Heterogeneous carbon nano-tube window layer with higher sheet resistance improve the solar cell performance

The heterogeneous Carbon Nano-Tube (CNT) layers deposited on the window surface of solar cells that allow better charge carrier collection was numerically analyzed and studied in modern TCAD tools. The quantum efficiency(EQE) as well as power conversion efficiency (η) were found to be improved significantly based on the light transmission capabilities of the CNT layer. Two CNT network models using experimental sheet resistance values of 75 Ω/ and 128 Ω/ as a top conducting layer in a GaAs solar cell were compared. It is found that the CNT networks allow for a greater area of charge collection as well as serve as a lower resistance path for charge carriers with minimum voltage loss to travel to the top contact. This model thus significantly improve the η up to 30% under AM0 with more than 90% EQE. The effect of cell width varying starting from 200 μm to 4000 μm with CNT top layer on Jsc, Voc and Pmax parameters were studied and found that these parameters remain almost constant irrespective of cell width. This work thus shown that a thin CNT top layers of lower sheet resistance with a higher light transmission can greatly improve the efficiency of solar cells.