SANYO Electric Co., Ltd. (SANYO)
announced today it has broken its own record for the world’s highest energy
conversion efficiency in practical size (100 cm2 or more) crystalline silicon-type
solar cells, achieving a efficiency of 23.0% (until now 22.3%) at a research
level for its proprietary HIT solar photovoltaic cells.
Schematic diagram of the elemental technology
Improving the quality of heterojunction of HIT solar cell
The structure of the HIT solar cell allows a possible reduction in recombination
loss of the electrical element (charged carrier) by surrounding the energy generation
layer of single thin crystalline silicon (c-Si) with high quality ultra-thin
amorphous silicon (a-Si) layers. SANYO has recently managed to improve the quality
of the HIT solar cell junction through developing a technology for depositing
a higher quality a-Si layer over the c-Si substrate while protecting the c-Si
surface from being damaged.
The result was an increase in the open circuit voltage (Voc) from 0.725V to
0.729V.
Reduction of optical absorption loss
In the solar cell, sunlight hitting the surface needs guidance to the c-Si,
the energy generation layer, with the smallest possible absorption loss. For
the HIT solar cell, reducing optical absorption loss in the a-Si layer, which
covers the front and rear surfaces of the c-Si, and the transparent conductive
layer was a challenge. Absorption of short-wavelength solar radiation by the
a-Si layer and that of long-wavelength solar radiation by the transparent conductive
layer were the causes of the optical absorption loss. SANYO has recently developed
know-how to reduce optical absorption loss in both the a-Si and transparent
conductive layers. As a result, the short circuit current (Isc) improved from
39.2mA/cm2 to 39.5mA/cm2.
Reduction of resistance loss
In the solar cell, generated electric current is collected and taken out through
the surface grid electrode. SANYO recently realized lower-resistance electrode
material for use in the grid electrode and a higher-aspect ratio through improving
printing technology, leading to a success in reduction of resistance loss when
an electric current flows through the grid electrode. As a result, the fill
factor (FF) was improved from 0.791 to 0.80.
For the full release and all detailed information, click
here
Posted May 21st, 2009