Chu-Hsuan Lin

Effect of non-lattice oxygen on ZrO2-based resistive switching memory.

ZrO2-based resistive switching memory has attracted much attention according to its possible application in the next-generation nonvolatile memory. The Al/ZrO2/Pt resistive switching memory with bipolar resistive switching behavior is revealed in this work. The thickness of the ZrO2 film is only 20 nm. The device yield improved by the non-lattice oxygen existing in the ZrO2 film deposited at room temperature is firstly proposed. The stable resistive switching behavior and the long retention time with a large current ratio are also observed. Furthermore, it is demonstrated that the resistive switching mechanism agrees with the formation and rupture of a conductive filament in the ZrO2 film. In addition, the Al/ZrO2/Pt resistive switching memory is also possible for application in flexible electronic equipment because it can be fully fabricated at room temperature.

Influence of graphene oxide on metal-insulator-semiconductor tunneling diodes.

In recent years, graphene studies have increased rapidly. Graphene oxide, which is an intermediate product to form graphene, is insulating, and it should be thermally reduced to be electrically conductive. We herein describe an attempt to make use of the insulating properties of graphene oxide. The graphene oxide layers are deposited onto Si substrates, and a metal-insulator-semiconductor tunneling structure is formed and its optoelectronic properties are studied. The accumulation dark current and inversion photocurrent of the graphene oxide device are superior to the control device. The introduction of graphene oxide improves the rectifying characteristic of the diode and enhances its responsivity as a photodetector. At 2 V, the photo-to-dark current ratio of the graphene oxide device is 24, larger than the value of 15 measured in the control device.

Efficiency Improvement of HIT Solar Cells on p-Type Si Wafers

Single crystal silicon solar cells are still predominant in the market due to the abundance of silicon on earth and their acceptable efficiency. Different solar-cell structures of single crystalline Si have been investigated to boost efficiency; the heterojunction with intrinsic thin layer (HIT) structure is currently the leading technology. The record efficiency values of state-of-the art HIT solar cells have always been based on n-type single-crystalline Si wafers. Improving the efficiency of cells based on p-type single-crystalline Si wafers could provide broader options for the development of HIT solar cells. In this study, we varied the thickness of intrinsic hydrogenated amorphous Si layer to improve the efficiency of HIT solar cells on p-type Si wafers.

Passivation ability of graphene oxide demonstrated by two-different-metal solar cells

The study on graphene oxide (GO) grows rapidly in recent years. We find that graphene oxide could act as the passivation material in photovoltaic applications. Graphene oxide has been applied on Si two-different-metal solar cells. The suitable introduction of graphene oxide could result in obvious enhancement on the efficiency. The simple chemical process to deposit graphene oxide makes low thermal budget, large-area deposition, and fast production of surface passivation possible. The different procedures to incorporate graphene oxide in Si two-different-metal solar cells are compared, and 21% enhancement on the efficiency is possible with a suitable deposition method.

Three-Terminal Amorphous Silicon Solar Cells

Many defects exist within amorphous silicon since it is not crystalline. This provides recombination centers, thus reducing the efficiency of a typical a-Si solar cell. A new structure is presented in this paper: a three-terminal a-Si solar cell. The new back-to-back p-i-n/n-i-p structure increased the average electric field in a solar cell. A typical a-Si p-i-n solar cell was also simulated for comparison using the same thickness and material parameters. The 0.28 μm-thick three-terminal a-Si solar cell achieved an efficiency of 11.4%, while the efficiency of a typical a-Si p-i-n solar cell was 9.0%. Furthermore, an efficiency of 11.7% was achieved by thickness optimization of the three-terminal solar cell.

Antireflection with graphene oxide

Graphene oxide (GO) obtained by chemical exfoliation exhibits a quasi-2D structure. Its refractive index is very close to the theoretically predicted best refractive index for a single antireflection coating layer between air and Si. The robust honeycomb plane structure of GO makes it a promising mask candidate for surface texturizing. Here, we demonstrate different GO distributions on Si, and report the reflection properties before and after etching. For an etched Si substrate with suitable GO coating, the reflectance reached 2.1% at 667 nm. Preliminary 1.5-min-long etching of a p+nn+ solar cell with a GO mask boosted the efficiency from 7.09% to 7.55%.

Single Grain Boundary Modeling and Design of Microcrystalline Si Solar Cells

For photovoltaic applications, microcrystalline silicon has a lot of advantages, such as the ability to absorb the near-infrared part of the solar spectrum. However, there are many dangling bonds at the grain boundary in microcrystalline Si. These dangling bonds would lead to the recombination of photo-generated carriers and decrease the conversion efficiency. Therefore, we included the grain boundary in the numerical study in order to simulate a microcrystalline Si solar cell accurately, designing new three-terminal microcrystalline Si solar cells. The 3-μm-thick three-terminal cell achieved a conversion efficiency of 10.8%, while the efficiency of a typical two-terminal cell is 9.7%. The three-terminal structure increased the JSC but decreased the VOC, and such phenomena are discussed. High-efficiency and low-cost Si-based thin film solar cells can now be designed based on the information provided in this paper.

Gold-Nanoparticle-Coated Ge MIS Photodiodes

Ge photodiodes with ultra-high responsivities have been demonstrated with gold nanoparticle assistance. The responsivity can reach a value of 37.7 A/W, which corresponds to a gain of 76. Such a high responsivity originates from the amassment of photo-generated holes in Ge under the boundary of gold nanoparticles, which reduces the barrier for electron tunneling from metal to the hole-amassment Ge ring areas. The depletion layer thinning due to hole amassment is not only proved by band diagram simulation but also confirmed by capacitance measurement.

Bipolar resistive switching in Al/ZrO 2 /Pt device fabricated at room temperature

ZrO2-based resistive random access memory possessing stable resistive switching is investigated in this work. The bipolar resistive switching found in Al/ZrO2/Pt device shows more promising for application due to its distinguishable switching voltages. Furthermore, good endurance and retention time with a large resistive ratio are also observed in the device. All the fabricating steps of the device were carried out at room temperature, and it is possible for application in flexible electronic equipments.

Graphene oxide for metal-insulator-semiconductor tunneling diodes

In this study, we have inserted the graphene oxide (GO) in the metal/insulator/semiconductor tunneling diodes. The graphene oxide devices reveal the better stability as compared with the control devices. At a small positive bias, different control devices have different magnitude of photocurrents, while photocurrents of GO devices have close magnitude. At 2 V, the photocurrent density of the GO device have a minimum value of 2.7×10-3 A/cm2, while the control device can only reach a maximum value of 1.4×10-3 A/cm2. The simple GO process can obviously improve the characteristics of metal/insulator/semiconductor tunneling diodes