Temperature Performance of Thin-Film PV
One of the advantages of thin-film PV is the superior high-temperature performance, which results in higher efficiency compared to standard crystalline wafer-based silicon PV. For all solar cells, the efficiency begins to drop once the panel temperature exceeds 25°C (77°F), and this drop is quantified using a metric known as the “temperature coefficient.” The temperature coefficient relates the the loss in efficiency observed for each one degree increase in the temperature (ie. % / °C).
The result in electrical output decreases by two factors:
Under strong sunlight the solar cell temperature will increase
If ambient temperatures are high, then the solar module will have a decreased ability to vent waste heat.
The consequence of higher solar cell temperatures is not only lower electrical output, but also an accelerated degradation of the solar cell.
For traditional PV, the typical observed high-temperature performance degradation is:
For crystalline-silicon: about 0.45% decrease in efficiency per °C
For CdTe and CIGS: about 0.3% decrease in efficiency per °C
As an example, a traditional crystalline silicon solar cell that performs at 20% efficiency at 25°C (77°F), in a high sunlight environment (e.g., Abu Dhabi, UAE, or Phoenix, Arizona) at noon, the internal solar cell temperature can reach 85°C (185°F) and higher, and the efficiency would drop from 20% down to about 14.6%.
As the solar cell thickness decreases, the impact of high temperature on electrical performance also decreases. Thinner solar cells have a higher surface area in proportion to volume, so they can vent excess heat more rapidly, maintaining a lower cell temperature and keeping closer to the rated efficiency. Reducing crystalline silicon solar PV thickness by about a half has shown for one product on the market to reduce this temperature coefficient by about a half.
For PI Energy’s ultra-thin solar cell, at about 1/40 the thickness of traditional crystalline silicon, we expect the temperature coefficient to be significantly lower, enabling higher performance in high-temperature conditions, which are common when solar energy resources are plentiful.