| 1. |
- Guo, Xuewen, et al.
(author)
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Novel small-molecule zwitterionic electrolyte with ultralow work function as cathode modifier for inverted polymer solar cells
- 2018
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In: Organic electronics. - : ELSEVIER SCIENCE BV. - 1566-1199 .- 1878-5530. ; 59, s. 15-20
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Journal article (peer-reviewed)abstract
- Interfacial compatibility between the electrode and organic semiconductor plays a critical role in controlling the charge transport and hence efficiency of organic solar cell. Here, we introduce a novel small-molecule zwitterionic electrolyte (S1) combined with ZnO as electron transporting interlayer employed for the inverted PTB7:PC71BM bulk heterojunction solar cell. The resulting device with the S1/ZnO stacked interlayer achieves a high PCE of 8.59%, obtaining a 16.2% improvement over the control device performance of 7.4% without the S1 attributed to the significant increased short-circuit current density and fill factor. The interfacial properties are investigated. It is found that the S1/ZnO interlayer possess an ultralow work function of 3.6 eV, which originates from the interfacial double dipole step induced by the zwitterionic side chain electrostatic realignment at interface. The S1/ZnO interlayer exhibits the excellent charge extraction ability, suppresses the charge recombination loss and decreases the series resistance at the active layer/electrode contact.
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| 2. |
- Guo, Xuewen, et al.
(author)
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Understanding the effect of N2200 on performance of J71 : ITIC bulk heterojunction in ternary non-fullerene solar cells
- 2019
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In: Organic electronics. - : Elsevier. - 1566-1199 .- 1878-5530. ; 71, s. 65-71
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Journal article (peer-reviewed)abstract
- None-fullerene solar cells with ternary architecture have attracted much attention because it is an effective approach for boosting the device power conversion efficiency. Here, the crystalline polymer N2200 as the third component is integrated into J71: ITIC bulk heterojunction. A series of characterizations indicate that N2200 could increase photo-harvesting, balanced hole and electron mobilities, enhanced exciton dissociation, and suppressed charge recombination, which result in the comprehensive improvement of open circuit voltage, short circuit current and fill factor in the device. Moreover, after introduction of N2200, the morphology of the ternary active layer is optimized, and the film crystallinity is improved. This work demonstrates that adding a small quantity of high crystallization acceptor into non-fullerene donor: acceptor mixture is a promising strategy toward developing high-performance organic solar cells.
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| 3. |
- Xiong, Shaobing, et al.
(author)
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Engineering of the Back Contact between PCBM and Metal Electrode for Planar Perovskite Solar Cells with Enhanced Efficiency and Stability
- 2019
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In: Advanced Optical Materials. - : WILEY-V C H VERLAG GMBH. - 2162-7568 .- 2195-1071. ; 7:19
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Journal article (peer-reviewed)abstract
- The cathode interface plays a critical role in achieving high-performance fullerene/perovskite planar solar cells. Herein, the simple molecule Isatin and its derivatives are introduced at the back contact [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)/Al as a cathode modification interlayer. It is revealed that the Isatin interlayers facilitate electron transport/extraction and suppress electron recombination, attributed to the formation of negative dipole potential steps and the passivation of the interfacial trap density. The average power conversion efficiencies of the resulting devices are significantly improved by 11% from 17.68% to 19.74%, with an enhancement in all device parameters including short-circuit current, open-circuit voltage, and fill factor. The hysteresis index is found to disappear. In addition, such interlayer enhances device stability under ambient conditions compared to the control devices due to suppression of moisture-induced degradation of the perovskite films. These findings provide a comprehensive understanding of the engineering of the back contact between PCBM and the metal electrode to improve efficiency and stability of perovskite solar cells.
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| 4. |
- Yang, Jianming, et al.
(author)
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Extremely Low-Cost and Green Cellulose Passivating Perovskites for Stable and High-Performance Solar Cells
- 2019
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 11:14, s. 13491-13498
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Journal article (peer-reviewed)abstract
- The fast evolution of metal halide perovskite solar cells has opened a new chapter in the field of renewable energy. High-quality perovskite films as the active layers are essential for both high efficiency and long-term stability. Here, the perovskite films with enlarged crystal grain size and decreased defect density are fabricated by introducing the extremely low-cost and green polymer, ethyl cellulose (EC), into the perovskite layer. The addition of EC triggers hydrogen bonding interactions between EC and the perovskite, passivating the charge defect traps at the grain boundaries. The long chain of EC further acts as a scaffold for the perovskite structure, eliminating the annealing-induced lattice strain during the film fabrication process. The resulting devices with the EC additive exhibit a remarkably enhanced average power conversion efficiency from 17.11 to 19.27% and an improvement of all device parameters. The hysteresis index is found to decrease by three times from 0.081 to 0.027, which is attributed to suppressed ion migration and surface charge trapping. In addition, the defect passivation by EC significantly improves the environmental stability of the perovskite films, yielding devices that retain 80% of their initial efficiency after 30 days in ambient air at 45% relative humidity, whereas the pristine devices without EC fully degrade. This work provides a low-cost and green avenue for passivating defects that improves both the efficiency and operational stability of perovskite solar cells.
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| 5. |
- Yang, Jianming, et al.
(author)
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Unraveling Photostability of Mixed Cation Perovskite Films in Extreme Environment
- 2018
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In: Advanced Optical Materials. - : WILEY-V C H VERLAG GMBH. - 2162-7568 .- 2195-1071. ; 6:20
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Journal article (peer-reviewed)abstract
- Organometal halide perovskites exhibit a bright future for applications in solar cells, as efficiency has achieved over 22%. The long-term stability remains a major obstacle for commercialization. Here, it is found that three cationic compositional engineered perovskites, MAPb(I0.83Br0.17)(3), FA(0.83)MA(0.17)Pb(I0.83Br0.17)(3), and Cs-0.1(FA(0.83)MA(0.17))(0.9)Pb(I0.83Br0.17)(3), undergo severe degradation under white-light illumination in ultrahigh vacuum (UHV) environment, but the rate of degradation is significantly lower for the mixed cation perovskites. This is attributed to the defect-induced trap states that trigger the strong coupling between the photoexcited carriers and the crystal lattice. The observed behavior supports the view of the mixed cations suppressing the photoinduced degradation. It is further demonstrated that UHV environment remarkably accelerates the degradation of the perovskite films under illumination, which delivers a very important message that the current hybrid perovskite materials and their optoelectronic devices are not suitable for application in outer space. Moreover, the applied UHV environment can be an accelerated test method to estimate the photostability of the perovskites.
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