Modifying the polycrystalline silicon solar cell by reducing the thermal resistance of the ethylene vinyl acetate (EVA) layer is essential to enhance the thermal management process. This modification will improve the heat dissipation process from the silicon wafer especially at a higher solar concentration ratio (CR) and in return enhance the solar cell performance and output power. Thus, a modified design of a solar cell integrated with a microchannel heat sink is developed. In this new design, variations of the Ethylene-Vinyl Acetate (EVA) upper- and lower-layer thickness along with the interval width between the two consecutive silicon layers are investigated. To determine the effect of varying the design parameters on the cell temperature at various solar concentration ratios and coolant mass rates, a three-dimensional comprehensive model for the solar cell integrated with a heat sink is developed. The model is simulated and validated with numerical results and measurements. Results indicate that reducing the EVA lower layer thickness has a remarkable effect on the solar cell temperature. At a solar concentration ratio of 20, varying the EVA lower layer thickness from 1.0 mm to 0.2 mm results in decreasing the maximum cell temperature from 102.3 degrees C to 69.3 degrees C. With further increase of the concentration ratio up to 30, the maximum cell temperature reduces from 138.3 degrees C to 87.4 degrees C. It is found that at a coolant rate of 2000 gm/min, and a concentration ratio of 20, maximum temperature in the modified and conventional solar cell with a lower EVA thickness of 0.2 mm and 0.5 mm, reaches 69.3 degrees C and 81.5 degrees C, respectively. Furthermore, the conventional cell efficiency is about 8.90%, while the modified one achieves 9.6%. At a CR = 30, the maximum temperature of the modified cell is 87.4 degrees C, while it is beyond the permissible temperature for the conventional cell. However, the solar cell temperature was not affected by varying the EVA upper layer and the interval width between the silicon layers. The finding of the current results provides another direction for researchers to utilize a higher concentration ratio with polycrystalline silicon solar cells.