Researchers have sharply increased the sensitivity and speed of quasi-2D perovskite photodetectors by carefully tuning how they interact with silver plasmonic nanostructures, according to a new study in Small.
Study: Boosting Photodetection via Plasmonic Coupling in Quasi-2D Mixed-n Ruddlesden-Popper Perovskite Nanostripes. Image Credit: Foto-Ruhrgebiet/Shutterstock.com
Metal halide perovskites are attractive for their use in low-cost, high-performance photodetectors, but their efficiency is often limited by how effectively they harvest and convert light.
One strategy is to pair them with plasmonic metal nanostructures, which support surface plasmons and localized surface plasmon resonances (LSPR).
These resonances confine light into very small volumes and create intense local electric fields near the metal surface. That can increase light absorption in nearby perovskite, while plasmon decay can drive hot electron injection (HEI) and non-radiative energy transfer processes such as plasmon-induced resonance energy transfer (PIRET).
However, the benefit depends on how strongly the plasmons couple to excitons in the perovskite, and on the quality of the interface between the two materials.
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Quasi-2D Nanostripes On Silver Nanostructure Arrays
The team studied quasi-2D Ruddlesden-Popper perovskite nanostripes with the composition (C12H27N)2(MA)n-1(Pb)n(Br)3n+1. Prepared via a colloidal hot-injection method, the nanostripes are 1 to 7 µm long and 12 to 250 nm wide.
To build the devices, the researchers used colloidal lithography to form hexagonally ordered silver nanostructure arrays (ANA) between perforated Ag electrodes.
A self-assembled monolayer of octadecanethiol (ODT) was then applied to the ANA, and the perovskite nanostripes were deposited on top to complete the hybrid photodetector.
X-ray diffraction confirmed mixed-n Ruddlesden–Popper phases with reflections similar to bulk MAPbBr3. Optical measurements showed strong photoluminescence around 524 nm, while finite element simulations and reflectance spectra identified an LSPR mode in the ANA near 525 nm.
This close spectral overlap between LSPR and excitonic features is key to boosting photocurrent.
Time-resolved photoluminescence (TRPL) revealed an average lifetime of 9.6 ns for nanostripes in solution (excited at 375 nm), and was also used at 442 nm to probe exciton-plasmon coupling in nanostripes deposited on different substrates.
Strong Versus Weak Coupling
When perovskite nanostripes were placed directly on bare ANA, the system entered a strong coupling regime, with clear Rabi splitting in the spectra. Despite this apparently favourable coupling, device performance actually worsened: photocurrent under illumination decreased.
The authors link this to interfacial reactions between silver and the perovskite, such as the formation of AgBr driven by halide migration, as well as LSPR-induced local heating. Both effects promote non-radiative recombination, degrading the active material.
Introducing an ODT self-assembled monolayer between ANA and nanostripes changed the picture.
The thin organic layer increased the separation and chemically passivated the interface, shifting the system into a weak-to-intermediate coupling regime. Rabi splitting disappeared, but exciton–plasmon interactions remained strong enough to support efficient resonant energy transfer.
In this configuration, the enhanced photocurrent is attributed mainly to resonant energy transfer and PIRET, rather than to hot-electron injection or simple near-field field enhancement.
Performance Gains
The impact on device performance is substantial. Photodetectors based on perovskite nanostripes on ODT-functionalized ANA show a maximum photocurrent enhancement of 838 % compared with reference devices without ANA.
At low illumination power, the hybrid devices reach a photoresponsivity of 70.41 mA W-1, roughly an order of magnitude higher than the reference. The specific detectivity rises to 1.48 × 1011 Jones, while the external quantum efficiency reaches 21.55 %.
The devices are also faster. The rise time improves from about 1.29 to 0.35 seconds, and the fall time from 1.95 to 0.44 seconds. The 3 dB bandwidth more than doubles, from around 0.7 Hz for the reference device to 1.5 Hz for the ODT/ANA hybrid.
The authors note that the enhancement decreases at higher illumination powers, as LSPR-induced heating increases non-radiative recombination and accelerates local degradation.
This underlines the need to balance plasmonic enhancement with thermal management and interfacial stability.
A Framework For Hybrid Photodetectors
Overall, the study shows that tuning plasmon-exciton coupling via a simple organic monolayer can dramatically improve both sensitivity and speed in quasi-2D perovskite photodetectors, while avoiding the damage associated with direct metal contact.
The study also provides a practical design for plasmonic-perovskite hybrid devices fabricated with scalable, low-cost methods such as colloidal lithography.
Journal Reference
Malani S. B. et al. (2025). Boosting Photodetection via Plasmonic Coupling in Quasi-2D Mixed-n Ruddlesden-Popper Perovskite Nanostripes. Small e09443. DOI: 10.1002/smll.202509443