| 1. |
- George, Zandra, 1985, et al.
(författare)
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Two-in-one : Cathode modification and improved solar cell blend stability through addition of modified fullerenes
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:7, s. 2663-2669
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of dual purpose modified fullerenes with pyridine-as well as amine-functional groups is reported. Addition of these fullerenes to a polymer : fullerene bulk-heterojunction blend based on a thiophene-quinoxaline donor polymer is found to modify the active layer/cathode interface of inverted solar cells (glass/ITO/active layer/MoO3/Al). In particular the open-circuit voltage of devices is increased from 0.1 V to about 0.7 V, which results in a drastic rise in photovoltaic performance with a power conversion efficiency of up to 3%. At the same time, presence of the functionalised fullerene additives prevents the detrimental formation of micrometre-sized fullerene crystals upon annealing at 140 degrees C. As a result, the device performance is retained, which promises significantly increased thermal stability of the bulk-heterojunction blend nanostructure.
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| 2. |
- Wang, Chuanfei, et al.
(författare)
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Low Band Gap Polymer Solar Cells With Minimal Voltage Losses
- 2016
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 6:18
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Tidskriftsartikel (refereegranskat)abstract
- One of the factors limiting the performance of organic solar cells (OSCs) is their large energy losses (E loss) in the conversion from photons to electrons, typically believed to be around 0.6 eV and often higher than those of inorganic solar cells. In this work, a novel low band gap polymer PIDTT-TID with a optical gap of 1.49 eV is synthesized and used as the donor combined with PC71BM in solar cells. These solar cells attain a good power conversion efficiency of 6.7% with a high open-circuit voltage of 1.0 V, leading to the E loss as low as 0.49 eV. A systematic study indicates that the driving force in this donor and acceptor system is sufficient for charge generation with the low E loss. This work pushes the minimal E loss of OSCs down to 0.49 eV, approaching the values of some inorganic and hybrid solar cells. It indicates the potential for further enhancement of the performance of OSCs by improving their V oc since the E loss can be minimized.
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| 3. |
- Diaz de Zerio Mendaza, Amaia, 1986, et al.
(författare)
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High-Entropy Mixtures of Pristine Fullerenes for Solution-Processed Transistors and Solar Cells
- 2015
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 27:45, s. 7325-7331
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Tidskriftsartikel (refereegranskat)abstract
- The solubility of pristine fullerenes can be enhanced by mixing C60 and C70 due to the associated increase in configurational entropy. This "entropic dissolution" allows the preparation of field-effect transistors with an electron mobility of 1 cm2 V-1 s-1 and polymer solar cells with a highly reproducible power-conversion efficiency of 6%, as well as a thermally stable active layer.
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| 4. |
- Li, Wei, et al.
(författare)
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One-Step Synthesis of Precursor Oligomers for Organic Photovoltaics: A Comparative Study between Polymers and Small Molecules
- 2015
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 7:49, s. 27106-27114
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Tidskriftsartikel (refereegranskat)abstract
- Two series of oligomers TQ and rhodanine end-capped TQ-DR were synthesized using a facile one-step method. Their optical, electrical, and thermal properties and photovoltaic performances were systematically investigated and compared. The TQ series of oligomers were found to be amorphous, whereas the TQ-DR series are semicrystalline. For the TQ oligomers, the results obtained in solar cells show that as the chain length of the oligomers increases, an increase in power conversion efficiency (PCE) is obtained. However, when introducing 3-ethylrhodanine into the TQ oligomers as end groups, the PCE of the TQ-DR series of oligomers decreases as the chain length increases. Moreover, the TQ-DR series of oligomers give much higher performances compared to the original amorphous TQ series of oligomers owing to the improved extinction coefficient (epsilon) and crystallinity afforded by the rhodanine. In particular, the highly crystalline oligomer TQ5-DR, which has the shortest conjugation length shows a high hole mobility of 0.034 cm(2) V-1 s(-1) and a high PCE of 3.14%, which is the highest efficiency out of all of the six oligomers. The structure-property correlations for all of the oligomers and the TQ1 polymer demonstrate that structural control of enhanced intermolecular interactions and crystallinity is a key for small molecules/oligomers to achieve high mobilities, which is an essential requirement for use in OPVs.
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| 5. |
- Li, Zhaojun, 1989, et al.
(författare)
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High Performance All-Polymer Solar Cells by Synergistic Effects of Fine-Tuned Crystallinity and Solvent Annealing.
- 2016
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 138:34, s. 10935-44
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Tidskriftsartikel (refereegranskat)abstract
- Growing interests have been devoted to the design of polymer acceptors as potential replacement for fullerene derivatives for high-performance all polymer solar cells (all-PSCs). One key factor that is limiting the efficiency of all-PSCs is the low fill factor (FF) (normally
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| 6. |
- Qian, D. P., et al.
(författare)
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Modulating molecular aggregation by facile heteroatom substitution of diketopyrrolopyrrole based small molecules for efficient organic solar cells
- 2015
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 3:48, s. 24349-24357
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Tidskriftsartikel (refereegranskat)abstract
- In conjugated polymers and small molecules of organic solar cells, aggregation induced by intermolecular interactions governs the performance of photovoltaics. However, little attention has been paid to the connection between molecular structure and aggregation within solar cells based on soluble small molecules. Here we demonstrate modulation of intermolecular aggregation of two synthesized molecules through heteroatom substitution to develop an understanding of the role of aggregation in conjugated molecules. Molecule 1 (M1) based on 2-ethylhexyloxy-benzene substituted benzo[1,2-b:4,5-b']dithiophene (BDTP) and diketopyrrolopyrrole (DPP) displays strong aggregation in commonly used organic solvents, which is reduced in molecule 2 (M2) by facile oxygen atom substitution on the BDTP unit confirmed by absorption spectroscopy and optical microscopy, while it successfully maintains molecular planarity and favorable charge transport characteristics. Solar cells based on M2 exhibit more than double the photocurrent of devices based on M1 and yield a power conversion efficiency of 5.5%. A systematic investigation of molecular conformation, optoelectronic properties, molecular packing and crystallinity as well as film morphology reveals structure dependent aggregation responsible for the performance difference between the two conjugated molecules.
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| 7. |
- Wang, Chuanfei, 1986-, et al.
(författare)
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Ternary Organic Solar Cells with Minimum Voltage Losses
- 2017
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 7:21
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Tidskriftsartikel (refereegranskat)abstract
- A new strategy for designing ternary solar cells is reported in this paper. A low-bandgap polymer named PTB7-Th and a high-bandgap polymer named PBDTTS-FTAZ sharing the same bulk ionization potential and interface positive integer charge transfer energy while featuring complementary absorption spectra are selected. They are used to fabricate efficient ternary solar cells, where the hole can be transported freely between the two donor polymers and collected by the electrode as in one broadband low bandgap polymer. Furthermore, the fullerene acceptor is chosen so that the energy of the positive integer charge transfer state of the two donor polymers is equal to the energy of negative integer charge transfer state of the fullerene, enabling enhanced dissociation of all polymer donor and fullerene acceptor excitons and suppressed bimolecular and trap assistant recombination. The two donor polymers feature good miscibility and energy transfer from high-bandgap polymer of PBDTTS-FTAZ to low-bandgap polymer of PTB7-Th, which contribute to enhanced performance of the ternary solar cell.
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| 8. |
- Xia, Yuxin, et al.
(författare)
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Inverted all-polymer solar cells based on a quinoxaline-thiophene/naphthalene-diimide polymer blend improved by annealing
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:10, s. 3835-3843
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the effect of thermal annealing on the photovoltaic parameters of all-polymer solar cells based on a quinoxaline-thiophene donor polymer (TQ1) and a naphthalene diimide acceptor polymer (N2200). The annealed devices show a doubled power conversion efficiency compared to nonannealed devices, due to the higher short-circuit current (J(sc)) and fill factor (FF), but with a lower open circuit voltage (V-oc). On the basis of the morphology-mobility examination by several scanning force microscopy techniques, and by grazing-incidence wide-angle X-ray scattering, we conclude that better charge transport is achieved by higher order and better interconnected networks of the bulk heterojunction in the annealed active layers. The annealing improves charge transport and extends the conjugation length of the polymers, which do help in charge generation and meanwhile reduce recombination. Photoluminescence, electroluminescence, and light intensity dependence measurements reveal how this morphological change affects charge generation and recombination. As a result, the J(sc) and FF are significantly improved. However, the smaller band gap and the higher HOMO level of TQ1 upon annealing causes a lower V-oc. The blend of an amorphous polymer TQ1, and a semi-crystalline polymer N2200, can thus be modified by thermal annealing to double the power conversion efficiency.
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| 9. |
- Ajjan Godoy, Fátima Nadia
(författare)
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Biohybrid Polymer Electrodes for Renewable Energy Storage
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Daily and seasonally fluctuating energy supply and demand requires adequate energy storage solutions. In recent years electrochemical supercapacitors have attracted considerable attention due to their ability to both store and deliver electrical energy efficiently. Our efforts are focused on developing and optimizing sustainable organic electrode materials for supercapacitors based on renewable bioorganic materials, offering a cheap, environmentally friendly and scalable alternative to store energy. In particular, we are using the second most abundant biopolymer in nature, lignin (Lig), which is an insulating material. However, when used in combination with electroactive and conducting polymers such as polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), the biohybrid electrodes PPy/Lig and PEDOT/Lig display significantly enhanced energy storage performance as compared to the pristine conducting polymers without the lignin. Redox cyclic voltammetry and galvanostatic charge/discharge measurements indicate that the enhanced performance is due to the additional pseudocapacitance generated by the quinone moieties in lignin. Moreover, a conjugated redoxpolymer poly(aminoanthraquinone) PAAQ, with intrinsic quinone functions and excellentstability, has been combined with lignin and PEDOT resulting in a trihybrid bioelectrode. PEDOT compensates the low conductivity of PAAQ and provides electrical pathways to the quinone groups. The electrochemically generated quinones undergo a two electron, two protonredox process within the biohybrid electrodes as revealed by FTIR spectroelectrochemistry.These remarkable features reveal the exciting potential of a full organic energy storage device with long cycle life. Therefore, supercapacitor devices were designed in symmetric or asymmetric two electrode configuration. The best electrochemical performance was achieved by the asymmetric supercapacitor based on PEDOT+Lignin/PAAQ as the positive electrode and PEDOT/PAAQ as the negative electrode. This device exhibits superior electrochemical performance and outstanding stability after 10000 charge/discharge cycles due to the synergistic effect of the two electrodes. Finally, we have characterized the response of this supercapacitor device when charged with the intermittent power supply from an organic photovoltaic module. We have designed charging/discharging conditions such that reserve power was available in the storage device at all times. This work has resulted in an inexpensive fully organic system witht he dual function of energy conversion and storage.
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| 10. |
- Bergqvist, Jonas, et al.
(författare)
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Asymmetric photocurrent extraction in semitransparent laminated flexible organic solar cells
- 2018
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Ingår i: npj Flexible Electronics. - : Springer Science and Business Media LLC. - 2397-4621. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- Scalable production methods and low-cost materials with low embodied energy are key to success for organic solar cells. PEDOT(PSS) electrodes meet these criteria and allow for low-cost and all solution-processed solar cells. However, such devices are prone to shunting. In this work we introduce a roll-to-roll lamination method to construct semitransparent solar cells with a PEDOT(PSS) anode and an polyethyleneimine (PEI) modified PEDOT(PSS) cathode. We use the polymer:PCBM active layer coated on the electrodes as the lamination adhesive. Our lamination method efficiently eliminates any shunting. Extended exposure to ambient degrades the laminated devices, which manifests in a significantly reduced photocurrent extraction when the device is illuminated through the anode, despite the fact that the PEDOT(PSS) electrodes are optically equivalent. We show that degradation-induced electron traps lead to increased trap-assisted recombination at the anode side of the device. By limiting the exposure time to ambient during production, degradation is significantly reduced. We show that lamination using the active layer as the adhesive can result in device performance equal to that of conventional sequential coating.
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