Origin of sputter damage during transparent conductive oxide deposition for semitransparent perovskite solar cells

Abstract

Transparent conductive oxides (TCOs) have been widely used as transparent electrodes in numerous optoelectronic devices including perovskite/silicon tandem solar cells. A significant concern regarding the application of TCOs is the sputter-induced damage to the underlying films. Understanding the source of this damage and finding ways to mitigate it are crucial to improve the design of solar cells. In this study, a systematic investigation was performed to determine the origin of TCO sputtering damage on the perovskite/C₆₀ stack using various optical filters and a series of sample structures. Our results revealed that the steady-state photoluminescence intensity increased when the perovskite/C₆₀ stack was only exposed to plasma radiation. This finding suggests that sputtering damage originates from ion bombardment rather than plasma radiation. X-ray diffraction analysis indicated that the plasma radiation involved in the sputtering process could release the lattice strain in the perovskite film. Furthermore, both simulations and experiments illustrated that sputtering damage was associated with the formation of defects in the C₆₀ layer and the dissociation of CN bonds at the perovskite surface due to ion-bombardment-induced phonon propagation. A method to mitigate this damage using a SnO_x buffer layer was experimentally confirmed, and its working mechanism was elucidated.