Broadband Pyro-Phototronic Effect in Lead-Free Double Perovskite Crystal Enables UV-to-NIR and Polarization-Sensitive Detection

Broadband
spectral detection holds a significant promise
for diverse
applications in environmental monitoring, infrared sensing, and biomedicine.
However, the photoresponsive ranges of most photoactive materials
are often limited by the intrinsic optical bandgap, which predominantly
focuses on the ultraviolet and visible spectral region, thus hindering
their broadband optical applications. Therefore, achieving high-performance
broadband spectral photodetection is essential for advancing various
cutting-edge technologies. In this study, we have obtained a lead-free
double perovskite (FPEA)4AgBiI8 (1, FPEA+ is p-fluorophenethylammonium),
which has strong structural polarity and a narrow bandgap (Eg) of ∼1.80 eV. The π–π
stacking of interlayer FPEA+ cations creates a robust interlayer
connection that contributes to the growth of high-quality single crystals.
Notably, the inherent polarity of 1 allows a broadband
pyro-phototronic effect that covers a wide spectral range from the
ultraviolet (UV, 377 nm) to the near-infrared (NIR, 2000 nm) region,
breaking the limitation of its optical bandgap. This unique pyro-phototronic
effect significantly enhances the photoelectric performance of 1, of which the photopyroelectric peak current at 637 nm illumination
is 427% larger than the photovoltaic current. Additionally, combining
the advantages of structural anisotropy and pyro-phototronic effect,
the crystal-based device of 1 creates superior polarization-sensitive
photodetection behaviors. This study not only enriches the portfolio
of photoactive perovskite candidates but also provides an effective
strategy for assembling high-performance optoelectronic devices.