The study on novel ferroelectric photovoltaics

Abstract

The aim of this work was to search for novel ferroelectric photovoltaic materials The ferroelectric materials studied in this work were Bi0 5Na0 5TiO3 and CaFeSO because they haven’t been investigated thoroughly for the applications of interest Owing to a lack of carrier concentration ferroelectric materials usually have a very low conductivity below 10-8 S/cm which constrains the output power of ferroelectric photovoltaics In this study in order to increase the carrier concentration Bi0 5Na0 5TiO3 was doped with maganese ion Polycrystalline samples of Bi0 5Na0 5TiO3:Mn were prepared using the solid-state reaction method X-ray diffraction showed that pure phases of undoped and Mn doped Bi0 5Na0 5TiO3 could be obtained after sintering at 1100°C and 1000°C for 2 hours respectively The conductivity of Bi0 5Na0 5TiO3:5%Mn increased by two 2 orders of magnitude as compared with the undoped Bi0 5Na0 5TiO3 After poling the current-voltage curves of the samples were measured with and without light irradiation There was only a slight change in the output current before and after illumination for the undoped sample indicating a lack of photoexcited carriers However the output current increased with increases in the Mn content CaFeSO was not successfully synthesized using the solid-state reaction in this work; nevertheless two other compounds in this family Ca2Fe2S2O3 and Ca3Fe4S3O6 could be obtained by solid-state reaction under different conditions The measurement of resistivity and the Seebeck coefficient indicated that Ca2Fe2S2O3 is a p-type semiconductor and that Ca3Fe4S3O6 is an n-type semiconductor Neither Ca2Fe2S2O3 nor Ca3Fe4S3O6 produced photocurrent after illumination which was possibly due to an overly high recombination rate

Date of Award	2019
Original language	English
Supervisor	Xiao-Ding Qi (Supervisor)