Electron−hole separation in ferroelectric oxides for efficient photovoltaic responses

Abstract

SignificancePhotovoltaics (PVs) benefitting from ferroelectric polarizations can overcome critical limitations of conventional type PVs. In this class, Bi2FeCrO6 is known to be the best-performing material; however, a fundamental understanding of the origin is lacking, which has limited further performance improvements. Here, we carried out a theoretical investigation of the electronic structure of this material. As a result, electron−hole (e-h) pairs are observed to separate upon photoexcitation, which can be a dominant underlying mechanism for the exceptional PV responses. Based on this understanding, we further suggest five novel materials that can offer a combination of strong e-h separations and visible-light absorptions. We expect the community of ferroelectric PVs to immediately benefit from the features of the new suggested materials.

Towards photoferroic materials by design: recent progress and perspectives

“…The high efficiency of BFCO solar cells was ascribed to their narrow direct band gap, which enhances light absorption. First-principles calculations have suggested that the excellent performance also lies in a more efficient separation of the e-h pairs, which are spatially separated on the Fe and Cr sites [34]. Transition metals (TM), in particular Mn-doped BFO, have also been investigated and have been demonstrated to improve the photoferroic properties of BFO [35].…”

Organic enantiomeric high- T c ferroelectrics

“…As an important subject of ferroelectrics in classical physics, it is of great potential to incorporate the homochirality to ferroelectricity to broaden much more fascinating applications. History has shown such interesting relevance between homochirality and ferroelectrics that the first ferroelectric discovered in 1920, i.e., Rochelle salt ([KNaC 4 H 4 O 6 ]·4H 2 O), is a homochiral metal coordination compound (22), known as the first molecular ferroelectric crystal being optically active, while inorganic ferroelectrics, currently dominating in both academic research and industrial manufacture due to their practical applications in memory elements, capacitors, piezoelectric actuators, and sensors, do not have homochiral centers, leading to significant lagging in the strong correlation between homochirality and ferroelectrics (23,24).…”

Strain-attenuated spin frustration in double perovskite Sr2FeOsO6

“…and O 2p states, whereas the conduction band edge is almost entirely due to Fe 3d states. As a consequence, photoexcitation will lead to a spatial electron-hole separation between the Fe (conduction band minimum) and Os (valence band maximum) sublattices, similar to Bi 2 FeCrO 6 [35], implying that the electron-hole transition matrix element and thus the electron-hole recombination rate are small, which is desirable for photovoltaics. Based on the frequency-dependent complex dielectric function, we obtain for Sr 2 FeOsO 6 an outstanding spectroscopic limited maximum efficiency [36] of 32%, outperforming even the prototypical perovskite solar cell material MAPbI 3 (MA = methylammonium; 31%).…”