Interfacial Toughening with Self-Assembled Monolayers for Mechanical Reliability in Inverted Perovskite Solar Cells

Metal halide perovskites (MHPs) have emerged as the most promising light-absorber materials in the photovoltaic community due to their near-ideal bandgaps and extraordinary optoelectronic properties. However, MHPs have extremely poor mechanical properties. They are inherently compliant, soft, and brittle. While significant progress has been made in improving the stability of MHPs, perovskite solar cells (PSCs) will also need to be mechanically reliable if they are to operate efficiently for decades. In this context, we study the mechanical integrity of PSCs by measuring their cohesion/adhesion energies (Gc) using double cantilever beam method. We will then report a novel approach to strategically enhance the interfacial adhesion and performance of p-i-n structure PSCs using carefully designed hole transporting self-assembled monolayers (SAMs), where we find that the perovskite solar cell stability is closely intertwined with its mechanical reliability. This work points to a new route for designing mechanically robust PSCs with long-term durability.