To get the 1000x figure, the research is comparing photocurrents from bulk BTO and their special crystal-aligned BTO at a specific wavelength of incident light (306nm).

They also compare photocurrents under a solar simulator and achieve 100x increase vs bulk BTO.

At no point do they make comparison to state of the art BTO cells, which almost certainly aren't just bulk BTO but are likely doped, nanostructured, or have some other novelty.