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A recent publication on single crystals of two-dimensional, layered organic–inorganic (BA)₂CsAgBiBr₇ double perovskite (BA⁺ = <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>H</mi><mn>3</mn></msub><msub><mrow><mfenced><mrow><mi>C</mi><msub><mi>H</mi><mn>2</mn></msub></mrow></mfenced></mrow><mn>3</mn></msub><mi>N</mi><msubsup><mi>H</mi><mn>3</mn><mo>+</mo></msubsup></mrow></semantics></math></inline-formula>) suggested the great potential of this semiconductor material in the detection of X-ray radiation. Our powder XRD measurement confirms the crystallinity and purity of all samples that crystallise in the monoclinic space group <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><msub><mn>2</mn><mn>1</mn></msub><mo>/</mo><mi>m</mi></mrow></semantics></math></inline-formula>, while the single crystal XRD measurements reveal the dominant {001} lattice planes. The structure–property relationship is reflected in the lower resistivity values determined from the van der Pauw measurements (1.65–9.16 × 10¹⁰ Ωcm) compared to those determined from the IV measurements (4.19 × 10¹¹–2.67 × 10¹² Ωcm). The density of trap states and charge-carrier mobilities, which are determined from the IV measurements, are 1.12–1.76 × 10¹¹ cm^–3 and 10⁻⁵–10⁻⁴ cm²V^–1s^–1, respectively. The X-ray photoresponse measurements indicate that the (BA)₂CsAgBiBr₇ samples synthesised in this study satisfy the requirements for radiation sensors. Further advances in crystal growth are required to reduce the density of defects and improve the performance of single crystals.