Heat mitigation in perovskite solar cells: The role of grain boundaries

Sources of Thermal Power Generation and Their Influence on the Operating Temperature of Organic Solar Cells

“…The ground methodology is based on our previous works [ 14 , 28 , 32 ] on simulating the operating temperature of a perovskite solar cell, where we incorporated the influence of other factors such as grain boundary sizes and tale state recombination rates at the interfaces and grain boundaries. As this paper focuses on OSCs, and organic solids have different properties than perovskites, it is necessary to outline the theoretical details here again, without repetition.…”

“…As this paper focuses on OSCs, and organic solids have different properties than perovskites, it is necessary to outline the theoretical details here again, without repetition. Following our earlier work [ 14 , 28 , 32 ], we have assumed that the OSC operates under the steady state condition, i.e., , where is the operating temperature, and is time. Thus, for an illuminated OSC shown in Figure 2 , we have solved the energy balance equation given by: where is the incident solar radiation ( ), is absorbance, is the solar cell area ( and is the absorbed solar power to generate the photo-excited electron in LUMO and hole in HOMO ( , and it can be written as [ 28 ]: where is the rate of total electron-hole pair generation (s −1 m −3 ), is band gap energy and is active layer thickness ( .…”

“…Some of the electrons and holes generated due to the absorbed solar power, , may recombine non-radiatively and generate the thermal power denoted by and some may generate thermal power by moving to lower energy due to energy off-sets while transferring towards their respective electrodes. Thus, , the total thermal power generated due to the non-radiative recombination of the photo-generated electron and hole pairs, can be expressed as [ 28 ]: where , and are the thermal powers generated at the grain boundaries (GBs), interfaces (Int) and other parts (Other), respectively, in the active layer. The thermal power generated due to the tail state recombination at the GBs can be given by [ 28 ]: where (s −1 m −3 ) is the average tail state recombination rate per unit volume, and is the total volume of GBs (m 3 ).…”

“…Thus, , the total thermal power generated due to the non-radiative recombination of the photo-generated electron and hole pairs, can be expressed as [ 28 ]: where , and are the thermal powers generated at the grain boundaries (GBs), interfaces (Int) and other parts (Other), respectively, in the active layer. The thermal power generated due to the tail state recombination at the GBs can be given by [ 28 ]: where (s −1 m −3 ) is the average tail state recombination rate per unit volume, and is the total volume of GBs (m 3 ). The schematic geometry of GBs is assumed to be spherical of diameter distributed (m) in the whole active layer (the details are presented in our previous work [ 28 ]).…”

“…Despite the above research on the thermal stability of OSCs, the thermal power generating factors which influence the operating temperature, and subsequently the thermal stability, have not yet been quantitatively well studied. The operating temperature of OSCs can depend on both external and internal factors [ 28 ]. The external factors include solar radiation, ambient temperature, wind velocity, sky temperature and surrounding temperature.…”