Effects of drying time on the formation of merged and soft MAPbI3 grains and their photovoltaic responses.

The grain sizes of soft CH3NH3PbI3 (MAPbI3) thin films and the atomic contact strength at the MAPbI3/P3CT-Na interface are manipulated by varying the drying time of the saturated MAPbI3 precursor solutions, which influences the device performance and lifespan of the resultant inverted perovskite photovoltaic cells. The atomic-force microscopy images, cross-sectional scanning electron microscopy images, photoluminescence spectra and absorbance spectra show that the increased short-circuit current density (J SC) and increased fill factor (FF) are mainly due to the formation of merged MAPbI3 grains. Besides, the open-circuit voltage (V OC) of the encapsulated photovoltaic cells largely increases from 1.01 V to 1.15 V, thereby increasing the power conversion efficiency from 17.89% to 19.55% after 30 days, which can be explained as due to the increased carrier density of the MAPbI3 crystalline thin film. It is noted that the use of the optimized drying time during the spin coating process results in the formation of merged MAPbI3 grains while keeping the contact quality at the MAPbI3/P3CT-Na interface, which boosts the device performance and lifespan of the resultant perovskite photovoltaic cells.

Understanding the PEDOT:PSS, PTAA and P3CT-X Hole-Transport-Layer-Based Inverted Perovskite Solar Cells.

The power conversion efficiencies (PCEs) of metal-oxide-based regular perovskite solar cells have been higher than 25% for more than 2 years. Up to now, the PCEs of polymer-based inverted perovskite solar cells are widely lower than 23%. PEDOT:PSS thin films, modified PTAA thin films and P3CT thin films are widely used as the hole transport layer or hole modification layer of the highlyefficient inverted perovskite solar cells. Compared with regular perovskite solar cells, polymer-based inverted perovskite solar cells can be fabricated under relatively low temperatures. However, the intrinsic characteristics of carrier transportation in the two types of solar cells are different, which limits the photovoltaic performance of inverted perovskite solar cells. Thanks to the low activation energies for the formation of high-quality perovskite crystalline thin films, it is possible to manipulate the optoelectronic properties by controlling the crystal orientation with the different polymer-modified ITO/glass substrates. To achieve the higher PCE, the effects of polymer-modified ITO/glass substrates on the optoelectronic properties and the formation of perovskite crystalline thin films have to be completely understood simultaneously.

Stable and efficient soft perovskite crystalline film based solar cells prepared with a facile encapsulation method.

The quasi Fermi level for electrons in a soft perovskite crystalline thin film and the contact qualities at the PCBM/perovskite and perovskite/P3CT-Na interfaces can be increased using a facile encapsulation method, which improves the device performance and stability of the resultant perovskite solar cells. In the encapsulated perovskite solar cells, the averaged open-circuit voltage (VOC) largely increases from 0.981 V to 1.090 V after 9 days mainly due to the increased quasi Fermi levels. Besides, the reflectance and photoluminescence (PL) spectra show improved contact qualities at the PCBM/perovskite and perovskite/P3CT-Na interfaces, which can be used to explain the increase in the short-circuit current density (JSC) from 21.68 mA cm-2 to 23.48 mA cm-2 after the encapsulation process. Besides, nanosecond time-resolved PL and temperature-dependent PL spectra can be used to explain the increased VOC, which is mainly due to the increased shallow defect density and thereby increasing the exciton binding energy of the encapsulated perovskite sample. It is noted that the averaged power conversion efficiency (PCE) slowly decreases from 18.24% to 16.52% within 45 days.

19% Efficient P3CT-Na Based MAPbI3 Solar Cells with a Simple Double-Filtering Process.

A high-efficiency inverted-type CH3NH3PbI3 (MAPbI3) solar cell was fabricated by using a ultrathin poly[3-(4-carboxybutyl)thiophene-2,5-diyl]-Na (P3CT-Na) film as the hole transport layer. The averaged power conversion efficiency (PCE) can be largely increased from 11.72 to 18.92% with a double-filtering process of the P3CT-Na solution mainly due to the increase in short-circuit current density (JSC) from 19.43 to 23.88 mA/cm2, which means that the molecular packing structure of P3CT-Na thin film can influence the formation of the MAPbI3 thin film and the contact quality at the MAPbI3/P3CT-Na interface. Zeta potentials, atomic-force microscopic images, absorbance spectra, photoluminescence spectra, X-ray diffraction patterns, and Raman scattering spectra are used to understand the improvement in the JSC. Besides, the light intensity-dependent and wavelength-dependent photovoltaic performance of the MAPbI3 solar cells shows that the P3CT-Na thin film is not only used as the hole transport layer but also plays an important role during the formation of a high-quality MAPbI3 thin film. It is noted that the PCE values of the best P3CT-Na based MAPbI3 solar cell are higher than 30% in the yellow-to-near infrared wavelength range under low light intensities. On the other hand, it is predicted that the double-filtering method can be readily used to increase the PCE of polymer based solar cells.

[Protective effect of ferulic acid on neuronal apoptosis of spinal cord subsequent to aortic blood cross-clamping in rabbits].

OBJECTIVE: To investigate the protective effect of ferulic acid on neuronal apoptosis of the spinal cord after aortic blood cross-clamping and its mechanism in rabbits. METHODS: Twenty-four rabbits were randomly divided into sham operation group, ischemia/reperfusion (I/R) injury group and ferulic acid group. Spinal cord I/R injury model was replicated by clamping blood of the infrarenal aorta for 40 minutes followed reperfusion for 7 days. Ferulic acid 50 mg/kg was injected 15 minutes before aortic clamping in ferulic acid group. The aorta was not clamped in sham operation group. Contents of malondialdehyde (MDA) and superoxide dismutase (SOD) in plasma were assayed at 10 minutes before clamping (C-10), before removal of occlusion (C40), at 60 minutes (R60) and on the 7 th day (R7d) after reperfusion. Apoptosis of neurones of spinal cord and the expressions of Bax and Bcl-2 protein were assayed by immunohistochemical technique. Neurologic function score of hind limb was observed after operation. RESULTS: (1)The activity of MDA after I/R in I/R injury group was increased significantly compared with those before clamping and those in sham operation group (P<0.05 or P<0.01). The activity of MDA in ferulic acid group was significantly higher than that at C-10 (P<0.05), while significantly lower than those in I/R injury group at any time point (P<0.05 or P<0.01), but showed no significant difference compared with sham operation group. Changes in SOD activities were opposite to that of MDA. (2)The expression of Bax protein in I/R injury group was increased significantly (P<0.05), but the expression of Bcl-2 protein was decreased significantly compared with that in sham operation group (P<0.01). In ferulic acid group, the expression of Bax protein was significantly lower than that in I/R injury group and higher than that in sham operation group (P<0.01 and P<0.05), and the expression of Bcl-2 protein was higher than those in I/R injury group and sham operation group (both P<0.01). (3)The index of neuronal apoptosis in I/R injury group was significantly higher than that in sham operation group (P<0.01), and that in ferulic acid group was much lower than that in I/R injury group, but higher than sham operation group (P<0.01 and P<0.05). (4)The degree of paralysis in ferulic acid group was significantly lower than that in I/R injury group, and a higher neurologic score was observed (both P<0.01). CONCLUSION: Ferulic acid can reduce the spinal cord neuronal apoptosis as a result of aortic occlusion in rabbits. The possible mechanism is that it decreases protein expression of Bax, increases that of Bcl-2 and enhances antioxidation.

[Effect of propofol on spinal cord apoptosis associated with aortic cross-clamping in rabbits].

OBJECTIVE: To investigate the effect and mechanism of propofol on the spinal cord apoptosis associated with aortic cross-clamping in rabbits. METHODS: Twenty-four rabbits were randomly divided into sham operation group (A), ischemia/reperfusion group (B) and propofol group (C). In group B and C, the infrarenal aorta was clamped for 40 minutes followed by 7 days reperfusion. Ten minutes before clamping, group C was given propofol 5 mg/kg intravenously and continued at a rate of 20 mg x kg(-1)x h(-1) until unclamping. The aorta was not clamped in group A. The plasma concentrations of malondialdehyde (MDA) and superoxide dismutase (SOD) were determined at 10 minutes before clamping (C-10), before unclamping (C40), at 60 minutes (R60) and on the 7th day (R7 d) unclamping. Apoptotic spinal cord cells and expressions of Bax, Bcl-2 protein were measured by immunohistochemical technique. RESULTS: (1)The concentrations of MDA after ischemia and reperfusion in group B were increased significantly compared with C-10 and those in group A (P<0.05 or P<0.01), which in group C were significantly lower than those in group B (P<0.05), but not in group A. Changes in SOD activity were opposite to those in MDA contents in various groups. (2)The expressions of Bax protein in group B were significantly increased compared with those in group A (P<0.05), while the expression of Bcl-2 protein decreased. In group C, Bax protein expression was markedly lower than those in group B and higher than those in group A (P<0.01 and P<0.05), the expression of Bcl-2 was higher than those in groups B and A (both P<0.01). (3)The number of apoptosis cells in group B was much higher than that in group A, which in group C was much lower than that in group B, but higher than that in group A. (4)The ratio of paralysis in group C was significantly lower than that in group B with a high neurologic score (both P<0.01). CONCLUSION: Propofol can reduce the spinal cord apoptosis associated with aortic cross-clamping in rabbits. The possible mechanism is related to the effect of decreasing Bax expression, increasing Bcl-2 expression, and enhancing antioxidation.

Determination of the median effective dose for motor block of intrathecally administered different concentrations of bupivacaine in younger patients. The influence of solution concentration.

OBJECTIVE: To determine the median effective dose (ED50) for motor block of intrathecally administered different concentrations of bupivacaine in younger patients. METHODS: This study was conducted at the Department of Anesthesiology, The First College of Clinical Medical Science, China Three Gorges University, China, on 40 American Society of Anaesthesiologists (ASA) I-II younger patients (18-40 years) undergoing lower limb surgery. These patients were classified into 2 groups according to a computer-generated random number table (Group A - 0.375% bupivacaine, and Group B - 0.75% bupivacaine). Spinal anesthesia was established by bolus administration of various up-and-down doses of 0.375%, or 0.75% plain bupivacaine. These up-and-down doses were determined by Dixon's up-and-down method. The first patient of each group was given 7.5 mg bupivacaine, and the testing interval was set at 0.75 mg. The dose was up, or down, 0.75 mg increments according to the failure or success of the preceding patient's motor block. The degree of motor block after intrathecal administration of bupivacaine was evaluated by the modified Bromage and Hip motor function score. The ED50 were estimated from the up-down sequences using the method of Dixon and Massey. RESULTS: Our results showed that ED50 for motor block of intrathecal bupivacaine was 8.890 mg in Group A, and 9.998 mg in Group B, and the relative motor blocking potency ratio was 1.12. CONCLUSION: The ED50 for motor block of intrathecally administered bupivacaine with higher concentration was slightly higher than that of a lower concentration.