I have researched and looked at several papers describing the effect of temperature on the $I_{sc}$ and $V_{OC}$, and seen many numerical explanations as to why the voltage drops, with reference to I-V curve and other equations, but none actually described why this physically happens. What causes voltage to drop at increased temperatures. Is it the decreased bandgap? It would be appreciable if you could link any related papers that explain this phenomenon physically.
Thanks