Flexible high-performance graphene hybrid photodetectors functionalized with gold nanostars and perovskites

Abstract

Hybrid materials in optoelectronic devices can provide synergistic effects that complementarily enhance the properties of each component. Here, flexible high-performance graphene hybrid photodetectors (PDs) are developed by introducing gold nanostars (GNSs) and perovskites for strong light trapping with hot electron transfer and efficient light harvesting characteristics, respectively. While pristine graphene PDs do not exhibit discernible photodetection properties due to the very low photon absorption and ultrafast charge carrier recombination, graphene PDs functionalized with GNSs and a densely covered perovskite layer exhibit outstanding photoresponsive properties with a photoresponsivity (R) of 5.90 × 104 A W−1 and a specific detectivity of 1.31 × 1013 Jones, the highest values among those reported for perovskite-functionalized graphene PDs thus far. Moreover, we fabricated a flexible 10 × 10 PD array that shows well-resolved spatiotemporal mapping of light signals with excellent operational and mechanical stabilities at a bending radius down to 3 mm and in repeated bending tests for over 1000 cycles. Comprehensive analyses using finite-difference time-domain (FDTD) theoretical calculations, scanning near-field optical microscopy, and photoluminescence mapping reveal the effective light trapping effect of GNSs and the charge carrier transfer between the perovskite and graphene. This work provides a new design platform for flexible and high-performance photodetection systems.

Plasmonic and Graphene-Functionalized High-Performance Broadband Quasi-Two-Dimensional Perovskite Hybrid Photodetectors

“…Also, the device dark current was consistent with that previously reported for integrated-structure PDs. , Figure d show the photo-response rising time (photocurrent from 10 to 90% as a light switch) and decay time (photocurrent from 90 to 10% as a light switch) of the n = 2 G–Au–P-PDs, for which the rise and decay times were 0.33 and 0.27 s, respectively. The photo-response times of the device were shorter than those reported in previous studies. , However, compared with the n = 2 G–Au–P-PDs, the n = 1 G–Au–P-PDs had a lower dark current and faster photo-response time (Figure S13c,d). For the quasi-2D perovskite, the reduction of quantum well thickness, ion migration, and vacancy defect decrease can effectively confine the charge transport within the quantum plane, leading to a severe charge carrier recombination, resulting in both the dark current and photocurrent decrease. , Therefore, the quasi-2D P-PDs with small quantum well thickness showed great potential for ultra-fast photon detection.…”

“…As shown in Figure a, under light illumination, the perovskite absorbs photons and produces a large number of electron–hole pairs. The Au nanoarray contributes to photoinduced electron and hole generation, owing to the enhanced SLPR field. , Moreover, owing to the difference between the work function of the metal and perovskite for an electron transfer, a Schottky junction will be generated at the interface between the perovskite and Au nanoarrays, forming an interfacial electric field from the perovskite to the Au nanoarray layer. The electron barrier in the interface layer can reduce the charge recombination and loss and thus effectively promote the separation and transfer of electron hole pairs. , On the other hand, because the Fermi energy level between the graphene and perovskite is inconsistent, the separation and transfer of electron–hole pairs occurred.…”

“…This is the main mechanism of dramatic PL intensity quenching and PL lifetime decay in the hybrid-structure perovskite. ,,, Therefore, the G–Au–P structure showed more obvious PL quenching and lifetime decay. This unique hybrid structure suppresses light-induced electron–hole pair recombination to a certain extent, allowing electrons to be extracted effectively from the perovskite, which increases the photocurrent. , The performance of some PDs based on perovskite and graphene hybrid structures are compared in Table . By comparison, our method is competitive in enhancing the performance and broaden the range of photo-response.…”

“…However, owing to polycrystalline nature of perovskite films, the quasi-2D thin films inevitably have structural and grain boundary defects, resulting in poor charge transport ability and lower carrier mobility. , Furthermore, owing to the limited band gap of these perovskite-based PDs, when the wavelength of incident light is in the near-infrared (NIR) range, the photocurrent is very small and generally close to zero. , The structure and performance thus cannot fulfill the requirements of practical applications. More precisely, power conversion efficiency, processing speed of photoelectric signals, and further improvement in its performance have all encountered certain bottlenecks. , In order to overcome the problems above and realize high-performance broadband perovskite PDs, an appropriate interface material is needed. ,,, Effective strategies by combining perovskites with high-mobility 2D materials (such as graphene) and localized surface plasmon resonance (LSPR) metal nanostructures, to create heterojunctions, can improve carrier transport and photoresponsivity in the NIR region. ,,, For heterojunction PDs, effective charge transfer between the graphene and the perovskite can be achieved. , Perovskites absorb light and generate a large number of electron–hole pairs. The holes in the perovskite valence band can be transferred to the graphene layer, which leads to the loss of hole states in the perovskite and in turn reduces the recombination of photoexcited electron–hole pairs.…”

A Flexible Plasmonic-Membrane-Enhanced Broadband Tin-Based Perovskite Photodetector

“…Besides, the asymmetric plasmonic nanostructures can provide an extra polarization sensitivity to photodetectors based on low-dimensional materials, which further expand their applicability. , Moreover, PCs and DBRs are usually made of large-scale periodic nanostructures on rigid substrates, which is clearly not feasible for flexible devices, , while self-assembled plasmonic nanostructures can provide mechanical tension-offset and thus retain the original optical response under strain . Recently, a few studies have demonstrated plasmon-enhanced flexible, lead-based perovskite photodetectors yet with limited photocurrent enhancement, , which could be attributed to the fact that the perovskite films were directly deposited on the surface of noble metal nanostructures without introducing dielectric spacers between them. Although metallic nanostructures supporting localized surface plasmon resonance (LSPR) can significantly increase the light absorption of the active materials next to them, − typically within a few tens of nanometers around them, energy transfer and charge transfer from the perovskite materials to the metal nanostructures could also occur and cause dramatic loss of photogenerated electron–hole pairs.…”