Recently the solar energy, an inevitable part of green energy source, has become a mandatory topics in frontier research areas. In this respect, non-centrosymmetric ferroelectric perovskites with open circuit voltage (V OC) higher than the bandgap, gain tremendous importance as next generation photovoltaic materials. Here a non-toxic co-doped Ba1-x (Bi0.5Li0.5) x TiO3 ferroelectric system is designed where the dopants influence the band topology in order to enhance the photovoltaic effect. In particular, at the optimal doping concentration (x opt ~ 0.125) the sample reveals a remarkably high photogenerated field E OC = 320 V/cm (V OC = 16 V), highest ever reported in any bulk polycrystalline non-centrosymmetric systems. The band structure, examined through DFT calculations, suggests that the shift current mechanism is key to explain the large enhancement in photovoltaic effect in this family. © 2018 The Author(s).

Birabar Ranjit Kumar Nanda

Department Of Physics

P. Murugavel

Subhajit Pal

Atal Bihari Swain

Arnab Pal

article

calculation

Doping

energy resource

Solar energy

Fulltext

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

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IIT Madras

Scientific Reports

The photovoltaic (PV) properties of polycrystalline Bi1-xLaxFeO3 (x = 0-0.3) films have been explored. The X-ray diffraction study reveals that there is a gradual phase transition with the increase in La doping. The composition x = 0.25 is found to be the morphotropic phase boundary (MPB), beyond which the system turns into the non-/antipolar orthorhombic phase. The polarization measurements reveal improved ferroelectric properties with the maximum remanent polarization observed for the x = 0.25 film. A systematic study on the direct and indirect bandgaps of the films has shown a decreasing trend with composition. Interestingly, the PV studies exhibit a maximum open-circuit voltage of 1.30 V for the x = 0.25 film which is three times larger than the value observed for pure BiFeO3 (BFO) (0.47 V). The enhanced PV response in La-doped BFO correlates with the polarization and the change in direct/indirect bandgaps associated with structural instability near the MPB composition. The approach used in this work for enhancing the PV performance in ferroelectric BFO through the combined effects of polarization, bandgaps and competing structures provides a better pathway for improving the ferroelectric PV effect. © 2019 Author(s).

Applied Physics Letters

Large photovoltaic response in rare-earth doped BiFeO3 polycrystalline thin films near morphotropic phase boundary composition

Ferroelectrics are considered next generation photovoltaic (PV) materials. In this work, a switchable and large PV effect is demonstrated in a Pb-free ferroelectric 0.5Ba(Zr 0.2 Ti 0.8 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 (BZT-BCT) thin film fabricated by a pulsed laser deposition technique. The material shows a remarkable PV output of 0.81 V due to its morphotropic phase boundary composition. The observed PV effect is analyzed on the basis of the interfacial Schottky barrier and bulk depolarization field. The poling dependent PV studies revealed that although the Schottky and depolarization field contribute to the PV effect, the latter dominates the PV response beyond the coercive field. Additionally, the importance of this compound in the field of a self-biased photodetector is elucidated in terms of calculated photodetector parameters such as responsivity and detectivity. The explored results will bring significant advancement in the field of ferroelectric PV, UV solid state detector applications and also give an additional dimension to the multifunctional ability of the BZT-BCT system. © 2019 Author(s).

APL Materials

Polarization controlled photovoltaic and self-powered photodetector characteristics in Pb-free ferroelectric thin film

The electrical poling of piezoceramics is an essential process, to maximize their piezocoefficient prior to applications, which can significantly alter their other physical properties. In this study, the effect of poling on the properties of lead free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 exhibiting large piezocoefficient was investigated. The sample revealed octahedral distortion induced structural transformation upon poling. The impedance spectrum displayed the resonance modes in poled state, where maximum power transmission is feasible. The polarization hysteresis loop exhibited an asymmetry with an internal bias electric field of 41 V/mm due to the field induced orientational defect. The strain measurements revealed 50% enhancement in electrostriction for the sample after poling. Additionally, the sample revealed an incremental change in bandgap due to B-site cationic off-centre displacements induced by the octahedral distortion. Importantly, the poling induced large internal bias field and the near UV bandgap of the sample facilitated the observed large photovoltaic response with giant open circuit voltage of 18 V which could open up an additional application in the fields such as photovoltaic and UV detector for this versatile compound. © 2019 Elsevier B.V.

Journal of Alloys and Compounds

Influence of external electric field on the physical characteristics of lead free BZT- BCT piezoceramic

The polycrystalline (Bi1−xSrx)(Fe1−xTix)O3 (x = 0.0, 0.05, 0.10, and 0.20) thin films were grown on Pt(111)/TiO2/SiO2/Si(100) substrates using chemical solution deposition technique. X-ray diffraction pattern revealed that pure BiFeO3 film is crystallized in rhombohedrally distorted crystal structure. However, the patterns for doped samples displayed a mixed-phase (rhombohedral + tetragonal) structure. The Raman studies revealed the emergence of B mode related to the tetragonal phase along with the modes corresponding to the rhombohedral phase in doped systems. The photovoltaic studies displayed a large photovoltaic response for the parent compound with an open-circuit voltage of 0.47 V. However, it showed a decrease in the photovoltaic response with an increase in composition x. The composition-dependent photovoltaic response could be correlated to the evolution of tetragonal phase fractions and the polarization. Additionally, the poling-dependent photovoltaic studies revealed the dominant role played by the polarization in comparison with the interface Schottky effect. This work gives an improved understanding of the ferroelectric photovoltaic mechanism and, therefore, may offer guidelines to design and optimize photovoltaic materials. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

Journal of Materials Science: Materials in Electronics

The composition and poling-dependent photovoltaic studies in ferroelectric (Bi1−xSrx)(Fe1−xTix)O3 thin films

The photovoltaic effect in noncentrosymmetric ferroelectrics is gaining much research interest due to its remarkable above band-gap photovoltage. Among the available ferroelectric systems, the 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 with its high piezocoefficient is considered as an attractive lead-free multifunctional ferroelectric material. The photovoltaic studies on this compound reveal the discovery of a large photogenerated electric field of 368Vcm-1, one of the highest values reported in polycrystalline ferroelectric systems. It is demonstrated that the large photovoltaic response in this ferroelectric system is due to the symmetry breaking structural transformation from the tetragonal to rhombohedral and orthorhombic phases. Density functional calculations show that this symmetry breaking transformation leads to the reduction of electron and hole effective masses and delocalization and reorientation of the conduction charge cloud along the polarization direction, which, in turn, gives a high photovoltaic response. © 2019 American Physical Society.

Physical Review Applied

Large Bulk Photovoltaic Response by Symmetry-Breaking Structural Transformation in Ferroelectric [Ba (Zr0.2Ti0.8) O3] 0.5[(Ba0.7Ca0.3)Ti O3] 0.5

Giant photovoltaic response in band engineered ferroelectric perovskite

Nature Communications

Shift current photovoltaic effect in a ferroelectric charge-transfer complex

Nature Reviews Materials

Understanding the physical properties of hybrid perovskites for photovoltaic applications

Remarkably enhanced photovoltaic effects and first-principles calculations in neodymium doped BiFeO3

Physical Review Letters

Mesoscopic Free Path of Nonthermalized Photogenerated Carriers in a Ferroelectric Insulator

Journal	Scientific Reports
Publisher	Nature Publishing Group
ISSN	20452322
Open Access	No