In a solar photovoltaic cell, how does irradiance affect its I-V characteristics?

• A. Current is proportional to irradiance; Voc increases with temperature
• B. Current is proportional to irradiance; Voc decreases with temperature
• C. Current is inversely proportional to irradiance; Voc decreases with temperature
• D. Current is proportional to irradiance; Voc is independent of temperature

Answer: (C)

Irradiance primarily controls the photogenerated current in a solar cell. The light generates electron–hole pairs, and the resulting photocurrent is nearly proportional to the incident light power, so increasing irradiance pushes the I-V curve upward by increasing the short-circuit current. The open-circuit voltage, on the other hand, is governed by the diode equation and is strongly affected by temperature: as temperature rises, the saturation current increases and the bandgap narrows, causing Voc to fall. So the best description is that current scales with irradiance while Voc decreases with temperature. The other ideas conflict with these well-known trends: current would not decrease as irradiance increases, Voc does not rise with temperature, and Voc is not independent of temperature.