Heat dissipation in perovskite solar cells with different grain shapes

Heat dissipation in solar cells has been rarely presented in the literature despite a critical role in the thermal and electrical stability of these thermodynamic devices. We have simulated the heat dissipation through the grain structure of perovskite solar cells assuming grains with the single large size and shapes to facilitate the simulation of randomly shaped grains in real devices. To facilitate this, we converted the randomly shaped grains into large single rectangular and cylindrical grains and developed a coupled electrical-thermal model to investigate the heat dissipation and temperature distribution across the grain interior and boundaries. Heat generation via non-radiative recombination and joule heat (in bulk) and tail state recombination heat (in grain boundaries) versus the radiative and convective cooling were inserted in the calculations. It seems that grain geometry and shape (width, length, and thickness) have a vital impact on heat dissipation from the interior bulk of grain, and the grain boundaries act as cooling sources for the perovskite layer. The cylindrical-shaped grain shows a better cooling capability because of a smaller contact area with adjacent grains. The cylindrical grains can also compensate for the disadvantage of high surface traps, short carrier lifetime, and high surface recombination velocity at grain boundaries and protect the heat-sensitive perovskite layer against heat accumulation and decomposition.