Jinliang Wu

Planar-Structure Perovskite Solar Cells with Efficiency beyond 21%

Low temperature solution processed planar-structure perovskite solar cells gain great attention recently, while their power conversions are still lower than that of high temperature mesoporous counterpart. Previous reports are mainly focused on perovskite morphology control and interface engineering to improve performance. Here, this study systematically investigates the effect of precise stoichiometry, especially the PbI2 contents on device performance including efficiency, hysteresis and stability. This study finds that a moderate residual of PbI2 can deliver stable and high efficiency of solar cells without hysteresis, while too much residual PbI2 will lead to serious hysteresis and poor transit stability. Solar cells with the efficiencies of 21.6% in small size (0.0737 cm2 ) and 20.1% in large size (1 cm2 ) with moderate residual PbI2 in perovskite layer are obtained. The certificated efficiency for small size shows the efficiency of 20.9%, which is the highest efficiency ever recorded in planar-structure perovskite solar cells, showing the planar-structure perovskite solar cells are very promising.

Synthesis of Large-Sized Single-Crystal Hexagonal Boron Nitride Domains on Nickel Foils by Ion Beam Sputtering Deposition

Large-sized single-crystal h-BN domains with a lateral size up to 100 μm are synthesized on Ni foils by ion-beam sputtering deposition. The nucleation density of h-BN is dramatically decreased by reducing the concentrations of both active sites and species on the Ni surface through a brief in situ pretreatment of the substrate and optimization of the growth parameters, enabling the growth of large-sized domains.

DIAMOND FILMS AS SUBSTRATES FOR GLUCOSE SENSORS

Abstract A new diamond-film-based microminiaturized glucose sensor was fabricated. The linear range of the sensor increased to a glucose concentration of 12 mM/l and the sensitivity was 58.8 nA/mM/l. The processing technology was simplified because the Ti interlayer was not necessary due to good adhesion of microelectrodes to diamond film.

Formation and local conduction of nanopits in BiFeO3 epitaxial films

The creation and manipulation of one-dimensional conducting channels, V-shaped nanopits, in otherwise insulating BiFeO3 epilayers are reported. The formation and thickness-dependent evolution of nanopits have a close correlation with the relaxation of shear strain that stems from the crystal symmetry mismatch between BiFeO3 and the substrate. The local conduction at the nanopits exhibits a rectification behavior, and is governed by interface-regulated Poole–Frenkel emission. The accumulation of oxygen vacancies near the nanopits not only modifies the interface barrier height, but also delivers donor states in the vicinity of the conduction band edge, and therefore leads to locally enhanced nanopit conductance. Our findings provide a new insight into the interplay between defects and epitaxial strain, and open up a possible avenue for oxide nanoelectronics.

Structural, electrical, and optical properties of InAsxSb1−x epitaxial films grown by liquid-phase epitaxy

The InAsxSb1-x films were grown on (100) GaSb substrates by liquid-phase epitaxy, and their structural, electrical, and optical properties were investigated. The high-resolution x-ray diffraction results reveal that the single crystalline InAsxSb1-x films with a midrange composition are epitaxially grown on the GaSb substrates. Temperature dependence of the Hall mobility was theoretically modeled by considering several predominant scattering mechanisms. The results indicate that ionized impurity and dislocation scatterings dominate at low temperatures, while polar optical phonon scattering is important at room temperature (RT). Furthermore, the InAsxSb1-x films with the higher As composition exhibit the better crystalline quality and the higher mobility. The InAs0.35Sb0.65 film exhibits a Hall mobility of 4.62x10(4) cm(2) V-1 s(-1). The cutoff wavelength of photoresponse is extended to about 12 mu m with a maximum responsivity of 0.21 V/W at RT, showing great potential for RT long-wavelength infrared detection

Thermal test and analysis of concentrator solar cells

Under high concentration the temperature of photovoltaic solar cells is very high. It is well known that the efficiency and performance of photovoltaic solar cells decrease with the increase of temperature. So cooling is indispensable for a concentrator photovoltaic solar cell at high concentration. Usually passive cooling is widely considered in a concentrator system. However, the thermal conduction principle of concentrator solar cells under passive cooling is seldom reported. In this paper, GaInP/GaAs/Ge triple junction solar cells were fabricated using metal organic chemical vapor deposition technique. The thermal conductivity performance of monolithic concentrator GaInP/GaAs/Ge cascade solar cells under 400X concentration with a heat sink were studied by testing the surface and backside temperatures of solar cells. The tested result shows that temperature difference between both sides of the solar cells is about 1K. A theoretical model of the thermal conductivity and thermal resistance of the GaInP/GaAs/Ge triple junction solar cells was built, and the calculation temperature difference between both sides of the solar cells is about 0.724K which is consistent with the result of practical test. Combining the theoretical model and the practical testing with the upper surface temperature of tested 310K, the temperature distribution of the solar cells was researched.

Reliable concentrated photovoltaic system with compound concentrator

Concentrated photovoltaic systems (CPVSs) draw more and more attention because of high photovoltaic conversion efficiency, low consumption of solar cell, and low cost of power generation. However, the fallibility of the tracker in such systems has hindered their practical application for more than twenty years. The tracker is indispensable for a CPVS since only normal-incident sunlight can be focused on the solar cell chips, even a slight deviation of incident light will result in a significant loss of solar radiation, and hence a distinct decrease in electricity output. Generally, the more accurate the tracker is, the more reliable the system is. However, it is not exactly the case for a CPVS reliability, because the more accurate the tracker is, the better environment it demands. A CPVS is usually has to subjected to harsh environmental conditions, such as strong wind, heavy rain or snow, and huge changes of temperature, which leads to the invalidation of the systems high-accuracy tracker. Hence, the reliability of a CPVS cannot be improved only by enhancing the trackers accuracy. In this paper, a novel compound concentrator, combination of Fresnel lens and photo-funnel, has been adopted in a prototype CPVS. Test results show that the compound concentrator can relax the angle tolerance from one tenth to five degrees of arc at 400 suns, which can help a CPVS endure serious environment and remain its reliability over long period. The CPVS with compound concentrator is attractive for commercial application.