Discrete Aluminum Oxide Surface Passivation Enables High Efficient Cadmium Telluride Solar Cells

Cadmium telluride (CdTe) thin film has attracted significant attention in photovoltaic applications due to its high optical absorption coefficient and long‐term stable performance. However, the undesired back contact still worsens the charge carrier transport and thus hinders the power conversion efficiency (PCE) of CdTe solar cells. In this study, discrete aluminum oxide (Al 2 O 3 ) nanoparticles are developed as a passivation layer to modify the back interface between the CdTe absorber and the Au electrode. The results demonstrate that the poorly coated Al 2 O 3 nanoparticles do not lead to an increase in resistance. In addition, the carrier lifetime improves after Al 2 O 3 nanoparticles are involved, which allows more efficient charge carrier transport at the back contact interface. Finally, the CdTe solar cell exhibits significantly improved fill factor and open‐circuit voltage ( V OC ) of 74.81% and 848 mV, with a PCE of 17.45%. These results disclose new insights into addressing key challenges that hinder the development of CdTe solar cells.