Oriented Growth of In-Oxo Chain Based Metal-Porphyrin Framework Thin Film for High-Sensitive Photodetector

Abstract

The potential of metal-organic frameworks (MOFs) for applications in optoelectronics results from a unique combination of interesting photophysical properties and straightforward tunability of organic and inorganic units. Here, it is demonstrated that using MOF approach chromophores can be assembled into well-ordered 1D arrays using metal-oxo strands as lead structure, and the resulting porphyrinic rows exhibit unique photophysical properties and allow the realization of highly sensitive photodetectors. A porphyrinic MOF thin film, In-TCPP surface-coordinated MOF thin films with [021] orientation is fabricated using a layer-by-layer method, from In(NO₃)₃ and TCPP (5,10,15,20-(4-carboxyphenyl)porphyrin). Detailed experimental and theoretical analysis reveals that the assembly yields a structure where In-oxo strands running parallel to the substrate fix the chromophoric linkers to yield 1D arrays of porphyrins. The frontier orbitals of this highly anisotropic arrangement are localized in these columnar arrangements of porphyrins and result in high photoactivity, which is exploited to fabricate a photodetector with record (as compared to other organic materials) responsivity in visible regime of 7.28 × 10¹⁴ Jones and short rise/fall times (0.07/0.04 s). This oriented MOF thin film-based high-sensitive photodetector provides a new avenue to use inorganic, stable lead structures to assemble organic semiconductors into regular arrays, thus creating a huge potential for the fabrication of optoelectronic devices.

Keywords: In‐oxo chains; metal‐porphyrin; metal–organic frameworks; oriented growth; photodetectors.

Scheme 1

Schematic illustration of In‐TCPP SURMOF grown on functionalized substrate by using layer‐by‐layer dipping method.

Figure 1

Characterization of In‐TCPP SURMOF: a) out‐of‐plane and in‐plane XRD pattern of In‐TCPP SURMOF and simulated XRD pattern of bulk In‐TCPP; b) the frequency decrease (−Δf) in the lbl growth process monitored by a QCM‐D (inset: sense chip assembled with In‐TCPP SURMOF); c) UV–vis spectra (inset: Tauc plot); d) N 1s region of XPS data.

Figure 2

a) Surface SEM image, b) cross‐sectional SEM image, and c) AFM image with roughness statistics of In‐TCPP SURMOF with 15 cycles; d) the thickness of In‐TCPP SURMOF with 5, 10, 15, and 20 LPE cycles.

Figure 3

a) Schematic diagram of In‐TCPP SURMOF‐based photodetector; b) responsivities versus light absorption of In‐TCPP SURMOF at different wavelengths pulses irradiation; c) the on/off ratio of mix‐oriented In‐TCPP thin film and In‐TCPP SURMOF with different thickness; d) time‐resolved photocurrent as a function of illumination wavelength at 10 V bias voltage; e) light intensity dependent I–V curves of In‐TCPP SURMOF; and f) the rise/fall times curve for In‐TCPP SURMOF illuminated with 420 nm light at 10 V bias voltage.

Figure 4

Band structure of a) In‐TCPP MOF and b) In‐oxo‐based chain model, and c) representation of the primitive Brillouin zone with the calculated path Γ→S→R→Z→Γ→Σ₀→Γ. Calculations with Crystal17 at the PBE‐D3(BJ)/POB‐TZVP level of theory. Structural models used in the calculations are represented in Figures S15–S16 (Supporting Information).