How does increasing temperature reduce the efficiency of solar cells?
While perhaps better suited to Physics SE, I will quote from Sze's Physics of Semiconductor Devices: 


  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. 

In brief, neither of your proposed reasons is the basis for it. Instead, you have to probe deeper into the physics of semiconductor devices.