Band Gap of Pb(Fe0.5Nb0.5)O3 Thin Films Prepared by Pulsed Laser Deposition

Abstract

Ferroelectric materials have gained high interest for photovoltaic applications due to their open-circuit voltage not being limited to the band gap of the material. In the past, different lead-based ferroelectric perovskite thin films such as Pb(Zr,Ti)O3 (Pb,La)(Zr,Ti)O3 and PbTiO3 were investigated with respect to their photovoltaic efficiency. Nevertheless, due to their high band gaps they only absorb photons in the UV spectral range. The well-known ferroelectric PbFe0.5Nb0.5O3 (PFN), which is in a structure similar to the other three, has not been considered as a possible candidate until now. We found that the band gap of PFN is around 2.75 eV and that the conductivity can be increased from 23 S/µm to 35 S/µm during illumination. The relatively low band gap value makes PFN a promising candidate as an absorber material.

Narrow Bandgap Inorganic Ferroelectric Thin Film Materials

“…Representative ones are solar cells, [50] ultraviolet detectors, [22] pyroelectric infrared detectors, actuators, [34] which are one of the frontiers and hotspots of high-tech research at present. [27][28][55][56][57] Narrow bandgap inorganic ferroelectric films are classified into the following three categories according to the microstructure of the material: single crystal films, polycrystalline films, and composite films. In Table 1, we summarize the representative highly oriented single crystal thin film materials, polycrystalline materials, and composite thin film materials in recent years.…”

“…Representative ones are solar cells, [ 50 ] ultraviolet detectors, [ 22 ] pyroelectric infrared detectors, actuators, [ 34 ] which are one of the frontiers and hotspots of high‐tech research at present. [ 27–28,55–57 ]…”

“…Ferroelectric materials are generally considered to be wide bandgap semiconductors with bandgaps between 3.0 and 3.8 eV, [24][25][26][27][28][29] and their low absorption coefficient and photocurrent density limit the photovoltaic applications of ferroelectric materials. [30] As shown in Figure 1, photovoltaic materials with a bandgap of 1.0-1.8 eV can absorb the solar spectrum with maximum efficiency (Figure 1a,b), [31] and hexagonal ferrites (h-RFOs) with a narrow bandgap (1.1-2.0 eV) can absorb light in a very wide range of wavelengths (Figure 1c,d).…”