Synthesis of single-unit-cell-thick perovskites by liquid-phase confined assembly for high-performance ultrastable X-ray detectors

The instability of halide perovskites under working conditions or during complex postprocessing is challenging for practical applications. Here we developed a room-temperature, two-phase assembling strategy to synthesize single-unit-cell perovskite chains within single-walled carbon nanotubes (SWCNTs). This approach is efficient, scalable and tailorable, and can be used to assemble a range of single-chain perovskites. The single-unit-cell-chain perovskites show unconventional stoichiometries (such as [Cs4PbI5]+) due to dimensionality reduction and are balanced by negatively charged nanotubes. A direct X-ray detector constructed with high-entropy-Cs3MCl6@SWCNT exhibits outstanding performance, with a high sensitivity of $$1.22\times10^{4}\,\upmu{\mathrm{C}}\,{\mathrm{Gy}}_{\mathrm{air}}^{-1}\,{\mathrm{cm}}^{-2}$$ , a low dark current density of 0.2 nA cm−2, a negligible dark current drift of 8.5 × 10−7 nA cm−1 s−1 V−1 and a superior detection limit of 16.6 nGyair s−1. These surpass various common semiconductor and state-of-the-art perovskite detectors due to the ionic character of perovskite@SWCNT inducing a strong cation–π interaction, suppressing ion migration. The device is stable under harsh conditions, including continuous X-ray irradiation, high temperatures, exposure to ambient air for 91 days and immersion for 96 h in water. This low-cost synthetic methodology paves the way for the commercialization of potential perovskite X-ray detectors for medical and industrial applications. A two-phase assembly approach is developed to synthesize single-unit-cell-thick perovskite chains within single-walled carbon nanotubes. A direct X-ray detector constructed with the confined perovskite chains exhibits outstanding performance and ultrahigh stability under harsh conditions.