Knowing the correlation of reaction parameters in the preparing process of carbon dots (CDs) is essential for optimizing the synthesis strategy, exploring exotic properties, and exploiting potential applications. However, the integrated screening experimental data on the synthesis of CDs are huge and noisy. Machine learning (ML) has recently been successfully used
The electro-mechanical (EM) impedance method is gradually emerging as a widely accepted technique for structural health monitoring and systems identification. The method utilizes smart piezoceramic (PZT) transducers intimately bonded to the surface of a structural substrate. Through the unique electro-mechanical properties of the PZT transducers, the presence of damage, as well as the dynamical properties of the host structure are captured and reflected in the electrical admittance response. In the present work, the effect of the bond layer on the electro-mechanical response of a smart system is being studied. Experiments with the EM impedance method were performed on laboratory-sized beams. Consequently, the effects of shear lag due to the finite thickness bond layer were successfully identified. This was followed by the theoretical analysis of shear lag effects. It was found that the induced strain behaviour of the structural specimen in question is inevitably modified by the presence of shear lag between the PZT transducer and the structural substrate. Subsequently, the EM admittance response of the beam specimens were simulated based on the results gathered from the theoretical analysis. Incidentally, it was found that the theoretical model clearly depicts the trends of the measured response.
5,2,5]thiadiazole (FBT)-based conjugated donor−acceptor (D-A) polymers with straight and branched side chains were synthesized via Stille-coupling copolymerization to study their physical, optoelectronic and photovoltaic properties. The results show that both the nature of pendant side chains and the electron acceptor strength of the acceptor moiety of D−A polymers have critical impacts on material and photovoltaic properties. Better π−π stacking of polymer backbones enabled by appropriate substituents such as fluorine atoms and branched alkyl chains leads to a reasonably high power conversion efficiency of over 6% when the polymer is utilized as a donor material with PC71BM as an active layer in bulk heterojunction solar cells.
A novel conjugated polymer PIDTT-quinoxaline (Qx) based on the coplanar thieno[3,2-b]thiophene-phenylene-thieno[3,2-b]thiophene structure is synthesized and evaluated as an electron-donor material for bulk-heterojunction polymer solar cells (BHJ PSCs). The absorption spectra, electrochemical, charge transport, and film morphology properties as well as theoretical modeling of PIDTT-Qx are investigated to understand its intrinsic structure-property relationship. As expected, this polymer with an extended π-conjugated backbone exhibits a narrow-bandgap and board absorption spectrum for enhanced light harvesting. BHJ PSCs (ITO/PEDOT:PSS/polymer:PC71 BM/interlayer/Al) afford a maximum power conversion efficiency of 5.05% with an open-circuit voltage of 0.84 V, a short-circuit current density of 11.26 mA cm(-2) , and a fill factor of 53.4%. These results demonstrate the potential of PIDTT-Qx as an efficient electron-donor material for BHJ PSCs.
The interpenetrating morphology formed by the electron donor and acceptor materials is critical for the performance of polymer:fullerene bulk heterojunction (BHJ) photovoltaic (PV) cells. In this work we carried out a systematic investigation on a high PV efficiency (>6%) BHJ system consisting of a newly developed 5,6-difluorobenzo[c]125 thiadiazole-based copolymer, PFBT-T20TT, and a fullerene derivative. Grazing incidence X-ray scattering measurements reveal the lower-ordered nature of the BHJ system as well as an intermixing morphology with intercalation of fullerene molecules between the PFBT-T20TT lamella. Steady-state and transient photo-induced absorption spectroscopy reveal ultrafast charge transfer (CT) at the PFBT-T20TT/fullerene interface, indicating that the CT process is no longer limited by exciton diffusion. Furthermore, we extracted the hole mobility based on the space limited current (SCLC) model and found that more efficient hole transport is achieved in the PFBT-T20TT:fullerene BHJ as compared to pure PFBT-T20TT, showing a different trend as compared to the previously reported highly crystalline polymer:fullerene blend with a similar intercalation manner. Our study correlates the fullerene intercalated polymer lamella morphology with device performance and provides a coherent model to interpret the high photovoltaic performance of some of the recently developed weakly-ordered BHJ systems based on conjugated polymers with branched side-chain.
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