Researchers from the University of Barcelona, Jaume I University, Slovak University of Technology and University of Valencia have engineered ultrasensitive photodetectors based on inkjet-printed nanocrystalline films of mixed-phase “raisin bread” CsPbBr₃/Cs₄PbBr₆ perovskite integrated onto graphene. By embedding photoactive CsPbBr₃ nanocrystals within a wider-bandgap Cs₄PbBr₆ matrix, the team creates a composite architecture that enhances charge confinement while simultaneously improving environmental stability relative to conventional perovskite films.
The raisin-bread morphology plays a central role in suppressing non-radiative recombination and mitigating degradation pathways that typically limit metal-halide perovskites in photodetector operation. In this configuration, the Cs₄PbBr₆ host passivates the surface of CsPbBr₃ nanodomains and acts as a protective scaffold, helping preserve optoelectronic properties over extended operation under ambient conditions. Coupled with solution-based inkjet deposition, this strategy demonstrates that complex phase-engineered perovskite microstructures can be reproducibly formed over large areas in a maskless, vacuum-free process, supporting low-cost, scalable manufacturing.
When integrated with graphene, these mixed-phase perovskite films deliver exceptional device figures of merit, with responsivities surpassing 5.7 × 10⁴ A W⁻¹ and specific detectivities above 10¹⁶ Jones at 312 nm in the UV region. The perovskite functions as a highly efficient photoconductive absorber that generates and stores photocarriers, while the adjacent graphene channel rapidly drains these carriers, strongly amplifying the photocurrent through a photogating mechanism. This interplay yields broadband charge transport and high gain, enabling the detection of extremely weak optical signals across a wide spectral window.
Beyond raw sensitivity, the devices exhibit remarkable operational stability, maintaining performance over prolonged exposure thanks to the robust all-inorganic perovskite composition and the encapsulating effect of the Cs₄PbBr₆ matrix. The authors highlight that this longevity is primarily rooted in the composite raisin-bread architecture, which resists ion migration and moisture-induced degradation that plague many perovskite systems. Altogether, the work showcases a scalable, sustainable route to high-performance broadband photodetectors, underscoring how judicious phase engineering in cesium lead bromide perovskites can unlock new application spaces in perovskite optoelectronics.
