Chemical Potential Diagram Guided Rational Tuning of Electrical Properties: A Case Study of CsPbBr₃ for X‐ray Detection

Abstract Controlling the carrier polarity and concentration underlies most electronic and optoelectronic devices. However, for the intensively studied lead halide perovskites, the doping tunability is inefficient. In this work, taking CsPbBr₃ as an example, it is revealed that the coexistence of metallic Pb or CsBr₃/Br₂, rather than the precursor ratio, can provide Pb‐rich/Br‐poor or Br‐rich/Pb‐poor chemical conditions, enabling the tunability of electrical properties from weak n‐type, intrinsic, to moderate p‐type. Experimentally, under Br₂‐exposure treatment, a shift of the Fermi level as large as 1.00 eV is achieved, which is one of the highest value among all kinds of doping methods. The X‐ray detector based on the intrinsic CsPbBr₃ exhibits excellent performance, with a negligible dark‐current drift of 7.1 × 10⁻⁴ nA cm⁻¹ s⁻¹ V⁻¹, a low detection limit of 103.6 nGy_air s⁻¹, and a high sensitivity of 9085 μC Gy_air⁻¹ cm⁻². This work provides a critical understanding and guidance for tuning the electrical properties of lead halide perovskites, which establishes good foundations for achieving intrinsic perovskite semiconductors and also constructing potential homojunction devices.