Effect of the Molecular Weight of Poly(3-hexylthiophene) on the Morphology and Performance of Polymer Bulk Heterojunction Solar Cells (original) (raw)
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Solar Energy Materials and Solar Cells, 2006
The performance of organic solar cells based on the blend of regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) is strongly influenced by blend composition and thermal annealing conditions. X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) diffraction measurements show that in the considered blends, ordering of P3HT plays a key role in understanding the PV-performance. It is demonstrated that the natural tendency of regioregular P3HT to crystallize is disturbed by the addition of PCBM. Annealing however improves the crystallinity, explaining the observed spectral broadening and is also resulting in a higher mobility of the holes in P3HT. r
Effect of polydispersity on the bulk-heterojunction morphology of P3HT:PCBM solar cells
Journal of Polymer Science Part B: Polymer Physics
Bulk heterojunctions (BHJ) based on semiconducting electron-donor polymer and electronacceptor fullerene have been extensively investigated as potential photoactive layers for organic solar cells (OSCs). In the experimental studies, poly-(3-hexyl-thiophene) (P3HT) polymers are hardly monodisperse as the synthesis of highly monodisperse polymer mixture is a near impossible task to achieve. However, the majority of the computational efforts on poly-(3-hexylthiophene): phenyl-C61-butyric acid methyl ester (P3HT:PCBM) based OSCs, a monodisperse P3HT is usually considered. Here, results from coarse-grained molecular dynamics (CGMD) simulations of solvent evaporation and thermal annealing process of the BHJ are shared describing the effect of variability in molecular weight (a.k.a. polydispersity) on the morphology of the active layer. Results affirm that polydispersity is beneficial for charge separation as the interfacial area is observed to increase with higher dispersity. Calculations of percolation and orientation tensors, on the other hand, reveal that a certain polydispersity index (PDI) ranging between 1.05-1.10 should be maintained for optimal charge transport. Most importantly, these results point out that the consideration of polydispersity should be considered in computational studies of polymer based organic solar cells.
P3HT/PCBM bulk heterojunction organic photovoltaics: Correlating efficiency and morphology
Nano letters, 2011
Controlling thin film morphology is key in optimizing the efficiency of polymer-based photovoltaic (PV) devices. We show that morphology and interfacial behavior of the multicomponent active layers confined between electrodes are strongly influenced by the preparation conditions. Here, we provide detailed descriptions of the morphologies and interfacial behavior in thin film mixtures of regioregular poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM), a typical active layer in a polymer-based PV device, in contact with an anode layer of PEDOT-PSS and either unconfined or confined by an Al cathode during thermal treatment. Small angle neutron scattering and electron microscopy show that a nanoscopic, bicontinuous morphology develops within seconds of annealing at 150°C and coarsens slightly with further annealing. P3HT and PCBM are shown to be highly miscible, to exhibit a rapid, unusual interdiffusion, and to display a preferential segregation of one component to the electrode interfaces. The ultimate morphology is related to device efficiency.
Journal of Applied Physics, 2005
Regioregular poly͑3-hexylthiophene͒ ͑RR-P3HT͒ is a promising candidate for polymer photovoltaic research due to its stability and absorption in the red region. In this manuscript, we report polymer photovoltaic devices based on RR-P3HT:methanofullerene ͓6,6͔-phenyl-C 61 -butyric acid methyl ester ͑PCBM͒ 1:1 weight-ratio blend. We studied the effects of annealing temperature and time on the device performance for devices annealed before and after cathode deposition. Thermal annealing shows significant improvement in the performance for both types of annealing conditions, with postproduction annealing being slightly better. For devices with a 43-nm-thick active layer, maximum power conversion efficiency ͑PCE͒ of 3.2% and fill factor up to 67% is achieved under Air Mass 1.5, 100-mW/ cm 2 illumination. We performed atomic force microscopy and ultraviolet-visible absorption spectroscopy on the P3HT:PCBM films to explain the effect of thermal annealing. By keeping the optimized thermal annealing condition and by varying the active layer thickness, we fabricated devices with PCE up to 4.0%, which is the highest efficiency reported so far for this system.
Advancement in P3HT PCBM solar cells, the most efficient Polymer Photovoltaic cell
Concern about global warming and diminishing fossil fuel reserves have accelerated searches for low cost sources of renewable energy. Organic photovoltaic (OPV) cells are one such source. They have couple of advantages over the conventional semiconductors. Organic solar cells have the potential to be low cost and efficient solar energy convertors, with a promising energy balance. The applications of thermoelectric polymers at low temperatures, especially conducting polymers, have shown various advantages such as easy and low cost of fabrication, light weight, and flexibility. However efficiency remains quite low. Thus efforts have been made to increase the efficiency by varying the fabrication parameters. Poly (3-hexythiophene) (P3HT) and 1-(3-methoxycarbonyl) propyl-1-phenyl [6, 6] C 61 (PCBM) are the most studied polymer blend materials around the world for bulk heterojunction structure of an organic solar cells (OSCs). This research article is a survey on tremendous literature published that exhibit solar cells based on blends of P3HT and PCBM. The basic structure of a P3HT: PCBM heterojunction solar cell and accurate methods for measurement of the power conversion efficiency (PCE) were also discussed. Standard method using Air Mass 1.5 Global (1000Wm -2 , AM1.5G) solar spectrum is advised after finding abnormalities in the PCE reported. It is noticed that optimum thickness and area of every layer in the cell structure is important. A detailed discussion on thermal annealing and solvent annealing approaches to improve device performance is presented. The effects of these two approaches on improving polymer crystallinity, light absorption in the polymer, carrier transport, and blend film nano-morphology, etc. are summarized. Polymer morphology has proven to be extremely important in determining the optoelectronic properties in polymer-based devices. We also investigate the effects of polymer morphology too on the PCE of the cell. Another important parameter affecting the efficiency discussed is the Molecular weight ratio of P3HT and PCBM blend active layer. Future directions and challenges on polymer solar cell development are also discussed Keywords— P3HT: PCBM organic blend layer, Polymer Photovoltaic, Organic solar cells, bulk heterojunctions.
Polymer International, 2008
BACKGROUND: The highest efficiencies of bulk-heterojunction solar cells from poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C 61 -butyric acid methyl ester (PCBM) reported so far are close to 6%. Phenomena occurring during the photovoltaic process, such as the creation, diffusion and separation of excitons, as well as charge carrier transport, are governed by the active layer morphology. The latter phenomenon, which depends on the self-organization of P3HT, can be influenced by its degree of regioregularity. The aim of this work is to clarify the relationship between the regioregularity of P3HT, the composition of P3HT/PCBM blends and the performances of photovoltaic devices.
Advanced Energy Materials, 2018
Poly (3-hexylthiophene) was an early frontrunner in the development of donor polymers to be used in organic photovoltaics. A relatively straightforward and inexpensive synthesis suggests that it may be the most viable donor polymer to use in large-scale commercial organic solar cells. Replacing fullerenes with new electron acceptors has led to significant improvements in device performance and stability, with devices now able to exceed an efficiency of 7%. Past studies have reported a dependence of device performance on the molecular weight of the polymer in fullerene-containing blends, however, with nonfullerene acceptors now showing promise a similar study was needed. P3HT blends, with two nonfullerene acceptors (O-IDTBR and EH-IDTBR), were probed using a number of polymer batches with varying molecular weights. O-IDTBR was shown to exhibit a dependence on the polymer molecular weight, with optimal performance achieved with a 34 kDa polymer, whilst EH-IDTBR displayed an independence in performance with varying polymer molecular weight. Probing the thermal and morphological behavior of the P3HT:O-IDTBR blends suggest an optimal morphology, with pronounced donor and acceptor domains was only achieved in with the 34 kDa polymer, and a greater degree of mixing was exhibited in the other blends, likely leading to poorer device performance.
Advanced Materials, 2010
Sun is the largest carbon-neutral energy source that has not been fully utilized. Although there are solar cell devices based on inorganic semiconductor to efficiently harvest solar energy, the cost of these conventional devices is too high to be economically viable. This is the major motivation for the development of organic photovoltaic (OPV) materials and devices, which are envisioned to exhibit advantages such as low cost, flexibility, and abundant availability. The past success in organic light-emitting diodes provides scientists with confidence that organic photovoltaic devices will be a vital alternate to the inorganic counterpart.