Mitsubishi Announces 18.9% Conversion Efficiency Rate For Multi-Crystalline Silicon PV Cells

February 23, 2009 by Jeff Shepard

Mitsubishi Electric Corp. announced that it has improved what it describes as its world’s highest conversion efficiency rate for a 150 x 150mm practical-size multi-crystalline silicon photovoltaic (PV) cell by 0.3 points from 18.6% to achieve a new world record of 18.9%.

In addition to the technology already developed by Mitsubishi Electric to improve the photoelectric conversion efficiency rate in multi-crystalline silicon PV cells, the company states that it has developed a new method to efficiently absorb infrared rays in sunlight, thus achieving a new world record of 18.9%.

To increase the photoelectric conversion efficiency rate in PV cells, it is important to absorb and generate electricity efficiently from a wide range of wavelengths in sunlight. Due to the characteristic of crystalline silicon, which has difficulty in absorbing infrared rays, only roughly half of the infrared rays in sunlight can be used to generate electricity, while the other half is usually lost as heat energy after reaching the rear surface of silicon cells. In particular, the thinner the silicon PV cell is, the more difficult it becomes to absorb infrared rays.

Mitsubishi Electric has succeeded in improving efficiency in utilizing infrared rays by 26% compared to the company’s previous PV cells, whose development was announced in March of 2008. The newly developed PV cell has a rear-surface reflection structure, which reflects infrared rays that reaches its rear surface to allow the cell to absorb more light.

To increase the photoelectric conversion efficiency rate in PV cells, it is also important to reduce the amount of light reflected from their front surface to take more sunlight into the cells. This newly developed PV cell adopts the same low-reflective honeycomb-textured structure as the one previously developed by Mitsubishi Electric that achieved a 18.6% conversion efficiency rate.

Mitsubishi Electric will begin introducing this multi-crystal silicon PV cell technology into mass-produced PV modules from fiscal 2011 (April 1, 2010-March 31, 2011). Mitsubishi Electric also aims to increase output of PV systems by combining this technology with its PV inverters, which have a high energy-conversion efficiency rate. The company intends to continue its R&D to improve efficiency in PV systems, thus contributing to environmental preservation and achieving a sustainable society.