Sharp Develops Solar Cell with World's Highest Conversion Efficiency of 35.8%

October 22, 2009

Sharp Corporation has achieved the world's highest solar cell conversion efficiency (for non-concentrator solar cells) of 35.8% using a triple-junction compound solar cell.

Unlike silicon-based solar cells, the most common type of solar cell in use today, the compound solar cell utilizes photo-absorption layers made from compounds consisting of two or more elements such as and gallium.

Due to their high conversion efficiency, compound solar cells are used mainly on space satellites. Since 2000, Sharp has been advancing research and development on a triple-junction compound solar cell that achieves high conversion efficiency by stacking three photo-absorption layers.

To boost the efficiency of triple-junction compound , it is important to improve the crystallinity (the regularity of the atomic arrangement) in each photo-absorption layer (the top, middle, and bottom layer). It is also crucial that the solar cell be composed of materials that can maximize the effective use of solar energy.

Conventionally, Ge () is used as the bottom layer due to its ease of manufacturing. However, in terms of performance, although Ge generates a large amount of current, the majority of the current is wasted, without being used effectively for electrical energy. The key to solving this problem was to form the bottom layer from InGaAs (indium ), a material with high light utilization efficiency. However, the process to make high-quality InGaAs with high crystallinity was difficult.

Sharp has now succeeded in forming an InGaAs layer with high crystallinity by using its proprietary technology for forming layers. As a result, the amount of wasted current has been minimized, and the , which had been 31.5% in Sharp’s previous cells, has been successfully increased to 35.8%.

Provided by Sharp

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Oct 22, 2009
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5 / 5 (3) Oct 22, 2009
"for non-concentrator solar cells"
2.2 / 5 (5) Oct 22, 2009
The electric car moves one step closer.
A bank of cells on the roof and boot lid should allow the average commuter a free ride if the sun is shining, topping up the battery while the car is parked.
5 / 5 (4) Oct 23, 2009
No. Do the math. Even if you convert 100% of the sunlight on a car roof at midday without any cloud cover you would not get nearly enough energy to run a car.
5 / 5 (3) Oct 23, 2009
NREL Solar Cell Sets World Efficiency Record at 40.8 Percent

This is for a concentrated PV cell- that one had the power of 326 suns hitting it at at once to achieve 40.8% eff
1.8 / 5 (4) Oct 23, 2009
No. Do the math. Even if you c...

According to a joint venture study by the USGS and DOE under ideal atmospheric conditions (death valley) and with only single axis sun tracking, a black painted sheet of steel is hit for up to 16kwh/m2 per hour of sunlight. Which is enough to run a 20 hp engine full throttle per hour- but nobody is driving around with their pedal to the floor for 60/60 minutes, even if you hit 30/60 you would still have 30 minutes of 40hp full throttle, 10/60 minutes and you have you guessed it 120hp and what are the distances you drive- this may actually be more then enough energy to expediently get you where you are going. Especially if you have good energy storage systems since you get to add all the hours of sunlight you are not driving, but parked in the light. Actually in a day a square meter can be hit by enough energy to drive a 300HP motor full throttle for an hour fairly easy. A car roof is usually not a square meter though, but with hood and trunk
1 / 5 (1) Oct 23, 2009
Did they publish the results in any academic publication?
5 / 5 (5) Oct 23, 2009
"up to 16kwh/m2 per hour"

Interesting, as in space with no atmosphere, solar flux is only 1365 watts/m2. Your quoted value is the maximum daily total, not hourly. For a tracking system, in Death Valley, on a summer day.
4.3 / 5 (6) Oct 23, 2009
For a realistic value: 500 langleys per day or 5.8 kw-hr on meter-square normal surface. Discount that to 1.2 kw-hr for a horizontal surface. Assume 35% conversion and 90% storage efficiency. That's less than 400 WATT-hours per square meter on a car's surface. Not much. (It took me a while to track down my solar engineering references.)
2.7 / 5 (3) Oct 23, 2009
Atmospheric lensing raises the concentration, and their published result was for the entire country regionally divided which came to 5.5-12kwd/mm2 per day averaged over a year with one axis tracking (up/down facing south) But the peaks in desert regions hit up to 15kwh, 15 100 watt light bulbs which put out about 1350 watts of heat would not come close to evaporating as much water as a 1 square meter plate of steel painted bbq
1.3 / 5 (3) Oct 23, 2009
A 100 watt lightbulb in room temperature conditions will heat most side surfaces to 106 degrees at 6 inches distance, 150 watt hits around 117, and they put out about 90% heat, the ground at death valley can hit 200 degrees which would require about 570 watts, now how many bulbs you think you would need to make a 1 meter square surface 200 degrees while being a fair insulator (plenty of air in sand and dry soil). well a 12 inch diameter sphere, would have 140 sq inch of surface area, a square meter has around 1474- so at least 10.5 bulbs (5.7kw) of heat is applied. (death valley air temperature at night hits room temperature, but the ground is much lower- so 5.7kw/h per hour of applied heat is a minimum peak- based on insulative and IR absorbing properties of sand/dry soil up to 30% of the heat bounced off the ground entirely. Yes 15kwh is a very high number but it is not indicitive- the national average over the year was 5.5-9kwh
5 / 5 (1) Oct 26, 2009
Solar density is 1.4kW per square meter. You are limited by the number of square meters you have on your car. Either you plaster your car with solar panels or plaster only a small amount of your car with solar panels and use a concentrator (doing both is pointless as can be easily imagined).

It doesn't matter which way you go you can't achieve more than those 1.4kW times the amount of square meters on your car.

A sizeable car (Mercedes CL) is 5m by 2m. So you'll get 14kW (about 19hp) MAXIMUM at midday in death valley. You aren't going anywhere with 20hp and a car that size (especially not in normal weather conditions, during commuter times (morning/evening)).

For a small car (like a VW rabbit) you get about 10hp. Again: this is MAXIMUM at 100% efficiency. With real efficiency ratings of solar panels (50%) and weather conditions? Most lawn mowers/golf carts will outperform you.

Lugging around additional batteries with an underpowered vehicle is not an option here.

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