Intrinsic open-circuit voltage and short-circuit current of ferroelectric photovoltaic effect
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Intrinsic open‑circuit voltage and short‑circuit current of ferroelectric photovoltaic effect Qiong Wu1,2 · Xin Wu1,2 · Shifeng Zhao1,2 Received: 16 July 2020 / Accepted: 12 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Photovoltaic effect of B iFeO3 (BFO) films prepared by sol–gel method was investigated. Both J–V curves with different polarization under illuminated conditions and the J–V curves with different polarization under dark conditions are measured. On this basis, this work provides a law that characterizes the intrinsic open-circuit voltage and short-circuit current density of BiFeO3 films by the differentials between illuminated and dark open-circuit voltage, as well as short-circuit current density. Furthermore, the components of open-circuit voltage are determined in detail. The practical conclusions show that it is accurate to use intrinsic open-circuit voltage and short-circuit current to reflect the strength of ferroelectric photovoltaic effect, not the values under illumination. Keywords Ferroelectric photovoltaic effect · J–V curves · Open-circuit voltage · Short-circuit current density
1 Introduction Ferroelectric photovoltaic effect (FPVE) has received extensive attention since its theoretic open-circuit voltage is free from the limitation of the bandgap, which is attributed to the fact that the mechanism of photovoltage is different from the traditional semiconductor p-n heterojunction [1, 2]. Many theories like domain wall theory, schottky-junction effect and depolarization field model have been put forward trying to explain the mechanism of FPVE. Importantly, all these theories are based on the viewpoint that FPVE is a bulk effect because photocurrent exists in the entire medium. For such bulk photovoltaic effect, the formation of photocurrent mainly includes three processes. Firstly, a number of photogenerated exciton pairs are produced when the ferroelectric films are illuminated by the light with the photon energy higher than the bandgap of the ferroelectric films. Then, these photogenerated exciton pairs are separated to form carriers by depolarization electric field (Edp) derived * Shifeng Zhao [email protected] 1
Inner Mongolia Key Lab of Nanoscience and Nanotechnology, Inner Mongolia University, Hohhot 010021, China
School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China
2
from the remanent polarization or built-in electric field (Ebi) derived from the schottky barrier [3]. Finally, carriers are collected on the electrodes. Thus, photocurrent is obtained. Therefore, J–V curves are usually measured on experiments to reflect the strength of FPVE. Generally, it is considered that the larger is the value of the illuminated open-circuit voltage (OCVi) and illuminated short-circuit current (SSCi), the better is the FEPV, and otherwise is opposite [4–6]. While the dark J–V curves of unpolarized samples was referred to characterize the illuminated open-circuit voltage and illuminated
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