Realizing low-ion-migration and highly sensitive X-ray detection by building g-C3N4 and CH3NH3PbI3 bulk heterojunction pellets

Abstract

Three-electronic-dimensional (3D) lead halide perovskites show high X-ray sensitivities and a low limit of detection. However, servere ion migration causes dark current drift and worsens long-term operational stability. Although two-electronic-dimensional (2D) perovskite and 3D perovskite heterojunction devices have been shown to reduce ion migration, their current responses to X-rays have decreased considerably. A device with low ion migration without sacrificing X-ray sensitivity is needed. Atomic-thick two-dimensional (2D) materials with small pore sizes between atoms and high carrier-tunneling possibilities through them are reasonable candidates to simultaneously block ion migration and retain carrier–transport properties. Herein, a 2D monolayer of g-C₃N₄ was introduced into a CH₃NH₃PbI₃ (MAPbI₃) polycrystalline pellet through hot pressing. The small-sized tri-s-triazine structure of g-C₃N₄ could inhibit ion migration without affecting the electron transport of the perovskite pellet. As a result, the g-C₃N₄/MAPbI₃ heterojunction pellet exhibited an ultra-low current drift of 4.87 × 10⁻⁵ nA cm⁻¹ s⁻¹ V⁻¹ at an electric field of 12.66 V mm⁻¹. Simultaneously, the detector exhibited a high sensitivity of 1.78 × 10⁵ μC Gy_air⁻¹ cm⁻² under 75.95 V mm⁻¹ and a low limit of detection of 27 nGy_air s⁻¹ under 12.66 V mm⁻¹, which are among the best of reported results. This work provides an effective design strategy to develop X-ray detectors with low ion migration and high detection performance.