Solar panel efficiency is affected by temperature, and generally, as the temperature increases, the efficiency of the solar panel decreases. This phenomenon is known as the temperature coefficient of the solar panel.

The efficiency of a solar panel is typically specified at a standard test condition (STC) of 25 degrees Celsius (77 degrees Fahrenheit). At this temperature, the solar panel’s efficiency is measured under specific laboratory conditions that simulate full sunlight.

As the temperature of the solar panel increases above the STC, several factors contribute to the reduction in efficiency.

• Increased Electron Mobility: With higher temperatures, the mobility of electrons in the semiconductor material of the solar panel increases. This can lead to more electron-hole recombination, reducing the overall current output of the solar cell.

• Bandgap Energy: The bandgap energy of the semiconductor material decreases with increasing temperature. This means that the energy required to create electron-hole pairs becomes smaller, leading to more thermal generation of electron-hole pairs instead of relying on photons from sunlight.

• Voltage Drop: The open-circuit voltage of the solar panel decreases with temperature, which also impacts its overall performance.

The temperature coefficient is a measure of how much the efficiency decreases for each degree Celsius increase in temperature above the STC. The temperature coefficient is typically expressed as a percentage per degree Celsius (%/°C). For example, if a solar panel has a temperature coefficient of -0.4 %/°C, it means that for every degree Celsius increase above the STC, the panel’s efficiency will decrease by 0.4%.

It’s important to note that while higher temperatures reduce the efficiency of the solar panel, they can also lead to an increase in the actual power output (wattage) due to the increased sunlight absorption. However, the efficiency decrease usually outweighs the increase in power output, resulting in a net reduction in the overall efficiency of the solar panel.

Solar panel manufacturers provide temperature coefficient specifications, which can help users understand how their panels will perform under different temperature conditions. Installing solar panels in a well-ventilated area and maintaining proper airflow beneath them can help mitigate the negative effects of high temperatures on efficiency and overall performance.