Ferroelectric Oxides for Solar Energy Conversion, Multi‐Source Energy Harvesting/Sensing, and Opto‐Ferroelectric Applications

Abstract

Photoferroelectrics belong to a unique material family that exhibits both photovoltaic and ferroelectric effects simultaneously. The photovoltaic effect is the only known direct method of converting light into electricity and is the basis of solar cells. The ferroelectric effect can induce piezoelectric and pyroelectric effects, which are the working principles of widely used kinetic and thermal sensors, transducers, actuators, and energy harvesters. For a long time, photoferroelectric research was restricted to theoretical investigations only because of either the wide band gap ( E g ), which is not able to effectively absorb visible light, or to the weak ferroelectricity caused by a narrow E g . Recent scientific breakthroughs, however, have opened doors for the development of practical applications. In this article, emerging concepts of creating balanced photovoltaic and ferroelectric properties for photoferroelectrics, as well as those of novel applications in future devices, are presented.

A Single‐Material Multi‐Source Energy Harvester, Multifunctional Sensor, and Integrated Harvester–Sensor System—Demonstration of Concept

“…The concept of using one material for multiple tasks proposed in the authors' previous works (either harvesting or sensing or both) is further elaborated here with a practical device responding to different energy sources equivalent to realistic conditions. [2,57] The presented results are also expected to inspire further advances in relevant works in materials, systems, and circuitry. For instance, the triple-source energy conversion in this work makes a leap in the singlematerial device design from previously reported dual-source counterparts such as the use of ZnO for simultaneous piezoelectric and thermoelectric effects to harvest kinetic and thermal energy.…”

“…[54] A potentially effective method to improve the energy conversion efficiencies or capabilities of the piezoelectric and photovoltaic effects simultaneously would be to fabricate single crystals or highly oriented thin films of KNBNNO. [57] In this work, the KNBNNO was a ceramic in which randomly oriented grains may hinder complete poling and thus suppress piezoelectricity, whereas the large number of grain boundaries may accelerate charger carrier recombination and hence degrade the PEC. [39,57,58]…”

“…[57] In this work, the KNBNNO was a ceramic in which randomly oriented grains may hinder complete poling and thus suppress piezoelectricity, whereas the large number of grain boundaries may accelerate charger carrier recombination and hence degrade the PEC. [39,57,58]…”

A Simulation Model for Narrow Band Gap Ferroelectric Materials

“…The ferroelectric version of the Jiles-Atherton model, as proposed in reference, [20] provides the evolution of P as a function of E. It gives relatively accurate results but constrains experimental conditions. It requires (1) low frequency (f < 1 Hz, quasi-static state) and (2) collinearity of P and E. In this model, P is composed from both its reversible and irreversible constitutes, defined by Equation (1) where c is the polarization reversibility coefficient and P an is the anhysteretic polarization. P an is a sigmoid function of E which can be expressed from a Langevin-type function shown as Equation (2).…”

“…Photoferroelectrics are ferroelectric materials exhibiting photovoltaic effect at the same time. [1] Conventional and widely known ferroelectrics like PZT (Pb(Ti, Zr)O 3 ) and BaTiO 3 are the most studied photoferroelectrics. [2] These materials have been extensively used as kinetic and thermal sensors, actuators, transducers, and energy harvesters thanks to their excellent Photoferroelectric KNBNNO, as mentioned above, is a perovskite-structured, narrow band gap ferroelectric material.…”