Impacts of Tunnel Junction Thickness on the Performance of Triple-Junction Solar Cells

This paper presents a study on the impact of tunnel junction thickness on the performance of multijunction solar cells. Extensive research into this area was performed on two samples of triple-junction InGaP/InGaAs/Ge solar cells (P1, P2) with active layers of different thicknesses. The effects of the tunnel junction thickness influence on cell performance were investigated. The experiment was carried out at light intensity levels of 600, 800 and 1800 W/m², with cell temperatures in the range of 25–50 °C. From the dark and light I–V curves, cell characteristic parameters were obtained. Performance parameters like the fill factor (FF) and efficiency (η) were calculated. Acquired results show a clear dependence light concentration on short circuit current (I _sc) and the maximum power (P _max) of P1 and P2. It can also be stated that the current parameters of solar cells are slightly affected by temperature. The main purpose of this study was to investigate the relationship between tunnel junction thickness and solar cell performance, which is a parameter of particular interest of solar cell and CPV system manufacturers. The experiment showed that electrical behavior of both samples may be influenced by differences in thicknesses of active layers, but also by not sufficiently dopping levels and variability of parameters during manufacturing.