Semitransparent Perovskite Solar Cells with an Evaporated Ultra-Thin Perovskite Absorber

Metal halide perovskites are of great interest for application in semitransparent solar cells due to their tunable bandgap and high performance. However, fabricating high-efficiency perovskite semitransparent devices with high average visible transmittance (AVT) is challenging because of their high absorption coefficient. Here, a co-evaporation process is adopted to fabricate ultra-thin CsPbI3 perovskite films. The smooth surface and orientated crystal growth of the evaporated perovskite films make it possible to achieve 10 nm thin films with compact and continuous morphology without pinholes. When integrated into a p-i-n device structure of glass/ITO/PTAA/perovskite/PCBM/BCP/Al/Ag with an optimized transparent electrode, these ultra-thin layers result in an impressive open-circuit voltage (VOC) of 1.08 V and a fill factor (FF) of 80%. Consequently, a power conversion efficiency (PCE) of 3.6% with an AVT above 50% is demonstrated, which is the first report for a perovskite device of a 10 nm active layer thickness with high VOC, FF and AVT. These findings demonstrate that deposition by thermal evaporation makes it possible to form compact ultra-thin perovskite films, which are of great interest for future smart windows, light-emitting diodes, and tandem device applications

Strong light-matter coupling for reduced photon energy losses in organic photovoltaics

Funding: Volkswagen Foundation (no.93404) (MCG), individual fellowship of the DeutscheForschungsgemeinschaft (404587082) (AM).Strong light-matter coupling can re-arrange the exciton energies in organic semiconductors. Here, we exploit strong coupling by embedding a fullerene-free organic solar cell (OSC) photo-active layer into an optical microcavity, leading to the formation of polariton peaks and a red-shift of the optical gap. At the same time, the open-circuit voltage of the device remains unaffected. This leads to reduced photon energy losses for the low-energy polaritons and a steepening of the absorption edge. While strong coupling reduces the optical gap, the energy of the charge-transfer state is not affected for large driving force donor-acceptor systems. Interestingly, this implies that strong coupling can be exploited in OSCs to reduce the driving force for electron transfer, without chemical or microstructural modifications of the photo-active layer. Our work demonstrates that the processes determining voltage losses in OSCs can now be tuned, and reduced to unprecedented values, simply by manipulating the device architecture.Publisher PDFPeer reviewe

Research on Ultra-Wideband NLFM Waveform Synthesis and Grating Lobe Suppression

Ultra-wideband (UWB) nonlinear frequency modulation (NLFM) waveforms have the advantages of low sidelobes and high resolution. By extending the frequency domain wideband synthesis method to the NLFM waveform, the synthetic bandwidth will be limited, and the grating lobe will grow as the number of subpulses increases at a fixed synthetic bandwidth. Aiming for the highly periodic grating lobes caused by equally spaced splicing and small subpulse time-bandwidth products (TxBW), a multisubpulse UWB NLFM waveform synthesis method is proposed in this paper. Random frequency hopping and spectral correction are utilized to disperse the energy of periodic grating lobes and optimize the matched filter of the subpulse, thereby reducing notches and Fresnel ripples in the synthesized spectrum. The results of the hardware-in-the-loop simulation experiment show that the peak sidelobe ratio (PSLR) and the integral sidelobe ratio (ISLR) of the NLFM synthetic wideband waveform (SWW) obtained by 50 subpulses with a bandwidth of 36 MHz are improved by 4.8 dBs and 4.5 dBs, respectively, when compared to the frequency domain wideband synthesis method, and that the grating lobe is suppressed by an average of 10.6 dBs. It also performs well in terms of point target resolution, and it has potential for 2D radar super-resolution imaging

A New BiRNN-SVA Method for Side Lobe Suppression

The spatially variant apodization (SVA) algorithm, a classic super-resolution method for synthetic aperture radar (SAR) images, can suppress side lobes while maintain the resolution of the main lobe. To address the problem of residual side lobes or loss of main lobe energy in improved SVA algorithms, the article proposes a new side lobe suppression method combining the bidirectional recurrent neural network (BiRNN) and the SVA algorithm, employing BiRNN to extract the main lobe and side lobe features of radar data to achieve side lobe suppression at any Nyquist sampling rate. The land flight experiment data of the fully polarized microwave scatterometer is used to quantitatively evaluate the side lobe suppression performance and the main lobe energy in order to verify the effectiveness of the BiRNN-SVA method. The experimental results demonstrate that the BiRNN-SVA method can be applied to data at any Nyquist sampling rate and has superior PSLR and ISLR compared to the GSVA algorithm and MSVA algorithm. The image processed with the proposed method retains more fine details and edge features. In comparison to the GSVA algorithm and MSVA algorithm, the image contrast and focus have increased by 31.6% and 3.6%, respectively, and by 4.4% and 1.1%

Echo-Level SAR Imaging Simulation of Wakes Excited by a Submerged Body

The paper introduces a numerical simulation method for Synthetic Aperture Radar (SAR) imaging of submerged body wakes by integrating hydrodynamics, electromagnetic scattering, and SAR imaging simulation. This work is helpful for better understanding SAR images of submerged body wakes. Among these, the hydrodynamic model consists of two sets of ocean dynamics closely related to SAR imaging, namely the wake of the submerged body and wind waves. For the wake, we simulated it using computational fluid dynamics (CFD) numerical methods. Furthermore, we compared and computed the electromagnetic scattering characteristics of wakes under various navigation parameters and sea surface conditions. Following that, based on the operational principles and imaging theory of synthetic aperture radar (SAR), we established the SAR raw echo signal of the wake. Employing a Range-Doppler (RD) algorithm, we generated simulated SAR images of the wake. The results indicate that utilizing Computational Fluid Dynamics (CFD) numerical methods enables the simulation of wake characteristics generated by the motion of a submerged body with different velocities. The backscattering features of wakes are closely associated with the relative orientation between the wake and the radar line of sight. Under specific wind speeds, the wake gets masked within the sea surface background, resulting in less discernible characteristics of the wake in SAR images. This suggests that at lower speeds of submerged body or under specific wind conditions, the detectability of the wake in SAR images significantly diminishes

Solvating power regulation enabled low concentration electrolyte for lithium batteries

Li+ solvation structures have a decisive influence on the electrode/electrolyte interfacial properties and battery performances. Reduced salt concentration may result in an organic rich solid electrolyte interface (SEI) and catastrophic cycle stability, which makes low concentration electrolytes (LCEs) rather challenging. Solvents with low solvating power bring in new chances to LCEs due to the weak salt-solvent interactions. Herein, an LCE with only 0.25 mol L-1 salt is prepared with fluoroethylene carbonate (FEC) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (D-2). Molecular dynamics simulations and experiments prove that the low solvating power solvent FEC not only renders reduced desolvation energy to Li+ and improves the battery kinetics, but also promotes the formation of a LiF-rich SEI that hinders the electrolyte consumption. Li||Cu cell using the LCE shows a high coulombic efficiency of 99.20%, and LiNi0.6Co0.2Mn0.2O2||Li cell also exhibits satisfying capacity retention of 89.93% in 200 cycles, which demonstrates the great potential of solvating power regulation in LCEs development. (c) 2022 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved

Solvating power regulation enabled low concentration electrolyte for lithium batteries

Li+ solvation structures have a decisive influence on the electrode/electrolyte interfacial properties and battery performances. Reduced salt concentration may result in an organic rich solid electrolyte interface (SEI) and catastrophic cycle stability, which makes low concentration electrolytes (LCEs) rather challenging. Solvents with low solvating power bring in new chances to LCEs due to the weak salt-solvent interactions. Herein, an LCE with only 0.25 mol L-1 salt is prepared with fluoroethylene carbonate (FEC) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (D-2). Molecular dynamics simulations and experiments prove that the low solvating power solvent FEC not only renders reduced desolvation energy to Li+ and improves the battery kinetics, but also promotes the formation of a LiF-rich SEI that hinders the electrolyte consumption. Li||Cu cell using the LCE shows a high coulombic efficiency of 99.20%, and LiNi0.6Co0.2Mn0.2O2||Li cell also exhibits satisfying capacity retention of 89.93% in 200 cycles, which demonstrates the great potential of solvating power regulation in LCEs development. (c) 2022 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved

Refining the Substrate Surface Morphology for Achieving Efficient Inverted Perovskite Solar Cells

10.1002/aenm.202302280Advanced Energy Material

Preparation of Magnetic Hyper-Cross-Linked Polymers for the Efficient Removal of Antibiotics from Water

A novel method for fabricating magnetic hyper-cross-linked polymers (MHCPs) with high Brunauer–Emmett–Teller (BET) specific surface area, large pore volume, and good magnetic properties was developed. The synthesis process of MHCPs included two steps: the preparation of HCPs by external cross-linker and the in situ oxidation of the iron source in the structure of HCPs. On the basis of the systematic investigation of the influences of oxidation time and amount of hydrogen peroxide added, a series of MHCPs with different specific surface area, pore volume, and magnetic responsiveness was controllably prepared with the highest BET specific surface area and maximum saturation magnetization of 729.93 m²/g and 12.4 emu/g, respectively. Furthermore, the adsorption performance of MHCPs with antibiotics was studied by using chloramphenicol (CAP) and tetracycline hydrochloride (TC) as model adsorbates. The kinetics isotherms of CAP and TC followed a pseudo-second-order model, and the adsorption isotherms of them were proved to fit the Langmuir adsorption model. The maximum adsorption capacity of CAP and TC at the temperature of 20 °C could reach 114.94 and 212.77 mg/g, respectively. The above results showed that the MHCPs would be one of the most promising candidates for application in the adsorption of antibiotics