Characteristics of MAPbI₃ Stacked on the GaN Nanowires-On-Glass

When implementing optoelectronic devices through the stacking of heterogeneous materials, considering the bandgap offset is crucial for achieving efficient carrier dynamics. In this study, the bandgap offset characteristics are investigated when n-type gallium nitride nanowires (n-GaN NWs) are used as electron transport layers in methylammonium lead iodide (MAPbI₃)-based optoelectronic devices. n-GaN NWs are grown on indium-tin-oxide (ITO)-coated glass via the plasma-assisted molecular beam epitaxy (PA-MBE) process to form the “GaN NWs-on-glass” platform. A MAPbI₃ thin film is then spin-coated on the GaN NWs-on-glass. X-ray photoelectron spectroscopy (XPS) shows that the valence and conduction band offsets in the MAPbI₃/n-GaN heterostructure are 2.19 and 0.40 eV, respectively, indicating a type-II band alignment ideal for optoelectronic applications. Prototype photovoltaic devices stacking perovskite on GaN NWs-on-glass show excellent interfacial charge-transfer ability, photon recycling, and carrier extraction efficiency. As a pioneering step in exploiting the diverse potential of the GaN-on-glass, it is demonstrated that the junction characteristics of MAPbI₃/n-GaN NW heterostructures can lead to a variety of optoelectronic device applications.