Dirac‐Source Linear X‐Ray Detection Diode

External readout electronics are optimally interfaced with X‐ray detection devices that exhibit linear current–voltage (IV) characteristics to enable direct signal acquisition with minimal analogue signal conditioning. This not only simplifies the analogue front‐end design but also enhances signal accuracy and system integration. Here, we present a Dirac source (DS) X‐ray detection diode that employs a monolayer graphene top electrode integrated into a perovskite‐based device architecture. In contrast to conventional devices with nonlinear, diode‐like IV responses, the DS source device displays a linear and stable IV behavior over an extended voltage range (200 V). This linearity arises from the unique Dirac dispersion and linear density of states intrinsic to graphene. The graphene interface also enables ultra‐low dark current densities (∼3 pA·cm − 2 at 1 V), approximately six orders of magnitude lower than those of standard metal‐contacted devices. A Schottky‐like barrier at the graphene/hole transport layer junction forms a back‐to‐back diode configuration, suppressing charge injection and minimizing leakage. Circuit‐level modelling and numerical simulations support this mechanism and validate the role of the interfacial design. This device design concept represents a robust strategy for developing low‐noise X‐ray detectors with minimal readout complexity, offering strong potential for advanced imaging and radiation monitoring technologies.