Katsuhiko Hayashi

Large area thin film Si module

Abstract An initial efficiency of 14.1% ( J sc =13.6xa0mA/cm 2 , V oc =1.392xa0V, FF=74.3%) has been achieved for a-Si/transparent interlayer/poly Si solar cell (total area of 1xa0cm 2 ). Both a-Si and crystalline Si films were fabricated by plasma chemical deposition at low temperature. The short circuit current was enhanced by the introduction of a transparent intermediate layer. An initial aperture efficiency of 11.7% has been achieved for 910×455xa0mm 2 a-Si/poly Si integrated solar cell submodule, where the laser-scribing techniques were applied for series interconnections. The results of our first run of 266 submodules in our pilot plant showed the average efficiency of 11.2%, which is applicable for mass production.

High efficiency thin film silicon solar cell and module

An initial efficiency of 14.5% (Jsc=14.4mA/cm/sup 2/, Voc=1.41V, FF=71.9%) has been achieved for a-Si:H/transparent inter-layer/crystalline Si solar cell (total area of 1cm/sup 2/). Both a-Si and crystalline Si films were fabricated by plasma chemical vapor deposition at low temperature. The short circuit current (Jsc) was enhanced by the introduction of transparent interlayer without increasing the thickness of a-Si:H layer. An initial aperture efficiency of 12.3% has been achieved for 910/spl times/455mm/sup 2/ a-Si/crystalline Si thin film integrated solar cell module. Reasonably high deposition rate of 11 A/s for the deposition of crystalline Si for 1/spl times/1m/sup 2/ area has been achieved. By applying a deposition conditions of this high deposition rate, an initial aperture efficiency of 11.2% has been obtained above sized Si stacked solar cell module.

Effective conversion efficiency enhancement of amorphous silicon modules by operation temperature elevation

Abstract To eliminate photo degradation, we have proposed the elevation of the operating temperature of amorphous silicon modules by thermal insulators (polystylene foam) attached to them. A solar cell which degraded 19% with ordinary accelerated test condition (AM 1.5, 1 kW/m 2 , 48°C, 550 h) degraded only 13% at 90°C. The temperature coefficient of amorphous silicon solar cell is about 2 3 of that of crystalline silicon solar cells. A simple calculation predicts about 80% of the initial efficiency in actual operation. Modules whose initial efficiency is about 9.2% were field on 1 April 1996. These modules showed more than 8% effective efficiencies on 21 August 1996. The cell temperature elevation by thermal insulation depends not on the ambient temperature but on insolation and wind speed, and is about 8°C on average and 40°C at peak. Effective conversion enhancement by temperature elevation is about 1% of the conventional one, which can be larger in later observation.

Low-cost amorphous silicon photovoltaic module encapsulated with liquid resin

To reduce the cost of amorphous silicon photovoltaic modules, a monolithic structure and an encapsulation process with liquid resin has been developed. The line speed of the encapsulation process can be up to 190 cm/min with a simple apparatus, which corresponds to 40 MW/y. The process was applied with actual amorphous silicon photovoltaic modules with a size of 910 × 455 mm2. The aperture efficiency of the photovoltaic module was 10.6% (41.9 W). The modules passed five acceleration tests stated in JIS C 8917, i.e., dump-heat test, salt-mist cyclic test and humidity-freeze test. Field tests which have been carried out in Japan and Arizona assured that the encapsulation with liquid resin is as reliable as the conventional encapsulation with EVA/Tedler. The cost of the liquid resin could be reduced to 80% of original one without reducing reliability, by investigating the recipe of an organic compound.

Large-area and high efficiency a-Si/poly-Si stacked solar cell submodule

An initial aperture efficiency of 11.57% or an average output of almost 43.24 W has been achieved for 910/spl times/455 mm/sup 2/ a-Si:H/poly-Si integrated solar cell submodule, where laser-scribing techniques were applied for series interconnections. Both a-Si:H and poly-Si were fabricated by plasma chemical vapor deposition at low temperature, respectively. The outdoor measurements of their module, made in early September in Shiga, Japan, showed the good coincidence of their indoor measurements which were performed by a double light source solar simulator. The results of stability experiments by using an alternative minimodule showed a more than 10% efficiency of their submodule.

ZnO-Ag sputtering deposition on a-Si solar cells

In order to produce large area amorphous silicon solar cell modules and to simplify the module production process, a continuous ZnO/Ag sputtering deposition process has been applied. The authors found that by means of a continuous ZnO/Ag sputtering deposition method, an adhesive a-Si/electrode contact can be realized. They compared short circuit currents of Al,ZnO/Al and ZnO/Ag back side contact cells and confirmed short circuit current increase by application of ZnO/Ag back side contact. They found that the series resistance is severely depend on the conditions during the first stage of ZnO deposition. They confirmed the reliability of ZnO/Ag structure as the back side contact through high temperature high humidity tests. After 310 hours of an accelerated light induced degradation test, which corresponds to one year light exposure, a 100 cm/sup 2/ integrated a-Si tandem solar cell kept an efficiency higher than 8.5%.

New type of large-area a-Si module produced using a polymer encapsulation method

A new type of amorphous silicon (a-Si) solar module has been developed, the back surface of which is encapsulated with a thermosetting polymer by using a spreading method. For this purpose, poly-olefin oligomer was chosen as an encapsulation layer and the process has been investigated. The modules show very little change in electrical performance under several types of acceleration test.