The major losses that limit the efficiency of a single-junction solar cell are thermalization loss and transmission loss. Thus, to efficiently utilize the full solar spectrum and to mitigate these losses, tandem solar cells (TSC) have significantly impacted the photovoltaic (PV) landscape. In this context, the research on perovskite/silicon tandems is currently dominating the research community. The stability improvements of perovskite materials and mature fabrication techniques of silicon have underpinned the rapid progress of perovskite/silicon TSC. However, the low absorption coefficient and high module cost of the silicon are the tailbacks for the mass production of perovskite/silicon TSCs. Therefore, PV technology demands to explore some new materials other than Si to be used as absorber layer in the bottom cell. Thus, here in this work, to mitigate the aforementioned losses and to reduce cost, a 23.36% efficient two-terminal perovskite-PbS CQD monolithic tandem solar cell has been designed through comprehensive device simulations. Before analyzing the performance of the proposed TSC, the performance of perovskite top cells has been optimized in terms of variation in optical properties, thickness, and interface defect density under standalone conditions. Thereafter, filtered spectrum and associated integrated filtered power by the top cell at different perovskite thickness from 50 to 500 nm is obtained to conceive the presence of the top cell above the bottom cell with different perovskite thickness. The current matching by concurrently varying the thickness of both the top and bottom subcell has also been done to obtain the maximum deliverable tandem JSC for the device under consideration. The top/bottom subcell with current matched JSC of 16.68 mA cm−2/16.62 mA cm−2 showed the conversion efficiency of 14.60%/9.07% under tandem configuration with an optimized thickness of 143 nm/470 nm, where the top cell is simulated under AM1.5G spectrum, and bottom cell is exposed to the spectrum filtered by 143 nm thick top cell. Further, the voltages at equal current points are added together to generate tandem J–V characteristics. This work concludes a 23.36% efficient perovskite-PbS CQD tandem design with 1.79 V (VOC), 16.67 mA cm−2 (JSC) and 78.3% (FF). The perovskite-PbS CQD tandem device proposed in this work may pave the way for the development of high-efficiency tandem solar cells for low-cost applications.
Polycarbonate nanocomposite containing silicon oxide nanoparticles average size of 5 nm at different weight ratio has been prepared by solution mixing method. The dispersion of nanoparticles in polymer matrix was studied by transmission electron microscopy (TEM). The optical and thermally stimulated behavior of nanocomposites were analyzed by energy dispersive X-ray spectra (EDX), X-ray diffraction pattern (XRD), UV-vis spectroscopy, differential scanning calorimetry (DSC), and thermally stimulated discharge current (TSDC). TEM images show the dispersion and size of the nanoparticles, however, EDX indicate the presence of SiO 2 on the surface of the nanocomposite film. An XRD result reveals that the crystallinity increases with increase in concentration of SiO 2 nanoparticles in polymer matrix. The direct and indirect optical energy band gaps decreased and number of carbon atom increased with concentration of SiO 2 nanoparticles. We have observed that the increase of SiO 2 nanoparticles in PC significantly reduces the refractive index. DSC and TSDC show that glass transition temperature increases according to SiO 2 weight ratio. The TSDC of nanocomposites samples could be understand in terms of non-Debye theory of charge relaxation and co-tunneling mechanism of charge transport. V C 2012 Wiley Periodicals, Inc.J Appl Polym Sci 126: [960][961][962][963][964][965][966][967][968] 2012
Increasing demands for data centers, backbone, access, and wireless networks require inventive concepts to transmit and distribute digital or analog signal waveforms. We present a new, extremely simple transceiver concept, fundamentally different from conventional approaches. It does not rely on high-speed electronics and enables transmission of various time multiplexed analog waveforms or digital data signals with the maximum possible symbol rate in the same rectangular optical spectral band B. The aggregate symbol rate of N signal channels corresponds to B or twice the used modulator’s electro-optical bandwidth. By a modification of the system, it can be increased to three times the modulator bandwidth. The rectangular spectra can be further multiplexed into wavelength-superchannels without guardbands. To time demultiplex single signal channel, just another intensity modulator and a detector with an electrical bandwidth corresponding to the channel’s baseband width (B/(2N)) is required. No optical filter, high-speed signal processing, or unconventional photonic devices are needed; thus, it has the potential to be easily integrated into any platform and provides an economical and energy-efficient solution for future communication networks and microwave photonic links.
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