Search

In this work, we report a solution processed hole extraction layer (HEL) for highly efficient organic solar cells (OSCs), which is formed by CuSCN and perylene. It shows that the introduction of perylene helps to polish the interface between HEL and active layers, leading to efficient charge transport and collection, diminished recombination loss, and thereby improving the photovoltaic performance. In poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2- b ; 4,5- b ′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4- b ]thiophene-)-2-carboxylate-2-6-diyl)]:[6,6]-phenyl C 71 -butyric acid methyl ester (PTB7-Th:PC 71 BM) based OSCs, over 9% enhancement of power conversion efficiency (PCE) is obtained in the cells using bilayer CuSCN/perylene as HEL compared with that of the reference cell using pure CuSCN as HEL. The advantage of bilayer CuSCN/perylene HEL is also confirmed in nonfullerene system. An improved PCE is also obtained after application of perylene in nonfullerene system based cell. Furthermore, superior air stability has been observed in CuSCN and CuSCN/perylene HEL based cells. The use of a bilayer CuSCN/perylene HEL proves a potential approach to obtain efficient and stable OSCs. Image 1 • Solution processed hole extraction layer (HEL) is formed by perylene and CuSCN. • Over 9% improvement of PCE is obtained in PTB7-Th:PC 71 BM based cells. • Perylene helps to polish interface contact between HEL and active layers. • Perylene favors charge extraction as charge transfer mediator. • The novel HEL diminishes recombination loss, and promotes photons utilization. [ABSTRACT FROM AUTHOR]

LiNi0.5Co0.2Mn0.3O2 is redesigned into a new core-shelled Li[(Ni0.8Co0.1Mn0.1)2/7]core[(Ni1/3Co1/3Mn1/3)3/14]inner-shell[(Ni0.4Co0.2Mn0.4)1/2]outer-shellO2, in which LiNi0.8Co0.1Mn0.1O2 may deliver high capacity and LiNi0.4Co0.2Mn0.4O2 provides structural and thermal stability. To achieve such designed structure, double-shelled hydroxide precursors are firstly prepared via a co-precipitation route. Scanning electron microscope (SEM) shows that all precursors are of 6–10 μm spherical secondary particles developed from nanosheet-shaped primary particles. Energy disperse X-ray spectrum (EDS) on the surface of precursors, in combination with increase of particles size from core to shell during co-precipitation process, confirms the formation of core–shell structure as designed. The spherical morphology is preserved after lithiation at different temperatures from 800 °C to 900 °C while the morphology of primary particles changes from nano-sized plate to micron-sized rectangular-like shapes. EDS surface composition analysis of lithiated compounds also strongly suggests the formation of core–shell structure; nevertheless, diffusion of transition metal ions between the core and shell occurs and becomes severe with increase of sintering temperature. Consequently, the double-shelled materials especially prepared at 850 °C display the remarkably improved cycleability, rate capability, and thermal stability in contrast to normal one. The enhancement of those properties may be ascribed to structurally stable double shell components, especially outer shell. [ABSTRACT FROM AUTHOR]

Abstract: Prospective positive-electrode (cathode) materials for a lithium secondary battery, viz., Li[Li0.2Ni0.2−x/2Mn0.6−x/2Cr x ]O2 (x =0, 0.02, 0.04, 0.06, 0.08), were synthesized using a solid-state pyrolysis method. The structural and electrochemical properties were examined by means of X-ray diffraction, cyclic voltammetry, SEM and charge–discharge tests. The results demonstrated that the powders maintain the α-NaFeO2-type layered structure regardless of the chromium content in the range x ≤0.08. The Cr doping of x =0.04 showed improved capacity and rate capability comparing to undoped Li[Li0.2Ni0.2Mn0.6]O2. ac impedance measurement showed that Cr-doped electrode has the lower impedance value during cycling. It is considered that the higher capacity and superior rate capability of Cr-doping samples would be ascribed to the reduced resistance of the electrode during cycling. [Copyright &y& Elsevier]

Abstract: The layered Li[Ni(1−x)/3Mn(1−x)/3Co(1−x)/3Mo x ]O2 cathode materials (x =0, 0.005, 0.01, and 0.02) were prepared by a solid-state pyrolysis method (700, 800, 850, and 900°C). Its structure and electrochemical properties were characterized by XRD, SEM, XPS, cyclic voltammetry, and charge/discharge tests. It can be learned that the doped sample of x =0.01 calcined at 800°C shows the highest first discharge capacity of 221.6mAhg−1 at a current density of 20mAg−1 in the voltage range of 2.3–4.6V, and the Mo-doped samples exhibit higher discharge capacity and better cycle-ability than the undoped one at room temperature. [Copyright &y& Elsevier]