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An Electrode Design Rule for Organic Photovoltaics Elucidated Using a Low Surface Area Electrode
摘要： It is widely considered that charge carrier extraction in bulk-heterojunction organic photovoltaics (BHJ OPVs) is most efficient when the area of contact between the semiconductor layers and the electrodes is maximized and the electrodes are electrically homogeneous. Herein, it is shown that ≈99% of the electrode surface can in fact be insulating without degrading the efficiency of charge carrier extraction, provided the spacing of the conducting areas is less than or equal to twice the optimal thickness of the BHJ layer. This striking result is demonstrated for BHJ OPVs with both conventional and inverted device architectures using two different types of BHJ OPVs, namely, PCDTBT:PC70BM and the ternary blend PBDB-T:ITIC-m:PC70BM. This finding opens the door to the use of a large pallet of materials for optical spacers and charge transport layers, based on a low density of conducting particles embedded in a wide bandgap insulating matrix.
关键词： nanoparticle electrode,organic photovoltaic,gold nanoparticle,transparent electrode,polymer solar cell,organic solar cell
更新于2025-09-11 14:15:04
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Intrinsically stable organic solar cells under high-intensity illumination
摘要： Organic photovoltaic cells are now approaching commercially viable efficiencies, particularly for applications that make use of their unique potential for flexibility and semitransparency1–3. However, their reliability remains a major concern, as even the most stable devices reported so far degrade within only a few years4–8. This has led to the belief that short operational lifetimes are an intrinsic disadvantage of devices that are fabricated using weakly bonded organic materials—an idea that persists despite the rapid growth and acceptance of organic light-emitting devices, which can achieve lifetimes of several million hours9. Here we study an extremely stable class of thermally evaporated single-junction organic photovoltaic cells. We accelerated the ageing process by exposing the packaged cells to white-light illumination intensities of up to 37 Suns. The cells maintained more than 87 per cent of their starting efficiency after exposure for more than 68 days. The degradation rate increases superlinearly with intensity, leading to an extrapolated intrinsic lifetime, T80, of more than 4.9 × 107 hours, where T80 is the time taken for the power conversion efficiency to decrease to 80 per cent of its initial value. This is equivalent to 27,000 years outdoors. Additionally, we subjected a second group of organic photovoltaic cells to 20 Suns of ultraviolet illumination (centred at 365 nanometres) for 848 hours, a dose that would take 1.7 × 104 hours (9.3 years) to accumulate outdoors. No efficiency loss was observed over the duration of the test. Overall, we find that organic solar cells packaged in an inert atmosphere can be extremely stable, which is promising for their future use as a practical energy-generation technology.
关键词： energy-generation technology,stability,organic photovoltaic cells,lifetime,high-intensity illumination
更新于2025-09-11 14:15:04
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1 cm <sup>2</sup> Organic Photovoltaic Cells for Indoor Application with over 20% Efficiency
摘要： Organic photovoltaic (OPV) technologies have the advantages of fabricating larger-area and light-weight solar panels on flexible substrates by low-cost roll-to-toll production. Recently, OPV cells have achieved many significant advances with power conversion efficiency (PCE) increasing rapidly. However, large-scale solar farms using OPV modules still face great challenges, such as device stability. Herein, the applications of OPV cells in indoor light environments are studied. Via optimizing the active layers to have a good match with the indoor light source, 1 cm2 OPV cells are fabricated and a top PCE of 22% under 1000 lux light-emitting diode (2700 K) illumination is demonstrated. In this work, the light intensities are measured carefully. Incorporated with the external quantum efficiency and photon flux spectrum, the integral current densities of the cells are calculated to confirm the reliability of the photovoltaic measurement. In addition, the devices show much better stability under continuous indoor light illumination. The results suggest that designing wide-bandgap active materials to meet the requirements for the indoor OPV cells has a great potential in achieving higher photovoltaic performance.
关键词： indoor application,power conversion efficiency,organic photovoltaic cells,photostability
更新于2025-09-11 14:15:04
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European Microscopy Congress 2016: Proceedings || Revealing phase separation and crystallinity in small molecule solar cells using 3D electron microscopy
摘要： Transmission Electron Microscopy (TEM) can be utilized to understand the morphology of organic bulk heterojunction (BHJ) solar cells and thus aid in improving device performance. We have previously shown that phase separation and formation of crystallinity is to be expected during co-evaporation of small molecule BHJ layers [1]. Using Electron Spectroscopic Imaging (ESI) [2] and electron diffraction, we found a significant influence of substrate and substrate temperature on the morphology of the photoactive layer during the fabrication of F4ZnPc:C60 BHJs. Whether or not the device is fabricated as inverted [3] or non-inverted cell influences crystal growth and, thus, phase separation during film formation. We have found that heating the substrate during BHJ film formation leads to an increase in efficiency for the inverted cell, whereas the non-inverted device shows no improvement. While the ESI measurements showed that substrate heating facilitates phase separation of the two materials, the difference in efficiency of the different device architectures could not be explained by this. Electron diffraction data indicated that crystallinity plays a role here. Since conventional ESI and electron diffraction only provide information about material distribution and crystallinity in a two-dimensional projection of the BHJ layers, high-resolution electron tomography was performed to gain insight into the three-dimensional structure. F4ZnPc:C60 was co-evaporated onto layers of neat F4ZnPc and C60, respectively. The measurements were performed under low-dose and LN2-cryo conditions in an FEI Titan Krios. This was necessary to preserve the sample, and foremost its crystallinity, since carbon-based materials, like C60, are prone to severe damage by electron irradiation. Figure 1 shows a bright-field TEM image of the BHJ on C60 (gold fiducials, seen in black, were used for tilt-series alignment). All images of the acquired tilt-series show crystalline areas such as the ones marked (A,B,C). The crystalline spacing seen here can be identified in the power spectra as characteristic for C60 (red: 0.85 nm, green: 0.5 nm and blue: 0.44 nm). As illustrated, such crystallinity can also be visualized in high-resolution electron tomograms, albeit only for smaller volumes at quite high magnification. To obtain a statistically significant distribution of crystallinity for different cell architecture and cell fabrication, larger volumes need to be analysed. For a given detector size, one needs to apply lower magnifications which results in lower resolution. However, the signature of pure crystals at these imaging conditions are a low variance in 3D, i.e. crystal distributions can easily be obtained from segmented 3D variance maps. A slice through the tomographic reconstruction of such samples can be seen in figure 2. Here, a BHJ film on C60 substrate is compared with a similar section through a tomogram of the BHJ on F4ZnPc. The gold fiducial indicates the top of the BHJ film. The homogeneous, aka crystalline areas are highlighted (red overlay). From the distribution of crystallinity we deduce, that large C60 crystals are found in both device architectures causing a very rough film surface. In the inverted device, these crystals can extend throughout the whole film, using the polycrystalline C60 substrate as seed for crystal growth, whereas the non-inverted BHJ showed C60 crystals starting somewhere in the middle of the film. Correlating this data with device performance, we find that C60 crystals which have grown throughout the BHJ layer are crucial for efficient devices.
关键词： Solar Cells,Crystallinity,Tomography,Organic Photovoltaic,CryoTEM
更新于2025-09-11 14:15:04
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Factors contributing to degradation of organic photovoltaic cells
摘要： The performance of organic photovoltaic (OPV) cells has considerably improved over the past decade, and now exceeds an energy conversion efficiency of 10%, the benchmark for practical use. One factor contributing to this increase is the development of π-conjugated linear acceptor molecules as alternatives to fullerene derivatives. Although conversion efficiency is an important issue for practical applications, device stability is also necessary for commercialization of OPV technologies. To date, long-term stability has been examined in OPV devices based on fullerenes. However, the factors involved in performance degradation remain poorly understood. It is difficult to address this problem because of the multilayer nature of the devices and many factors involved in degradation. In recent OPV devices based on π-conjugated molecules as acceptors, there have been few reports on stability under continuous light irradiation. Ensuring the stability of the π-conjugated molecules under illumination and electrical operation is critical for achieving practical use of OPV devices. In this paper, we comprehensively analyzed OPV devices based on EH-IDTBR as an acceptor material. We identified a decrease in OPV performance of approximately 50% under 100-hour light irradiation, which we attribute to increased resistance of the organic semiconductor layer. The increase in resistance was caused by a decrease in the number of carriers, suggesting that structural changes in the EH-IDTBR molecule are an important factor affecting degradation.
关键词： Durability,impedance measurement,organic photovoltaic,stability,MALDI-TOF-MS
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE International Conference on RFID Technology and Applications (RFID-TA) - Pisa, Italy (2019.9.25-2019.9.27)] 2019 IEEE International Conference on RFID Technology and Applications (RFID-TA) - Energy Harvesting Based On Printed Organic Photovoltaic Cells for RFID Applications
摘要： This work discusses the possibility of using printed organic photovoltaic cells in order to increase the performance of UHF RFID sensor tags. As a proof of concept, an organic photovoltaic (OPV) cell was used to power the chip SL900A that incorporates a sensor front-end interface capable of measuring voltages, currents, resistances, and capacitances. Several read range measurements were realized using other types of power sources and compared to OPV. Results based on the OPV cell showed a significant enhancement in the tag read range (up to 80%) under low light conditions which opens the door for several IoT applications.
关键词： IoT,Organic photovoltaic,Sensors,UHF RFID Tags,Energy Harvesting
更新于2025-09-11 14:15:04
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Highly Efficient Indoor Organic Solar Cells by Voltage Losses Minimization through Fine-tuning of Polymer Structures
摘要： Herein we report a detailed study on the optoelectronic properties, photovoltaic performance, structural conformation, morphology variation, charge carrier mobility and recombination dynamics in bulk heterojunction (BHJ) solar cells comprising of a series of donor-acceptor (D-A) conjugated polymers as electron donors based on benzodithiophene (BDT) and 5,8-bis(5-bromothiophen-2-yl)-6,7-difluoro-2,3-bis(3-(octyloxy)phenyl)quinoxaline as a function of the BDT’s thienyl substitution (alkyl (WF3), alkylthio (WF3S) and fluoro (WF3F)). It is manifested the synergistic positive effects of the fluorine substituents on the minimization of the bimolecular recombination losses, the reduction of the series resistances (RS), the increment of the shunt resistances (RSh), the suppression of the trap-assisted recombination losses, the balanced charge transport, the finer nanoscale morphology and the deeper highest occupied molecular orbital (EHOMO) versus the alkyl- and alkylthio- substituents. According to these findings, WF3F:[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) based-organic photovoltaic (OPV) device is a scarce example that feature a high power conversion efficiency (PCE) of 17.34% under 500 lx indoor LED light with a high open-circuit voltage (VOC) of 0.69 V, due to the suppression of the voltage losses and a PCE of 9.44% at 1-sun (100 mW/cm2) conditions, simultaneously.
关键词： Series and Shunt resistances,Coherence length,Conjugated polymers,Wide-angle X-ray scattering,Organic photovoltaic devices,Recombination losses,Indoor lighting conditions
更新于2025-09-11 14:15:04
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Processing Strategies for an Organic Photovoltaic Module with over 10% Efficiency
摘要： A large-area module (active area > 20 cm2) with a power conversion efficiency (PCE) of 10.4% (certified at 10.1%) using a non-fullerene blend was demonstrated, which is by far the highest PCE reported to date. The same module also delivers a power of ~40 mW/cm2 (PCE ~22%) under indoor lighting. Equally important, PCEs of 12%–14% were achieved for blends processed in ambient and/or without halogenated solvent.
关键词： module,halogen-free solvent,non-fullerene acceptor,ambient processing,organic photovoltaic,efficiency
更新于2025-09-11 14:15:04
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17% efficiency organic photovoltaic cell with superior processability
摘要： The development of organic photoactive materials, especially the new-emerging non-fullerene electron acceptors (NFAs), has enabled rapid progress in organic photovoltaic (OPV) cells in recent years. Although the power conversion efficiencies (PCEs) of the top-performance OPV cells have surpassed 16%, the devices are usually fabricated via a spin-coating method and are not suitable for large-area production. Here, we demonstrate that the fine-modification of the flexible side chains of NFAs can yield 17% PCE for OPV cells. More crucially, as the optimal NFA has a suitable solubility and thus a desirable morphology, the high efficiencies of spin-coated devices can be maintained when using the scalable blade-coating processing technology. Our results suggest that the optimization of the chemical structures of the OPV materials can improve the device performance. This has great significance in larger-area production technologies that provide important scientific insights for the commercialization of OPV cells.
关键词： non-fullerene acceptor,processability,power conversion efficiency,organic photovoltaic cells,scalable large-area production
更新于2025-09-11 14:15:04
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The Influence of Moisture on the Energy Level Alignment at the MoO <sub/>3</sub> /Organic Interfaces
摘要： MoO3 is widely used in polymer-based organic solar cells as an anode buffer layer due to its high workfunction and formation of a strong dipole at the MoO3/polymer interface facilitating the charge transfer across the MoO3/polymer interface. In the present work we show that exposure of the MoO3/polymer interface to moisture attracts water molecules to the interface via diffusion. Due to their own strong dipole water molecules counter the dipole at the MoO3/polymer interface. As a consequence, the charge transfer across the MoO3/polymer will reduce and affect the charge transport across the interface. The outcome of this work thus suggest that it is critical to keep the MoO3/polymer interface moisture free which requires special precautions in device fabrications. The composition of the MoO3/P3HT:PC61BM interface is analyzed with X-ray photoelectron spectroscopy and the depth profiling technique neutral impact collision ion scattering spectroscopy. The results show that the concentration of oxygen increases upon exposure but leave the oxidation state of the Mo unchanged. Valence electron spectroscopy technique shows that the dipole across the MoO3/P3HT:PC61BM interface decreases even for short time exposure to atmosphere due to the diffusion of water molecules to the interface. The far-ranging consequences for organic electronic devices are discussed.
关键词： exposure to air,interface,dipole formation,electron spectroscopy,metal oxide,organic photovoltaic,conjugated polymer
更新于2025-09-11 14:15:04