Hysteresis Effects\nin Photovoltaic Devices Based on\na Two-Dimensional Molecular Ferroelectric

Narrow bandgap two-dimensional molecular ferroelectric\nmaterials\nhave enormous potential in the field of optoelectronics, but excellent\nspecies are still scarce. (4-Iodobutylammonium)<sub>2</sub>­(methylammonium)<sub>2</sub>­Pb<sub>3</sub>I<sub>10</sub> (IBMPI) has been demonstrated\nto be a low-bandgap two-dimensional biaxial mixed perovskite molecular\nferroelectric. In this work, we used IBMPI as the light-absorbing\nlayer to fabricate p-i-n structured photovoltaic devices. Under the\nirradiation of AM 1.5 G, the IBMPI-based solar devices exhibit significant\nphotovoltaic effects (<i>V</i><sub>OC</sub> ≈ 0.78\nV, <i>J</i><sub>SC</sub> ≈ 5.07 mA/cm<sup>2</sup>). In addition, by adjustment of the bias history, the intrinsic\nferroelectric polarization and ion migration in IBMPI can also be\nused to adjust photovoltaic performance, especially the open-circuit\nvoltage and fill factor. This work indicates that this two-dimensional\nmolecular ferroelectric is a potential candidate material for preparing\ntunable photovoltaic devices.