Drastically improved solar light absorbing ferroelectric thin film developed

A team of Korean scientists developed a method of combining ferroelectric thin film and a transition element, improving solar light absorption that creates more energy.

Ferroelectric: is a property of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field

Transition element: are any of various chemical elements that have valence electrons—i.e., electrons that can participate in the formation of chemical bonds—in two shells instead of only one.

The research was collaboration of GIST Professor Sanghan Lee, Gachon University Chung-Wung Park and PhD student Hyun-Ji An. They succeeded implementing ferroelectric thin film by adding Fe (iron) and Co (cobalt) into ferroelectric BLT reducing band gap and raising precision photoelectric.

Ferroelectric BLT: Lanthanum-doped bismuth titanate Bi3.25La 0.75Ti3O12 (BLT) is a material used to make ferroelectric film.

Bandgap: is an energy range in a solid where no electron states can exist. It determines conductivity of electrons.

Precision photoelectric: measurements of electric current value.

The research paper has been published with the Scientific Reports on June 17, 2016.

Improved photoelectric effect after Fe (iron) and Co (cobalt) added to BLT. (a) Co-doped BLT (Bi3.25La0.75Co1Ti2O12, BLCT) and Fe, Co-doped BLT (Bi3.25La0.75Fe0.25Co0.75Ti2O12, BLFCT) thin films showing the photocurrent density of BLCT is improved by 6 times relative to that of BLT and 25 times higher for BLFCT. (b) The schematic of the photocurrent measurement. The ITO (indium tin oxide) electrodes were deposited on the films, and photocurrent density (J) was measured between the two electrodes. (c) The schematic of the light wavelength range that the BLT, BLCT, and BLFCT films can absorb, which is predicted using the bandgap data.

The effect of doping on the overall electronic levels. The bandgap is due to the d-levels of the doped transition metal ions. One can see the bandgap being closer as Co and Fe being doped.

GIST Professor Sanghan Lee said, “Simply adding transition elements, such as Fe and Co improved solar light absorption without losing its spontaneous polarization characteristics, is expected to be an important milestone in developing the next generation optical devices, such as ferroelectric solar cell research.”