates that the crystallite size of PbSe:G increases with increasing graphene content. The PCE of the classical BHJ solar cells based on P3HT:PC61BM is improved from 2.32 up to 2.57 % by the incorporation of pristine PbSe. It is also enhanced by the incorporation of PbSe:G up to certain composition of graphene in which a maximum PCE value of 5.16 % is achieved. The external quantum efficiency of the BHJ solar cells is also investigated. The photovoltaic parameters are discussed based on the morphology variation detected by scanning electron microscope and atomic force microscope of the active layer together with their UV-VIS absorption measurements.
关键词： Graphene,optical absorption,PbSe nanorods,surface morphology,BHJ solar cells
更新于2025-10-22 19:40:53