Boosted Responsivity and Tunable Spectral Response in B‐Site Substituted 2D Ca<sub>2</sub>Nb<sub>3−</sub><i><sub>x</sub></i>Ta<i><sub>x</sub></i>O<sub>10</sub> Perovskite Photodetectors
Xinya Liu, Siyuan Li, Ziqing Li, Yong Zhang, Wei Yang, Ziliang Li, Hui Liu, Dmitry V. Shtansky, Xiaosheng Fang
Abstract
Abstract 2D Dion‐Jacobson perovskite oxides, featuring fascinating optical and electric properties, exhibit great potential in optoelectronic devices. However, the device sensitivity and spectral selectivity are limited. Herein, B‐site substituted calcium niobate Ca 2 Nb 3− x Ta x O 10 ( x = 0, 0.5, 1, 1.5) nanosheets are prepared by liquid exfoliation. The photodetectors (PDs) based on these nanosheets exhibit tunable spectral response by tailoring the band gap of the nanosheets. All the Ta‐substituted PDs show increased photocurrent and enhanced responsivity, among which the Ca 2 Nb 2.5 Ta 0.5 O 10 PD exhibits the optimal performance with a photocurrent of 31.4 µA, a high on–off ratio of 5.6 × 10 4 and a boosted responsivity of 469.5 A W −1 at 1.0 V toward 295 nm, which is over 7000‐fold higher than that of pristine Ca 2 Nb 3 O 10 PD. It is proposed that the significantly optimized responsivity is ascribed to the enhanced photoconductive gain that mainly originates from the introduction of the trap states by the B‐site substitution. Nevertheless, excess substitution is detrimental to the responsivity and the response speed. This work demonstrates that the rational control of B‐site substitution tailors the band gap and modulates the charge‐carrier behaviors in 2D perovskite oxides, which provides an effective avenue for achieving high‐performance PDs with tunable spectral response and excellent responsivity.