Ultrahigh Bulk Photovoltaic Effect Responsivity in Thin Films: Unexpected Behavior in a Classic Ferroelectric Material

Abstract

The bulk photovoltaic effect (BPE) has drawn considerable attention due to its ability to generate photovoltages above the band gap () and reports of highly enhanced photovoltaic current when using nanoscale absorbers or nanoscale electrodes, which however do not lend themselves to practical, scalable implementation. Here, we show that a strikingly high BPE photoresponse can be achieved in an ordinary thin‐film configuration merely by tuning fundamental ferroelectric properties. Non‐monotonic dependence of the responsivity (RSC) on the ferroelectric polarization (P) is observed and at the optimal value of the film polarization, a more than three orders of magnitude increase in the RSC from the bulk BaTiO3 value is obtained, reaching RSC close to 10−2 A/W, the highest value reported to date for the archetypical ferroelectric BaTiO3 films. Our results challenge the applicability of standard first‐principles‐based descriptions of BPE to thin films and the inherent weakness of BPE in ferroelectric thin films.This article is protected by copyright. All rights reserved.

Depolarization Field-Induced Photovoltaic Effect in Graphene/α-In2Se3/Graphene Heterostructures

“…14 However, the wide band gap of many thin-film ferroelectrics in combination with the small short-circuit photocurrent density (J SC ) in the macroscale regime limits the utility of the FPVE compared to conventional photovoltaics. 10 In the ultrathin limit, when the channel length is reduced to tens of nm, the strength of the FPVE dramatically increases. [1][2][3]5 Generally, the FPVE originates from one of the three mechanisms: 15 rises in noncentrosymmetric materials due to an offset between the conduction and valence band states in real space.…”

“…The ferroelectric photovoltaic effect (FPVE)a photocurrent and photovoltage generated in ferroelectrics due to above band gap illuminationis a unique characteristic of ferroelectrics originating from the broken inversion symmetry of the crystal structure. − Unlike typical p–n junction photovoltaics, the carriers separate in the bulk of the material, and the open-circuit voltage ( V OC ) is not limited by the band gap. ,− Depending on the mechanism, power conversion efficiency (η) due to FPVE can exceed the Shockley–Queisser limit . However, the wide band gap of many thin-film ferroelectrics in combination with the small short-circuit photocurrent density ( J SC ) in the macroscale regime limits the utility of the FPVE compared to conventional photovoltaics . In the ultrathin limit, when the channel length is reduced to tens of nm, the strength of the FPVE dramatically increases. − , Generally, the FPVE originates from one of the three mechanisms: shift current, asymmetric Schottky barriers in the ferroelectric–electrode interface, and depolarization field.…”