In order to reduce the power-generating cost of silicon solar cells, it is necessary to achieve a high conversion efficiency using a thinner crystalline silicon (c-Si) substrate. The HIT solar cell is an amorphous silicon (a-Si) /crystalline silicon (c-Si) heterojunction solar cell that makes it possible to realize excellent surface passivation and hence high open circuit voltage (Voc). In addition, its symmetrical structure and a low-temperature fabrication process that is under 200°C provide advantages in reducing thermal and mechanical stresses within the device so that it can easily be applied to thinner solar cells. We fabricated HIT solar cells using thin wafers from 58-98 μm, and achieved a 22.8% conversion efficiency with a HIT solar cell using a 98-μm-thick wafer, and an excellent Voc value of 0.747 V with a HIT solar cell using a 58-μm-thick wafer.

Zinc Oxide (ZnO), II-VI compound semiconductor, is a promising material for ultraviolet (UV) photon sensor applications due to its attractive properties such as good photoconductivity, ease processing at low temperatures and excellent radiation hardness. The rf magnetron sputtering is a suitable deposition technique due to better control over stoichiometry and deposition of uniform film. Studies have shown that the presence of surface defects in ZnO and subsequently their passivation are crucial for enhanced photo-response characteristics, and to obtain the fast response speed. Worldwide efforts are continuing to develop good quality ZnO thin films with novel design structures for realization of an efficient UV photon sensor. In the present work, UV photon sensor is fabricated using a ZnO thin films deposited by rf magnetron sputtering on the corning glass substrate. Photo-response, (Ion/Ioff) of as-grown ZnO film of thickness 100 nm is found to be 3×103 with response time of 90 ms for UV intensity of 140 μW/cm2 (λ = 365 nm). With irradiation on ZnO thin film by pulsed Nd:YAG laser (forth harmonics 266 nm), the sensitivity of the UV sensor is found to enhance. The photo-response increases after laser irradiation to 4x104 with a fast response speed of 35 ms and attributed to the change in surface states and the native defects in the ZnO thin film. Further, enhancement in the ultraviolet (UV) photo-response (8×104) of detector was observed after integrating the nano-scale islands of Sn metal on the surface of laser irradiated ZnO thin film.

We report a novel method to selectively deposit materials from solution into imprinted micro-capillaries. Dewetting of the solvent just outside the capillaries is balanced to evaporation inside the capillaries. In this way conductive μ-wires can be self-assembled and self-aligned on flexible substrates opening the route to faster and cheaper plastic electronics.

Orientation patterned (OP)-GaAs crystals have high potential as non linear optical systems. Mid-infrared and terahertz lasers sources can be fabricated with these crystals by frequency conversion from shorter wavelength sources. The optical propagation losses are critical; therefore, the OP-GaAs crystals must have high quality with low incorporation of defects and high homogeneity to reduce the refractive index fluctuations. Defects with electro-optic signature must be characterized in order to reduce their presence. Cathodoluminescence studies of these crystals permit the distribution of the main defects to be established, both extended and point defects. Special attention is paid to the role of the walls between the two domain orientations, and to the incorporation of impurities in Si-doped samples.

Organic materials have been widely used in various fields of electronic applications. However, they are difficult to process without damage by using a conventional ion beam which use energetic ions. In this study, gas cluster ion beam (GCIB), which shows low-damage process, was used for organic materials, and irradiation effect of size selected GCIB was studied with Xray photoelectron spectroscopy (XPS). In the case of irradiation of 500 eV Ar ion (monomer ion) on polyimide, the intensities of both N-C=O and C-O bond decreased after irradiation. On the other hand, there was small change in the XPS spectra after 15 keV Ar-GCIB irradiation with the same ion dose. The etching rate of polyimide per one ion with 15 keV Ar-GCIB was almost 1.8×104 times higher than that with 500 eV Ar monomer ions. The damages in polyimide decreased with increasing the Ar cluster size owing to the reduction of energy per atom at acceleration voltage of 15 kV. After irradiation of size selected 5 kV Ar cluster ion, damage was almost negligible. Although, the surface became rough after irradiation of Ar-GCIB, surface roughness and the change of chemical bond were very small with N2-GCIB irradiation. Ar-GCIB irradiation on dye-sensitized solar cells (N719) showed that very low-damage process is possible with GCIB, and it indicated that GCIB is suitable for surface processing of organic materials used in electronic devices.

We have developed the pressure annealing technique for fabricating low work function metal pattern on plastic substrate. In general, the difficulty to print conductive low work function metal patterns is caused by the insulating metal oxide layer covering on metal particles included in metal paste. The pressure annealing technique can destruct the metal oxide layer and can form conductive layer on printed metal pattern. Further, we have confirmed that a binary solid solution is easily formed on metal patterns including two kinds of metal particles by using the pressure annealing technique. Changing the composition ratio of the binary metal paste led to the work function control of the pressure-annealed metal patterns. Formation of the binary solid solution was confirmed by using XRD spectra, and work function values were measured by using photoelectron emission spectra. In the case of the binary metal paste of Cu and Zn, we have succeeded in controlling work function from 3.8 eV to 5.0 eV. Since the Cu-Zn paste is composed of relatively low price metals, this would be applicable to large-scale flexible electronic devices.

Surface texturing processes for thin silicon solar cells ideally remove as little Si as possible relative to amount of topography generated. Here we describe how a micron-scale quasi-pyramidal texture may be achieved in Si layers with arbitrary crystallinity using a phase-segregated mask in combination with reactive ion etching (RIE). The Si to be textured is coated with a thin barrier layer followed by a layer of Al-Si alloy which phase-segregates into micron-sized regions of Al and Si after low temperature (<450 °C) annealing. One omponent of the mask is selectively etched away and the Si under the exposed barrier regions is etched by a process that gives the desired depth and lateral undercut. In this paper we show the dependence of the segregated Al-Si morphology on Al-Si alloy composition, thickness, and annealing conditions, and then present examples of texturing produced in single crystal Si by these masks in combination with CF4/O2 reactive ion etching.