The carrier dynamics in organic photovoltaic (OPV) cells were investigated by impedance spectroscopy. We introduced a novel impedance spectrum representation called dynamic modulus plot (DMP), which allowed us to observe the layer-to-layer carrier injection behavior graphically. In this work, the impedance responses were characterized in the N,N'-diphenyl-N,N'-di-m-tolyl-4,4'-diaminobiphenyl (TPD)/C 60 p-n heterostructured OPV cells against applied voltages. The dependence of impedance responses on the layer thickness revealed a constant internal electric field that disturbed the carrier transport within the OPV cells. We applied this technique to new donor materials, in which thiophene units were inserted to the center of TPD. By increasing the number of thiophene units in TPD the fill-factor (FF) improved from 33% to 59%, which increased the power conversion efficiency (PCE). Based on the DMP analysis, we assigned the improvement in device performance to the reduction of the internal electric field.

No abstract

No abstract

A thin-film structure comprising Al 2 O 3 /Al-rich Al 2 O 3 /SiO 2 was fabricated on Si substrate. We used radio-frequency magnetron co-sputtering with Al metal plates set on an Al 2 O 3 target to fabricate the Al-rich Al 2 O 3 thin film, which is used as a charge storage layer for nonvolatile Al 2 O 3 memory. We investigated the charge trapping characteristics of the film. When the applied voltage between the gate and the substrate is increased, the hysteresis window of capacitance-voltage (C-V) characteristics becomes larger, which is caused by the charge trapping in the film. , which is 2.6 times larger than that of the trap memory using SiN as the charge storage layer. The device structure would be promising for lowcost nonvolatile memory.

No abstract