Improve Hole Collection by Interfacial Chemical Redox Reaction at a Mesoscopic NiO/CH3NH3PbI3 Heterojunction for Efficient Photovoltaic Cells. Issue 17 (22nd June 2016) - Lin, Ming‐Wei
Abstract : Organometal‐trihalide‐perovskite‐based solar cells have exhibited high efficiencies when incorporated into mesoscopic NiO (NiOnc ) hole‐transport layers. The integration of a NiOnc ‐perovskite heterojunction provides an inorganic alternative as a p‐type contact material with efficient hole extraction for perovskite‐based solar cells. Herein the origin of such highly efficient carrier transport is studied in terms of electronic, chemical and transport properties of a NiOnc ‐perovskite heterojunction with X‐ray photoelectron spectra, ultraviolet photoelectron spectra, near‐edge X‐ray absorption fine structure spectra, a scanning transmission X‐ray microscope, and calculations of electronic structure. A pronounced chemical redox reaction is found at an NiOnc ‐perovskite heterojunction such that PbI2 is oxidized to PbO with subsequent formation of hole‐dopant CH3 NH3 PbI3–2δ Oδ at the heterojunction. The generation of hole‐doping CH3 NH3 PbI3–2δ Oδ induced by the redox reaction at the NiOnc /perovskite heterojunction plays a significant role to facilitate the carrier transport, and thus enhances the photovoltaic efficiencies. Abstract : A pronounced chemical redox reaction at an NiOnc ‐perovskite heterojunction to form the hole‐dopant CH3 NH3 PbI3–2δ Oδ is determined. This interfacial hole‐doping CH3 NH3 PbI3–2δ Oδ and NiOnc exhibits superior electronic properties to bring about the energy matching of NiOnc /perovskite interface and enable faster hole transport.