A low-bandgap dimeric porphyrin molecule for 10% efficiency solar cells with small photon energy loss

Dimeric porphyrin molecules have great potential as donor materials for high performance bulk heterojunction organic solar cells (OSCs). Recently reported dimeric porphyrins bridged by ethynylenes showed power conversion efficiencies (PCEs) of more than 8%. In this study, we design and synthesize a new conjugated dimeric D-A porphyrin ZnP2BT-RH, in which the two porphyrin units are linked by an electron accepting benzothiadiazole (BT) unit. The introduction of the BT unit enhances the electron delocalization, resulting in a lower highest occupied molecular orbital (HOMO) energy level and an increased molar extinction coefficient in the near-infrared (NIR) region. The bulk heterojunction solar cells with ZnP2BT-RH as the donor material exhibit a high PCE of up to 10% with a low energy loss (Eloss) of only 0.56 eV. The 10% PCE is the highest for porphyrin-based OSCs with a conventional structure, and this Eloss is also the smallest among those reported for small molecule-based OSCs with a PCE higher than 10% to date

In Situ Structure Characterization in Slot-Die-Printed All-Polymer Solar Cells with Efficiency Over 9%

Herein, high-performance printed all-polymer solar cells (all-PSCs) based on a bulk-heterojunction (BHJ) blend film are demonstrated using PTzBI as the donor and N2200 as the acceptor. A slot-die process is used to prepare the BHJ blend, which is a cost-effective, high-throughput approach to achieve large-area photovoltaic devices. The real-time crystallization of polymers in the film drying process is investigated by in situ grazing incidence wide-angle X-ray scattering characterization. Printing is found to significantly improve the crystallinity of the polymer blend in comparison with spin coating. Moreover, printing with 1,8-diiodooctane as the solvent additive enhances the polymer aggregation and crystallization during solvent evaporation, eventually leading to multi-length-scale phase separation, with PTzBI-rich domains in-between the N2200 crystalline fibers. This unique morphology achieved by printing fabrication results in an impressively high power conversion efficiency of 9.10%, which is the highest efficiency reported for printed all-PSCs. These findings provide important guidelines for controlling film drying dynamics for processing all-PSCs

Characterization of Pt-Si interface by spectroscopic ellipsometry

Spectroscopic ellipsometric measurements for Pt/n-Si samples with different thickness of Pt films have been performed. The thickness of the Pt films determined with the three-phase model (air/Pt/Si) changes with the wavelength λ while that with the four-phase model (air/Pt/interface layer/Si) remains unchanged, showing the existence of an interface layer. At the same time, the apparent optical dielectric constants of the interface layer as a function of λ are also obtained. A calculation based on the effective medium theory is carried out to simulate the optical dielectric data of the interface layer. Some structural information of the interface layer is obtained from the calculation. © 1994 American Institute of Physics.published_or_final_versio

Temperature dependence of current transport in Al/Al 2O 3 nanocomposite thin films

In this work, Al/Al 2O 3 nanocomposite thin film is deposited on Si substrate by radio frequency sputtering to form a metal-insulator-semiconductor structure. It is found that the current conduction at low fields is greatly enhanced with temperature. The current increase can be attributed to the decrease in the tunneling resistance and/or the formation of some tunneling paths due to the release of some measurement-induced charges trapped in the thin film as a result of increase in the temperature. The current conduction evolves with a trend toward a three-dimensional transport as the temperature increases. © 2011 American Institute of Physics.published_or_final_versio

Influence of nitrogen on tunneling barrier heights and effective masses of electrons and holes at lightly-nitrided SiO2/Si interface

We have determined both the effective masses and the barrier heights for electrons and holes in pure SiO2 and lightly nitrided oxides with various nitrogen concentrations up to 4.5 at %. In contrast to previous studies which were usually carried out by assuming a value for either the effective mass or the barrier height, this study does not make such an assumption. The approach is proven to be reliable by examining the result for the well-studied pure SiO2 thin films. It is observed that with the increase of the nitrogen concentration the effective masses increase while both the barrier heights and the energy gap decrease. © 2004 American Institute of Physics.published_or_final_versio

Two-terminal write-once-read-many-times memory device based on charging-controlled current modulation in Al/Al-Rich Al 2O 3/p-Si diode

A write-once-read-many-times (WORM) memory device was realized based on the charging-controlled modulation in the current conduction of Al/Al-rich Al 2O 3/p-type Si diode. A large increase in the reverse current of the diode could be achieved with a negative charging voltage, e.g., charging at -25 V for 1 ms results in a current increase by about four orders. Memory states of the WORM device could be altered by changing the current conduction with charge trapping in the Al-rich Al 2O 3 layer. The memory exhibited good reading endurance and retention characteristics. © 2011 IEEE.published_or_final_versio

Interferon-gamma inducible protein 10 (IP10) induced cisplatin resistance of HCC after liver transplantation through ER stress signaling pathway.

Tumor recurrence remains an obstacle after liver surgery, especially in living donor liver transplantation (LDLT) for patients with hepatocellular carcinoma (HCC). The acute-phase liver graft injury might potentially induce poor response to chemotherapy in recurrent HCC after liver transplantation. We here intended to explore the mechanism and to identify a therapeutic target to overcome such chemoresistance. The associations among graft injury, overexpression of IP10 and multidrug resistant genes were investigated in a rat liver transplantation model, and further validated in clinical cohort. The role of IP10 on HCC cell proliferation and tumor growth under chemotherapy was studied both in vitro and in vivo. The underlying mechanism was revealed by detecting the activation of endoplasmic reticulum (ER) stress signaling pathways. Moreover, the effect of IP10 neutralizing antibody sensitizing cisplatin treatment was further explored. In rat liver transplantation model, significant up-regulation of IP10 associated with multidrug resistant genes was found in small-for-size liver graft. Clinically, high expression of circulating IP10 was significant correlated with tumor recurrence in HCC patients underwent LDLT. Overexpression of IP10 promoted HCC cell proliferation and tumor growth under cisplatin treatment by activation of ATF6/Grp78 signaling. IP10 neutralizing antibody sensitized cisplatin treatment in nude mice. The overexpression of IP10, which induced by liver graft injury, may lead to cisplatin resistance via ATF6/Grp78 ER stress signaling pathway. IP10 neutralizing antibody could be a potential adjuvant therapy to sensitize cisplatin treatment

Interfacial Fermi level and surface band bending in Ni/semi-insulating GaAs contact

For nickel on the chemically clean surface of undoped semi-insulating GaAs at room temperature, an upward surface band bending of 0.062 eV and a barrier height of 0.690 eV have been observed by the photovoltage and the internal photoemission techniques, respectively. The observed surface band bending is in excellent agreement with its predicted value, and the observed barrier height also agrees very well with its value from the very careful analysis of reversed I-V data. It has been determined that the interfacial Fermi level lies at 0.690 eV below the GaAs conduction band minimum at the interface. The interfacial Fermi level is found to coincide with the energy level of the EL2 native defect, indicating the importance of the EL2 in the Fermi level pinning at the interface. © 1995 American Institute of Physics.published_or_final_versio

Barrier height change in very thin SiO2 films caused by charge injection

In this paper, we report an investigation of barrier height change in gate oxide caused by charge injection. By analyzing the small change in the post-stress Fowler-Nordheim (FN) tunneling current through the oxide layer, the change of the oxide barrier height due to charge injection is determined quantitatively. The barrier height changes associated with different charge-injection directions and measurement polarities for n-channel metal oxide semiconductor field-effect transistors (MOSFETs) are presented. For comparison a measurement on a p-channel MOSFET is also carried out. For all the cases, the barrier height changes always exhibit a power law dependence on injected charge.published_or_final_versio