Depleted hole conductor-free lead halide iodide heterojunction solar cells

Lead halide perovskite is an excellent candidate for use as a light harvester in solar cells. Our work presents a depleted hole conductor free CH₃NH₃PbI₃/TiO₂ heterojunction solar cell using a thick CH₃NH₃PbI₃ film. The CH₃NH₃PbI₃ formed large crystals which function simultaneously as light harvesters and as hole transport materials. We performed capacitance voltage measurements, which show a depletion region which extends to both n and p sides. The built-in field of the depletion region assists in the charge separation and suppresses the back reaction of electrons from the TiO₂ film to the CH₃NH₃PbI₃ film. This depleted hole conductor free CH₃NH₃PbI ₃/TiO₂ heterojunction solar cell provides a power conversion efficiency of 8% with a current density of 18.8 mA cm^-2, the highest efficiency achieved to date for perovskite based solar cells without a hole conductor.