“Efficiency is close to internal combustion engine. This is the conversion efficiency to achieve the ideal of breaking 50% of the solar cells in the process of a major breakthrough” (Sharp). Recently, Sharp,
Inspiron E1505 battery the conversion efficiency of solar cells increased to a record 35.8%. If the condenser to 1000 times the conversion efficiency is also expected to reach 45%.
Sharp’s technical staff the ongoing new round of development. Objective is to 1 / 10 the cost of non-condensing unit when the conversion efficiency exceeded 40%. To go beyond 40% as the goal is not to intensify the development of a Sharp.
laptop battery In order to achieve high efficiency solar cells, the technology development of competition are becoming more active.
Prior to this, the highest conversion efficiency is the U.S. NREL (National Renewable Energy Laboratory) in 2007, created by 33.8%. Condenser under the conditions of maximum efficiency Spectrolab is the United States in October 2009 just posted on the Institute 41.6%. Including Sharp, including the results of this and create a record of all compounds for the three-in-style multi-junction solar cells.
The solar cell conversion efficiency to the limit and need to combine different materials band gap in order to take full advantage of the various wavelengths of light. Sharp focus on the past, manufacturing simplicity, chose the lattice constant close to the material. Namely, the top unit (the upper three-junction structure) of InGaP, the unit (ibid., middle) as InGaAs, at the end of unit (ibid., lower) for Ge, bottom of Ge.
This time, Sharp to optimize the band-gap for the first, at the end of unit Ge (bandgap of 0.67eV) from the InGaAs (ibid., 0.97eV) substitution, using InGaP (top), GaAs (China), InGaAs (bottom), GaAs backplane combinations. Therefore, in accordance with the order from top to bottom, from short to long wavelengths of light can be applied effectively to generate
electricity.
Solve the issue through the Reverse Cascade
This combination exists InGaP and GaAs lattice constants, and other bottom layer of quite different issues. This phenomenon may give rise to crystal defects, it is difficult to achieve high efficiency. To this end, Sharp turned the film over the past order, through the use of from the InGaP (top) began in turn film “reverse cascade formation method” so that the lattice constant of GaAs substrate basically reached a consensus. Through the lattice constants of the different GaAs (middle) and InGaAs (bottom) inserted between the buffer layer, inhibiting defects. Taking into account the transmission wavelength, the buffer layer and top with the InGaP.
Forming method using the reverse cascading from the InGaP (top) began in turn to the superposition of InGaAs (bottom), the three-layer GaAs substrate need to separate, InGaAs (bottom) layer down to the Si substrate on the transfer. InGaP layer in a direction to the surface. Bonding with the Si substrate to use is “similar to the solder material” (Sharp).
In addition to more efficient, the method can also reduce costs in the future. GaAs substrate separation process is currently used by curettage GaAs substrate method. If in the future to take advantage of plug stripped layer, who wish to divest part of the implementation of ion implantation and other methods to complete the process, then, GaAs substrate is expected to achieve reuse. As the GaAs substrate is very expensive, so the realization of this method can significantly reduce costs.
With these improvements, “than crystalline Si-high two-digit,” is expected to reduce manufacturing costs to the current 1 / 10. Its use is currently limited to satellite, but with lower costs in the future may also be extended to other areas.
Enhancement of conversion efficiency does not stop there. 2025, Sharp plans to develop a cell conversion efficiency of 40%, 1000 times the condenser when the conversion efficiency of 50% of the revolutionary solar cells. Through the InGaAs (bottom) below the addition of new layers, to achieve four resultant compound multi-junction solar cells. Manufacturing methods is still the method of reverse cascade formation. In addition to the different band gap materials, the use of quantum dots band gap control layer is also expected to become a new layer.
South Korea’s LG and Taiwan’s AU Optronics (AUO) is scheduled to “Green Device 2009 Forum” (10/28 ~ 10/30) held on to explore the solar cell business and technology strategy seminar solar cells.