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 TiO 2 of varying thickness (0–390   nm) was introduced by spray pyrolysis deposition between fluorine-doped tin oxide (FTO) electrode and TiO 2 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 ( V oc ) 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 TiO 2 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 TiO 2 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 TiO 2 nanoparticles play a significant role in electron transport in perovskite-based solar cells.