Boosting Photovoltaic Output of Ferroelectric Ceramics by Optoelectric Control of Domains

Abstract

Photo‐ferroelectric single crystals and highly oriented thin‐films have been extensively researched recently, with increasing photovoltaic energy conversion efficiency (from 0.5% up to 8.1%) achieved. Rare attention has been paid to polycrystalline ceramics, potentially due to their negligible efficiency. However, ceramics offer simple and cost‐effective fabrication routes and stable performance compared to single crystals and thin‐films. Therefore, a significantly increased efficiency of photo‐ferroelectric ceramics contributes toward widened application areas for photo‐ferroelectrics, e.g., multisource energy harvesting. Here, all‐optical domain control under illumination, visible‐range light‐tunable photodiode/transistor phenomena and optoelectrically tunable photovoltaic properties are demonstrated, using a recently discovered photo‐ferroelectric ceramic (K0.49Na0.49Ba0.02)(Nb0.99Ni0.01)O2.995. For this monolithic material, tuning of the electric conductivity independent of the ferroelectricity is achieved, which previously could only be achieved in organic phase‐separate blends. Guided by these discoveries, a boost of five orders of magnitude in the photovoltaic output power and energy conversion efficiency is achieved via optical and electrical control of ferroelectric domains in an energy‐harvesting circuit. These results provide a potentially supplementary approach and knowledge for other photo‐ferroelectrics to further boost their efficiency for energy‐efficient circuitry designs and enable the development of a wide range of optoelectronic devices.

Optical Control of Ferroelectric Domains: Nanoscale Insight into Macroscopic Observations

“…In this context, Bai et al synthesized a novel band‐gap (1.6 eV down from >4 eV) engineered lead‐free ferroelectric composition, i.e. (K 0.5 Na 0.5 )NbO 3 –2 mol% Ba(Ni 0.5 Nb 0.5 )O 3− δ (KNBNNO or KNN‐BNNO), and demonstrated multiple functionalities (piezoelectric, pyroelectric, and photovoltaic effects) and their cumulative effect using this single material . (K 0.5 Na 0.5 )NbO 3 supports off‐center distortion and is responsible for ferroelectric nature of KNN‐BNNO while Ba(Ni 0.5 Nb 0.5 )O 3− δ controls the electronic states in the gap of parent (K 0.5 Na 0.5 )NbO 3 using oxygen vacancies and Ni +2 ions .…”

Mutual Insight on Ferroelectrics and Hybrid Halide Perovskites: A Platform for Future Multifunctional Energy Conversion

“…However, at the same time, there is a possibility of a light‐induced capacitance increase using appropriate device configuration . Several reports suggest that the dielectric constant of some ferroelectrics is sensitive to light which puts them forward for photocapacitor application. Intriguingly, a photocapacitor based on ferroelectrics will have a simple device architecture (a parallel plate capacitor with transparent electrodes) in contrast to hybrid halide perovskites because light could directly change the state of polarization in ferroelectrics.…”

“…The energy conversion through an Olsen cycle could be equally feasible for non‐ferroelectric materials where a change in electrical properties, such as permittivity/conductivity, could be observed with thermal fluctuations, mechanical vibrations or light . In such cases, the temperature/stress/light‐dependent electrical response could be utilized along with the applied electric field in a cyclic fashion.…”

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

“…The core functional material for multi-source energy conversion has been developed and reported in the authors' previous works. [36][37][38] It is a perovskite-structured ceramic material of (K 0.5 Na 0.5 )NbO 3 (KNN) doped with 2 mol% Ba(Ni 0.5 Nb 0.5 )O 3-Δ (BNNO). This material is abbreviated to KNBNNO hereinafter.…”