Boosting Photovoltaic Output of Ferroelectric Ceramics by Optoelectric Control of Domains

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.