Controllable Photovoltaic Effect of Microarray Derived from Epitaxial Tetragonal BiFeO₃ Films

Recently, the ferroelectric photovoltaic (FePV) effect has attracted great interest due to its potential in developing optoelectronic devices such as solar cell and electric–optical sensors. It is important for actual applications to realize a controllable photovoltaic process in ferroelectric-based materials. In this work, we prepared well-ordered microarrays based on epitaxially tetragonal BiFeO₃ (T-BFO) films by the pulsed laser deposition technique. The polarization-dependent photocurrent image was directly observed by a conductive atomic force microscope under ultraviolet illumination. By choosing a suitable buffer electrode layer and controlling the ferroelectric polarization in the T-BFO layer, we realized the manipulation of the photovoltaic process. Moreover, based on the analysis of the band structure, we revealed the mechanism of manipulating the photovoltaic process and attributed it to the competition between two key factors, i.e., the internal electric field caused by energy band alignments at interfaces and the depolarization field induced by the ferroelectric polarization in T-BFO. This work is very meaningful for deeply understanding the photovoltaic process of BiFeO₃-based devices at the microscale and provides us a feasible avenue for developing data storage or logic switching microdevices based on the FePV effect

Influence of Heterocyclic Spacer and End Substitution on Hole Transporting Properties Based on Triphenylamine Derivatives: Theoretical Investigation

Hybrid organic–inorganic halide–perovskite based solar cells have achieved outstanding progress, approaching one of the most competitive photovoltaic technologies. One of the hot topics is to develop inexpensive and efficient hole transporting materials to improve the performance of devices for practical applications. In this paper, we theoretically design a series of hole transporting materials based on triphenylamine backbone through varying the spacer and the end substitution. The properties of frontier molecular orbital, ionization potential, reorganization energy, and charge mobility have been calculated and analyzed. The results show that the spacer and the end functional groups strongly influence the molecular geometry, stacking, electron density distribution, and especially hole mobility. The best hole transporting material with furan as spacer and hydroxyl or methoxyl as substitution is proposed due to its highest hole transporting mobility induced by the planar conformation and tight π–π stacking, which potentially could enable the highly efficient perovskite solar cells