Enhancement of photovoltage by electronic structure evolution in multiferroic Mn-doped BiFeO3 thin films

Abstract

The bulk photovoltaic effect (BPVE) is a mechanism of recent focus for novel solar cells that exceed the power conversion efficiency of p–n junction solar cells because of the quantum mechanical effect to generate photocurrent known as shift current. Ferroelectrics are receiving attention again because of their high voltage generation by the BPVE and converse piezoelectric effect to realize high performance optical actuators. We have investigated the BPVE in ferroelectric BiFeO3 (BFO) single crystal thin films, whereby the photovoltage was enhanced by Mn doping, and 852 V generation was demonstrated at 80 K. The enhancement mechanism was also investigated using soft and hard X-ray photoelectron spectroscopy (SXPES, HAXPES), and soft X-ray absorption spectroscopy with synchrotron radiation. This report reveals a way to new voltage source applications employing the BPVE for high impedance devices with ferroelectrics. Important aspects for designing ferroelectric materials by impurity doping are also discussed.

A Type‐II Heterostructure with a KBiFe2O5 Brownmillerite Core and a ZnO Nanoparticle Shell for Enhanced Optoelectronic Performance

“…[6][7][8][9] In this context, oxide-based multiferroic perovskite materials where both Currie and Neel temperatures are above room temperature respond well to photons due to their large internal electric field. [10,11] BiFeO 3 is a well-known multiferroic that has attracted the attention of ferroelectric photovoltaics by producing high photovoltage up to 15 V. [10,12,13] In addition to the potential magnetoelectric and photovoltaic applications, BiFeO 3 is also used as photocatalytic material to degrade industrial dyes owing to their visible light response. [14][15][16][17][18] However, due to their large bandgap (> 2.2 eV) and poor conductivity they are not superior materials for optoelectronics applications.…”

Impact of film thickness on the external quantum efficiency of bulk photovoltaic effects in Mn-doped BiFeO3 thin films

“…In particular, the bulk photovoltaic effect (BPVE) has attracted significant attention because this effect can result in above-bandgap open-circuit voltage (V OC ) values. [16][17][18][19][20][21][22][23] In conventional solar cells based on p-n junctions, electronhole pairs generated by exposure to light are separated by the internal electric field at the junction depletion layer, meaning that V OC is limited by the energy of the bandgap, E g . Thus, producing above-bandgap V OC values is of interest.…”

Switchable ferroelectric photovoltaic response in Sc0.2Al0.8N-based optoelectronic devices

“…3) Primarily, different from traditional p-n junction with photovoltaic effect determined by the quasi-Fermi energy, FePV materials could separate photogenerated electron-hole pairs through its internal depolarization electric field, which makes its open circuit voltage (V OC ) much larger than optical bandgap. [4][5][6] Moreover, its short circuit photocurrent density (J SC ) can be regulated by switching the non-volatile polarization states. 7,8) This means that the ferroelectric polarization of the material can be changed by applying an external electric field pulse to write the information of electrical signal in and the information could be read out by testing J SC under light illumination, therefore realizing electrical writing and optical reading.…”