Revealing the Impact of Phase Transition on N = 1 2D Perovskite Photodetectors With Intrinsically Tunable Narrowband Detection

Why It Matters

This breakthrough demonstrates that 2D perovskites can achieve ultra-high detectivity with intrinsic spectral selectivity, opening new avenues for compact, filter-free photodetectors. Understanding and controlling phase segregation is critical for translating these materials into reliable commercial sensors.

Key Takeaways

• n=1 2D perovskite photoconductors achieve 2.1×10^11 Jones detectivity.
• Halide mixing causes phase segregation, reducing device performance.
• PEACl additive suppresses segregation but adds trap states.
• Chloride promotes out-of-plane orientation, improving photodiode efficiency.
• Balancing structural order and electronic disorder is essential for performance.

Pulse Analysis

The emergence of n = 1 two‑dimensional perovskites has opened a new pathway for filter‑free narrowband photodetection. By confining a single layer of PbX6 octahedra between phenethylammonium (PEA) cations, these materials exhibit quantum‑confined absorption peaks that can be tuned across the visible spectrum. Compared with conventional three‑dimensional perovskites, the reduced dimensionality suppresses carrier diffusion, enabling intrinsically narrow spectral response without external optics. 1 × 10¹¹ Jones at 20 V underscores their competitive edge for compact imaging and spectroscopy.

However, the same halide alloying that provides wavelength tunability also triggers severe phase segregation, creating energetically disordered domains that quench photocurrent. Density‑functional theory calculations in the study reveal two distinct stacking orders that gradually convert as bromide is replaced by iodide, explaining the observed performance drop. Introducing a chloride source, PEACl, stabilizes the mixed‑halide lattice and forces out‑of‑plane orientation of the perovskite layers, but it simultaneously generates additional trap states that lower the photoconductor current.

The trade‑off highlights the delicate balance between structural uniformity and electronic purity. The findings have immediate relevance for the rapidly growing optoelectronic market, where narrowband detectors are sought for LiDAR, environmental monitoring, and biomedical imaging. By demonstrating that the additive improves photodiode performance while hampering photoconductor gain, the work points to device‑specific engineering strategies—favoring vertical charge extraction for diodes and minimizing traps for conductors. Future research will likely explore alternative halide‑blocking agents or strain‑engineered lattices to preserve long‑range order without sacrificing carrier mobility, paving the way for scalable, low‑cost 2D perovskite sensor arrays.