# How does increasing temperature reduce the efficiency of solar cells?

I've seen several answers and trying to confirm.

1) Does temperature increase the ground state energy of electrons once they reach the positively doped semiconductor, thus reducing the voltage between excited electrons from negatively doped semiconductor and ground state they will reach on positive side.

-This was the most compelling and easy to understand answer for me.

-However I'm not sure if it makes sense that "ground states" would rise with increasing temp.

2) Does temperature increase vibrations in wires and semiconductors, such that excited electrons following voltage difference lose energy in collisions along their path from N-doped to P-doped?

Combination of the two? Am I way off?

I am a molecular biology student with some basics in photochemistry. Somewhat familiar with solar cells and looking to dive deeper on the subject so feel free to reference.

As the temperature increases, the diffusion lengths in Si and GaAs will increase ... and the minority lifetime increases with temperature. The increase in minority-carrier diffusion length causes an increase in $$J_{L}$$. However, $$V_{oc}$$ will rapidly decrease because of the exponential dependence of the saturation current on temperature. The increase in the "softness" (roundness) in the knee of the $$I-V$$ curve as temperature increases will also degrade the fill factor. Therefore, the overall effect causes a reduction of efficiency as the temperature increases.
Here, $$J_{L}$$ is the current caused by light generation of electron-hole pairs. So, it goes up. But, the device is still a diode and must follow the standard diode equation, so the open circuit voltage ($$V_{oc}$$) drops. This then also impacts the power output.