| 1. |
- Chen, Shangshang, et al.
(författare)
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Efficient Nonfullerene Organic Solar Cells with Small Driving Forces for Both Hole and Electron Transfer
- 2018
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 30:45
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Tidskriftsartikel (refereegranskat)abstract
- State-of-the-art organic solar cells (OSCs) typically suffer from large voltage loss (V-loss) compared to their inorganic and perovskite counterparts. There are some successful attempts to reduce the V-loss by decreasing the energy offsets between the donor and acceptor materials, and the OSC community has demonstrated efficient systems with either small highest occupied molecular orbital (HOMO) offset or negligible lowest unoccupied molecular orbital (LUMO) offset between donors and acceptors. However, efficient OSCs based on a donor/acceptor system with both small HOMO and LUMO offsets have not been demonstrated simultaneously. In this work, an efficient nonfullerene OSC is reported based on a donor polymer named PffBT2T-TT and a small-molecular acceptor (O-IDTBR), which have identical bandgaps and close energy levels. The Fourier-transform photocurrent spectroscopy external quantum efficiency (FTPS-EQE) spectrum of the blend overlaps with those of neat PffBT2T-TT and O-IDTBR, indicating the small driving forces for both hole and electron transfer. Meanwhile, the OSCs exhibit a high electroluminescence quantum efficiency (EQE(EL)) of approximate to 1 x 10(-4), which leads to a significantly minimized nonradiative V-loss of 0.24 V. Despite the small driving forces and a low V-loss, a maximum EQE of 67% and a high power conversion efficiency of 10.4% can still be achieved.
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| 2. |
- Liu, Jing, et al.
(författare)
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Fast charge separation in a non-fullerene organic solar cell with a small driving force
- 2016
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Ingår i: NATURE ENERGY. - : NATURE PUBLISHING GROUP. - 2058-7546. ; 1
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Tidskriftsartikel (refereegranskat)abstract
- Fast and efficient charge separation is essential to achieve high power conversion efficiency in organic solar cells (OSCs). In state-of-the-art OSCs, this is usually achieved by a significant driving force, defined as the offset between the bandgap (E-gap) of the donor/acceptor materials and the energy of the charge transfer (CT) state (E-CT), which is typically greater than 0.3 eV. The large driving force causes a relatively large voltage loss that hinders performance. Here, we report non-fullerene OSCs that exhibit ultrafast and efficient charge separation despite a negligible driving force, as E-CT is nearly identical to E-gap. Moreover, the small driving force is found to have minimal detrimental effects on charge transfer dynamics of the OSCs. We demonstrate a non-fullerene OSC with 9.5% efficiency and nearly 90% internal quantum efficiency despite a low voltage loss of 0.61V. This creates a path towards highly efficient OSCs with a low voltage loss.
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| 3. |
- Zhao, Jingbo, 1989-, et al.
(författare)
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Color Segmentation on FPGA Using Minimum Distance Classifier for Automatic Road Sign Detection
- 2012
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Ingår i: IST 2012 - 2012 IEEE International Conference on Imaging Systems and Techniques, Proceedings. - : IEEE conference proceedings. - 9781457717765 ; , s. 516-521
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Konferensbidrag (refereegranskat)abstract
- Classification is an important step in machine vision systems; it reveals the true identity of an object using features extracted in pre-processing steps. Practical usage requires the operation to be fast, energy efficient and easy to implement. In this paper, we present a design of minimum distance classifier based on FPGA platform. It is optimized by the pipelined structure to strike a balance between the device utilization and computational speed. In addition, the dimension of the feature space is modeled as generic parameter, making it possible for the design to re-generate hardware to cope with feature space with arbitrary dimensions. Its primary application is demonstrated on color segmentation on FPGA in the form of efficient classification using color as features. This result is further extended by introducing a multi-class component labeling module to label the segmented color components and measure the geometric properties of them. The combination of these two modules can effectively detect road signs as region of interests.
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