| 1. |
- Zhang, Tiankai, et al.
(författare)
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Ion-modulated radical doping of spiro-OMeTAD for more efficient and stable perovskite solar cells
- 2022
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Ingår i: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 377:6605, s. 495-501
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Tidskriftsartikel (refereegranskat)abstract
- Record power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have been obtained with the organic hole transporter 2,2,7,7-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9-spirobifluorene (spiro-OMeTAD). Conventional doping of spiro-OMeTAD with hygroscopic lithium salts and volatile 4-tert-butylpyridine is a time-consuming process and also leads to poor device stability. We developed a new doping strategy for spiro-OMeTAD that avoids post-oxidation by using stable organic radicals as the dopant and ionic salts as the doping modulator (referred to as ion-modulated radical doping). We achieved PCEs of >25% and much-improved device stability under harsh conditions. The radicals provide hole polarons that instantly increase the conductivity and work function (WF), and ionic salts further modulate the WF by affecting the energetics of the hole polarons. This organic semiconductor doping strategy, which decouples conductivity and WF tunability, could inspire further optimization in other optoelectronic devices.
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| 2. |
- Lin, Rui, et al.
(författare)
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An Ultra-dense Optical Comb Based DWDM-OFDM-PON System
- 2014
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Konferensbidrag (refereegranskat)abstract
- We proposed and demonstrated an ultra-dense optical comb based DWDM-OFDM-PON scheme. At the optical line terminal (OLT), a cost-effective optical frequency comb generator (OFCG) is proposed and achieved as the multi-wavelength optical source. The OFCG is capable to provide multiple channels with reconfigurable wavelength spacing for ultra-dense WDM-PON based access network. In our scheme, OFDMsignal with multi-level modulation will be encoded into the OFCG lines for the downstream transmission to enhance the spectral efficiency while the OFDM signal will be remodulated by OOK data for the upstream transmission due to its ease of implementation in optical network unit (ONU) side. In experiments, we demonstrated that 10 optical lines with 25 GHz channel spacing are generated and they were modulated by 2.5-GB/s QPSK-OFDM for the downlink signal transmission. We also demonstrated that the multiple wavelengths from the OFCG.
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| 3. |
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| 4. |
- Lin, Rui, et al.
(författare)
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Palm-shaped spectrum generation for dual-band millimeter wave and baseband signals over fiber
- 2016
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Ingår i: Optics Communications. - : Elsevier. - 0030-4018 .- 1873-0310. ; 367, s. 137-143
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Tidskriftsartikel (refereegranskat)abstract
- In order to offer abundant available bandwidth for radio access networks satisfying future 5G requirements on capacity, this paper proposes a simple and cost-effective palm-shaped spectrum generation scheme that can be used for high capacity radio over fiber (RoF) system. The proposed scheme can simultaneously generate an optical carrier used for upstream and two bands of millimeter wave (MMW) that are capable of carrying different downstream data. The experiment results show that the proposed palm-shaped spectrum generation scheme outperforms optical frequency comb (OFC) based multi-band MMW generation in terms of upstream transmission performance. Furthermore, simulation is carried out with different dual-band MMW configurations to verify the feasibility of using the proposed spectrum generation scheme in the RoF system.
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| 5. |
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| 6. |
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| 7. |
- Suo, Jiajia, et al.
(författare)
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Interfacial engineering from material to solvent : A mechanistic understanding on stabilizing alpha-formamidinium lead triiodide perovskite photovoltaics
- 2022
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Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 94
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Tidskriftsartikel (refereegranskat)abstract
- Formamidinium lead triiodide (FAPbI3) has recently been considered as the most promising candidate to achieve highly efficient perovskite solar cells (PSCs). Excitingly, the state-of-the-art highest efficiency of FAPbI3 based PSCs have reached over 25%. However, their device stability still lags behind other compositions of mixed-cation and mixed-halide perovskites. Interfacial engineering is a very powerful method to address this issue and passivation agents have been intensively developed, however there is a lack of in-depth understanding regarding the solvent selection during post-treatment. Here, we employed cyclohexylmethylammonium iodide (CMAI) as passivation agent, which is investigated using either isopropanol (IPA) or chloroform (CF) as carrier mediator to study the solvent influence on the stabilization of FAPbI3. We observed a suppressed-defect perovskite surface toward distinguished composition with 2D CMA2PbI4 domain and CMAI domain induced by IPA and CF, respectively. Remarkably, post-treatment with solution of CMAI in CF creates a strain-free environment on the perovskite surface, leading to an improved efficiency of approaching 24% and concurrently an extraordinarily stable alpha-phase FAPbI3 PSCs under operation condition, retaining 95% of its initial efficiency after 1050-hour aging. Our resulting device stability is one of the most stable FAPbI3 based PSCs reported in literature.
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| 8. |
- Suo, Jiajia, et al.
(författare)
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Multifunctional sulfonium-based treatment for perovskite solar cells with less than 1% efficiency loss over 4,500-h operational stability tests
- 2024
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Ingår i: Nature Energy. - : NATURE PORTFOLIO. - 2058-7546.
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Tidskriftsartikel (refereegranskat)abstract
- The stabilization of grain boundaries and surfaces of the perovskite layer is critical to extend the durability of perovskite solar cells. Here we introduced a sulfonium-based molecule, dimethylphenethylsulfonium iodide (DMPESI), for the post-deposition treatment of formamidinium lead iodide perovskite films. The treated films show improved stability upon light soaking and remains in the black alpha phase after two years ageing under ambient condition without encapsulation. The DMPESI-treated perovskite solar cells show less than 1% performance loss after more than 4,500 h at maximum power point tracking, yielding a theoretical T80 of over nine years under continuous 1-sun illumination. The solar cells also display less than 5% power conversion efficiency drops under various ageing conditions, including 100 thermal cycles between 25 degrees C and 85 degrees C and an 1,050-h damp heat test. Suo et al. show that sulfonium-based molecules afford formamidinium lead iodide perovskites protection against environmental stress factors, improved phase stability and solar cells retaining efficiency over 4,500-h operational stability tests.
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| 9. |
- Yuan, Mingzhi, et al.
(författare)
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Fragmentation and structural transitions of few-layer graphene under high shear stress
- 2021
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 118:21
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Tidskriftsartikel (refereegranskat)abstract
- A key factor that determines the mechanical and electrical performance of graphene-based materials and devices is how graphene behaves under extreme conditions, yet the response of few-layer graphene to high shear stress has not been investigated experimentally. Here we applied high pressure and shear to graphene powder using a rotational diamond anvil cell and studied the recovered sample with multiple means of characterization. Sustaining high pressure and shear, graphene breaks into nanometer-long clusters with generation of large number of defects. At a certain stress level, it transforms to amorphous state and carbon onions. The reduction of infrared reflectivity in the severely sheared phase indicates the decrease in conductivity. Our results unveil the shear sensitive nature of graphene, point out the effects of shear on its physical properties, and provide a potential method to manipulate this promising material.
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