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The roles of bulk surface states and interfacial defects are probed experimentally using a combination of current-voltage, capacitance-voltage, and impedance measurements. The critical importance of the quality of both the film and interfaces is evident in current-voltage measurements where shunting and interface states result in large dark currents and the subsequent loss of J. These properties are shown to be critically related to the nature and role of the PbS QD interface with the (nominally) ohmic gold contact. Specifically, the nonideality of this interface results in the formation of an electric field and therefore a Schottky barrier that opposes the transport of carriers across the conventional ZnO-PbS CQD system. Nonidealities in the structure and absorber layer are also reflected in nonmonotonic behavior and dispersion in C-V measurements with trapping processes on the CQD surfaces, and the ZnO/PbS and PbS/Au interfaces also affecting the carrier dynamics, which is reflected in the response time of these systems under different biases.

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This article proposed a two-phase design scheme of Stephenson six-bar working mechanisms for servo mechanical presses with high mechanical advantage. In the qualitative design phase, first, a Stephenson six-bar mechanism with a slide was derived from Stephenson six-bar kinematic chains. Second, based on the instant center analysis method, the relationship between mechanical advantage and some special instant centers was founded, and accordingly a primary mechanism configuration with high mechanical advantage was designed qualitatively. Then, a parameterized prototype model was established, and the influences of design parameters toward slide kinematical characteristics were analyzed. In the quantitative design phase, a multi-objective optimization model, aiming at high mechanical advantage and dwelling characteristics, was built, and a case design was done to find optimal dimensions. Finally, simulations based on the software ADAMS were conducted to compare the transmission characteristics of the optimized working mechanism with that of slide-crank mechanism and symmetrical toggle mechanism, and an experimental press was made to validate the design scheme. The simulation and experiment results show that, compared with general working mechanisms, the Stephenson six-bar working mechanism has higher mechanical advantage and better dwelling characteristics, reducing capacities and costs of servo motors effectively.