Influence of compact TiO2 layer on the photovoltaic characteristics of the organometal halide perovskite-based solar cells

A series of perovskite-based solar cells were fabricated wherein a compact layer (CL) of TiO2 of varying thickness (0–390 nm) was introduced by spray pyrolysis deposition between fluorine-doped tin oxide (FTO) electrode and TiO2 nanoparticle layer in perovskite-based solar cells. Investigations of the CL thickness-dependent current density–voltage (J–V) characteristics, dark current, and open circuit voltage (Voc) decays showed a similar trend for thickness dependence. A CL thickness of 90 nm afforded the perovskite-based solar cell with the maximum power conversion efficiency (η, 3.17%). Furthermore, two additional devices, perovskite-based solar cell omitting hole transporting materials layer and cell without the TiO2 nanoparticles, were designed and fabricated to study the influence of the CL thickness on different electron transport paths in perovskite-based solar cells. Solar cells devoid of TiO2 nanoparticles, but with perovskite and organic hole-transport materials (HTMs), exhibited sustained improvement in photovoltaic performances with increase in the thickness of CL, which is in contrast to the behavior of classical perovskite-based solar cell and common solid state solar cell which showed optimal photovoltaic performances when the thickness of CL is 90 nm. These observations suggested that TiO2 nanoparticles play a significant role in electron transport in perovskite-based solar cells.