Intrinsic Instability of Perovskite Solar Cells: The Role of a Hole-Blocking Layer

Among the emerging photovoltaic technologies, perovskite solar cells (PSCs) are the most promising ones with efficiencies close to crystalline silicon. However, stability and reliability issues are still a limit for future applications of this technology. This manuscript investigates the intrinsic instability of PSCs by focusing on the role of the hole-blocking layer (HBL). PSCs were fabricated employing SnOX and bathocuproine (BCP) as an HBL, and their performances were monitored in time. The two architectures show initial similar performances; hence, they are good candidates for comparison, but they feature different instability phenomena. It is shown that cells fabricated with SnOX present larger instabilities mainly ascribable to open-circuit voltage fluctuations (variations in the short-circuit current are negligible). In contrast, the BCP-based cells are more stable with a marginal increase in their power conversion efficiency that follows the increase in the short-circuit current (while the open-circuit voltage does not change).