Xinqian Zhang

Active-layer evolution and efficiency improvement of (CH3NH33Bi2I9-based solar cell on TiO2-deposited ITO substrate

We systematically investigated the development of film morphology and crystallinity of methyl-ammonium bismuth (III) iodide (MA3Bi2I9) through onestep spin-coating on TiO2-deposited indium tin oxide (ITO)/glass. The precursor solution concentration and substrate structure have been demonstrated to be critically important in the active-layer evolution of the MA3Bi2I9-based solar cell. This work successfully improved the cell efficiency to 0.42% (average: 0.38%) with the mesoscopic architecture of ITO/compact-TiO2/mesoscopic-TiO2 (meso-TiO2)/MA3Bi2I9/2,2′,7,7′-tetrakis(N,N-di-4-methoxyphenylamino)-9,9′spiro-bifluorene (spiro-MeOTAD)/MoO3/Ag under a precursor concentration of 0.45 M, which provided the probability of further improving the efficiency of the Bi3+-based lead-free organic–inorganic hybrid solar cells.

Thiocyanate assisted performance enhancement of formamidinium based planar perovskite solar cells through a single one-step solution process

Thiocyanate ammonium (NH4SCN) is introduced into the fabrication of formamidinium lead triiodide (FAPbI3) films through one-step spin-coating. The promoted formation of black trigonal phase α-FAPbI3 with better crystallinity has been observed after the addition of NH4SCN, together with the supression of the formation of yellow hexagonal phase δ-FAPbI3. Planar perovskite solar cells (PVSCs) based on NH4SCN-assisted formed α-FAPbI3 films with high quality present a highest power conversion efficiency of 11.44% when 30 mol% NH4SCN is applied. Notably, the addition of NH4SCN is found to enhance the moisture stability of the perovskite. As a result, the planar PVSCs with 30 mol% NH4SCN additive show improved stability under ambient conditions (RH: 30–40%) over those based on pristine FAPbI3. NH4SCN simultaneously enhances the efficiency and moisture stability of FAPbI3 based PVSCs through a single one-step solution method, facilitating their commercial fabrication and application.

Vertically Oriented 2D Layered Perovskite Solar Cells with Enhanced Efficiency and Good Stability

Vertically oriented highly crystalline 2D layered (BA)2 (MA)n-1 Pbn I3n+1 (BA = CH3 (CH2 )3 NH3 , MA = CH3 NH3 , n = 3, 4) perovskite thin-films are fabricated with the aid of ammonium thiocyanate (NH4 SCN) additive through one-step spin-coating process. The humidity-stability of the film is certified by the almost unchanged X-ray diffraction patterns after exposed to humid atmosphere (Hr = 55 ± 5%) for 40 d. The photovoltaic devices with the structure of indium tin oxide(ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate)/(BA)2 (MA)n-1 Pbn I3n+1 (n = 3,4)/[6,6]-phenyl-C61 -butyric acid methyl ester/Bathocuproine/Ag are fabricated. The devices based on (BA)2 (MA)2 Pb3 I10 perovskite (n = 3) with the precursor composition of BAI:methylammonium iodide:PbI2 :NH4 SCN = 2:2:3:1 (by molar ratio) show an averaged power conversion efficiency (PCE) of 6.82%. In the case of (BA)2 (MA)3 Pb4 I13 (n = 4), a higher PCE of 8.79% is achieved. Both of the unsealed devices perform unique stability with almost unchanged PCE during the period of storage in purified N2 glove box. This work provides a simple and effective method to enhance the efficiency of the 2D perovskite solar cell.

Effect of microstructure on the properties of Zr–Mn–V–Ni AB2 type hydride electrode alloys

The effect of the microstructure for multicomponent ZrMn0.9-xVxNi1.1 (x = 0.1-0.8) hydride electrode alloys on their hydrogen absorbing capacity, activation and high rate discharge capacity was investigated. The electrochemical properties and microstructure changed with the alloys compositions. The microstructure were determined by the combination of transmission electron microscopy (TEM) and X-ray Rietveld analysis. Hexagonal C14 type, cubic C15 type Laves phase and tetragonal body centered Zr9Ni11 coexisted in the alloys of given compositions. The metastable Zr9Ni11 phase was stabilized at room temperature as long range ordered state along [100] and [010] directions. Substructure of each phase and the orientation relations among the existing phases were investigated in detail. Stacking faults in the C15 Laves phase and precipitation of Zr-Ni binaries considerably enhanced the activation and high rate discharge capacity of Laves phase

Highly oriented two-dimensional formamidinium lead iodide perovskites with a small bandgap of 1.51 eV

Due to the quantum confinement effects, the bandgap of two-dimensional (2D) perovskites increases when the thickness of the inorganic slabs decreases. This could result in insufficient light absorption that limits the overall performance of perovskite solar cells. Here we report a series of small bandgap 2D perovskites using mixed butylammonium (BA) and formamidinium (FA) cations, i.e. (BA)2(FA)n−1PbnI3n+1 (n = 1–5). In particular, 2D perovskite (BA)2(FA)2Pb3I10 shows a small bandgap of 1.51 eV, which is comparable to state-of-the-art three-dimensional perovskites. A strongly preferential out-of-plane crystallographic alignment of the inorganic perovskite component in the (BA)2(FA)2Pb3I10 film is achieved by the addition of thiourea in the precursor. This significantly improves charge transport and thus leads to highly efficient inverted solar cells with a planar structure of ITO/PEDOT:PSS/(BA)2(FA)2Pb3I10/PC61BM/BCP/Ag. With the best power conversion efficiency of 6.88%, we demonstrated the highest PCE reported for FA based low-n (n < 4) 2D perovskite solar cells. By virtue of the stable 2D perovskites, the unencapsulated device retains 80% efficiency after storing in air with a humidity of 25 ± 5% for 25 days, indicating excellent stability against moisture and oxygen.

Effect of nanometer-sized WC additive on the electrochemical behaviors of AB2 – type hydrogen storage alloy

Abstract The nanometer-sized WC powders were evidently found to catalytically decompose the molecular water and chemical-adsorb hydrogen atoms in alkaline solution. The WC additive also accelerated the combination reaction of hydrogen in the hydride electrode during cathodic polarization (charging), inducing rapid H 2 emission. Electrochemical impedance analysis (EIS) showed that the hydrogen atoms adsorbed on the surface of WC powders were first electrochemically oxidized due to their lower chemical bonding, and that the low conductivity of WC powder increased the internal resistance of hydride electrodes.

TEM investigation of ZrO2 in Zr(Ni0.55VxMn0.45-x)2 hydrogen storage alloys

Zirconia particles were found in AB(2) type Zr(Ni0.55VxMn0.45-x)(2), x=0.05-0.4, hydrogen storage alloys and studied with TEM. Results showed the high temperature tetragonal phase (T) of zirconia coexisted with a monoclinic (M) one at the room temperature. This can be attributed to the shape effect and volume restraint in the T-M transition. The orientation relationship between T and M phases, the morphology and structural aspects of fully transformed M-phase as well as its influence on activation of the alloys were also discussed