Measurement and Simulation of Hot Spots in Solar Cells - ScienceDirect
Analytical modeling of the temporal evolution of hot spot temperatures in silicon solar cells: Journal of Applied Physics: Vol 123, No 9 (scitation.org)
The hot spot is formed when one of the cells becomes shadowed in a module whos solar cells are connected in series. It is so that the this shadowed solar cell becomes reverse biased. This cell and the load resistance RL will be derived by the un shadowed forward biased cells in the module. If the solar cell has hard I-V reverse I-V characteristics then it will reach its rated breakdown voltage. If it has soft reverse I-V curve it will has thermal breakdown.
Most of the solar cells have soft reverse I-V curve and this can be easily proved by measuring the reverse I-V curve of samples of solar cells.
We come to the important point.
The reverse current in the solar cell will be limited by the module load resistance.
Knowing this operating point is staring point of the temperature calculation.
The electric power dissipated in the solar cell will be dissipated in a small area of the solar cell where the reverse current flows. This area will be hot and therefore called the hot spot.
One can then model the the heat flow from the hot spot to the surrounding by its electrical equivalent circuit which can be used to estimate the rise of the temperature at the hot spot due to dissipated heat flow through it.
To see the thermal flow model please follow the paper in the link:Presentation comprehensive study of the pin diodes