# What is the relation between efficiency of solar cella and incident light power $\eta(P_{inc})$?

What mathematical relation, if there is one usually valid, describes the variation of efficiency $\eta$ of a solar cell (i.e. the ratio of produced electrical power $P_{el}$ and incident light power $P_{inc}$) and incident light power $P_{inc}$ itself?

In other words, what is the typical form of the relation $\eta(P_{inc})=f(P_{inc})$ ?

• It's about 20%. BTW I have no idea what f(Pinc) is. – Andy aka Mar 7 '17 at 18:49
• Someone asked about this recently. After a brief google search, I learned that in principal, efficiency goes up with higher irradiance. But there is a maximum at which efficiency peaks and then starts to go back down. I believe most solar panels are designed so full direct sunlight is right at the efficiency maximum. So increasing irradiation beyond that will not improve efficiency. but there is a term you may want to google: concentrator photovoltaics. Also see this: lirias.kuleuven.be/bitstream/123456789/359665/1/4BV.4.54.pdf – mkeith Mar 8 '17 at 5:39

## 1 Answer

You are correct that efficiency increases (asymptotically) with increasing irradiance at constant cell temperature. However, in practice, higher irradiance increases cell temperature so the efficiency gains may be nearly nullified by the temperature-effect loss.