Molecular Doping for Hole Transporting Materials in Hybrid Perovskite Solar Cells

Hybrid lead halide perovskites have been revolutionary in the photovoltaic research field, reaching efficiencies comparable with the most established photovoltaic technologies, although they do not yet reach their competitor stability. The search for a stable configuration required the engineering of the charge extraction layers; in this work, molecular doping is used as an efficient method for small molecule and polymer, employed as hole transport materials in planar heterojunction configuration on compact-TiO2. We proved the viability of this approach, obtaining significantly increased performances and reduced hysteresis on compact titania-based devices. We investigated the photovoltaic performance, correlating to the hole transport material structure. We have demonstrated that the molecular doping mechanism is more reliable than the oxidative doping, and verified that molecular doping in polymeric hole transport materials leads to highly efficient perovskite solar cell, with long-term stability.