Non‐stoichiometric BZT‐BCT ferroelectrics with visible/near‐infrared photoresponse for broadband photodetection

Abstract

AbstractThe bulk photovoltaic effect in ferroelectric materials exhibits great potential in photoelectric applications. However, their photoresponse is generally limited to the UV region due to the wide bandgap feature of most perovskite ferroelectric materials, while the narrowing of bandgap is often accompanied by the degradation or even extinction of the ferroelectric polarization. Herein, 0.5Ba(Zr0.2Ti0.8)O3‐0.5(Ba0.7Ca0.3)TiO3 (BZT‐BCT) with bandgap of 2.4 eV arising from the existence of Ti3+ is prepared, and then titanium vacancies are introduced to BZT‐BCT ferroelectric solid solutions through B‐site off‐stoichiometry (0.5Ba(Zr0.2Ti0.8)O3‐0.5(Ba0.7Ca0.3)Ti1 − x%O3, BZT‐BCT1 − x%) to further tune the bandgap. Lowest bandgap of 2.1 eV with near‐infrared (NIR) absorption is obtained for BZT‐BCT0.990 composition. Moreover, both the ferroelectricity and piezoelectricity (Pr = 14.3 μC/cm2, d33 = 415 pC/N) are well maintained after mitigating the effect of the increased oxygen vacancies associated with Ti‐deficiency on the spontaneous polarization by oxygen‐annealing treatment. More specifically, the oxygen‐annealing BZT‐BCT0.985 composition, showing at least 2.4‐fold photovoltage and 2.2‐fold photocurrent of the pristine BZT‐BCT ceramic, exhibits excellent transient pyroelectric current and stable photovoltaic current under xenon, NIR, and monochromatic visible lights. The photoelectric device based on the oxygen‐annealing BZT‐BCT0.985 ceramic performs wide‐spectrum photodetection properties from 405 nm light to NIR light, which makes it a potential candidate for self‐powered photodetector applications.