5 Search Results

Photovoltaic performance modeling accuracy depends heavily on the quality of the input parameters. When relying on generic PAN files and datasheets, the input parameters often fail to accurately capture the behavior of every module with the same model number. Therefore, there is a need for methods to generate more accurate input data. In this study, we present a method for determining parameter values for the PVsyst version 6 photovoltaic module performance model from performance test measurements following the IEC 61853-1:2011 standard. The method is intentionally noniterative to facilitate implementation and reproducibility. We apply the method to datasets from 15 modulesmore » of various photovoltaic technologies (SHJ, TOPCon, IBC, PERC, n-PERT, Al-BSF, and CdTe), reproducing the original maximum power measurements with root-mean-squared (RMS) accuracy within 0.5% in all cases. The method's accuracy is compared to that of two iterative methods.« less

In this study, optically generated molecular spin centers offer an attractive platform for room-temperature spintronic and quantum applications. The linear acene family of molecules are especially good candidates due to their efficient generation of highly polarized triplet excitons via singlet fission. However, the direct detection and manipulation of these spin centers in thin films via the electrical means desirable for ultimate microelectronic devices has proven challenging. In particular, highly oriented triplet features have previously been detected in crystalline anthracene but longer acenes reveal only doublet features in Electrically-Detected Magnetic Resonance (EDMR). In this work we present EDMR spectra of highlymore » oriented triplet excitons in pentacene for the first time, using a host-guest style device made of tetracene and pentacene. The guest acts as an energetic trap site, permitting the isolation and detection of molecular triplets at room temperature. Modeling of these results shows that the observed resonance features correspond to triplet sublevel transitions on isolated pentacene guest molecules. Rotation of the applied field confirms the tendency of the linear acenes to self-orient with the longest molecular axis perpendicular to the device substrate. Lastly, we find the disappearance of resonant triplet features in the neat acenes is not primarily due to the effects of exciton delocalization, but a broader mechanism of spin relaxation primarily influenced by exciton diffusivity.« less

Layered two-dimensional (2D) materials such as MoS₂ have attracted much attention for nano- and opto-electronics. Recently, intercalation (e.g. of ions, atoms, or molecules) has emerged as an effective technique to modulate material properties of such layered 2D films reversibly. We probe both the electrical and thermal properties of Li-intercalated bilayer MoS₂ nanosheets by combining electrical measurements and Raman spectroscopy. Furthermore, we demonstrate reversible modulation of carrier density over more than two orders of magnitude (from 0.8 × 10¹² to 1.5 × 10¹⁴ cm^-2), and we simultaneously obtain the thermal boundary conductance between the bilayer and its supporting SiO₂ substrate formore » an intercalated system for the first time. This thermal coupling can be reversibly modulated by nearly a factor of eight, from 14 ± 4.0 MW m^-2 K^-1 before intercalation to 1.8 ± 0.9 MW m^-2 K^-1 when the MoS₂ is fully lithiated. These results reveal electrochemical intercalation as a reversible tool to modulate and control both electrical and thermal properties of 2D layers.« less

With angle-resolved photoemission spectroscopy, we studied the electronic structure of TaFe₁̣₂₃Te₃, a two-leg spin ladder compound with a novel antiferromagnetic ground state. Quasi-two-dimensional Fermi surface is observed, with sizable inter-ladder hopping. Moreover, instead of observing an energy gap at the Fermi surface in the antiferromagnetic state, we observed the shifts of various bands. Combining these observations with density-functional-theory calculations, we propose that the large scale reconstruction of the electronic structure, caused by the interactions between coexisting itinerant electrons and local moments, is most likely the driving force of the magnetic transition. Thus TaFe₁̣₂₃Te₃ serves as a simpler platform that containsmore » similar ingredients as the parent compounds of iron-based superconductors.« less

We performed magneto-optical (MO) measurements on FeTe₀̣₅Se₀̣₅ thin films grown on LaAlO₃ (LAO) and Yttria-stabilized zirconia (YSZ) single-crystalline substrates. These thin films show superconducting transition temperature T_c ~19 K, 4 K higher than the bulk sample. Typical roof-top patterns can be observed in the MO images of thin films grown on LAO and YSZ, from which a large and homogeneous critical current density J_c ~ 3 - 4 x 10⁶ A/cm² at 5 K was obtained. In this study, magnetic flux penetration measurement reveals that the current is almost isotropically distributed in the two thin films. Compared with bulk crystals,more » FeTe₀̣₅Se₀̣₅ thin film demonstrates not only higher T_c, but also much larger J_c, which is attractive for applications.« less