Recent Advances in Structural Design of Efficient Near‐Infrared Light‐Emitting Organic Small Molecules

Abstract

Organic light‐emitting materials in the near‐infrared (NIR) region are important to realize next‐generation lightweight and wearable applications in bioimaging, photodynamic therapy, and telecommunications. Inorganic and organometallic light‐emitting materials are expensive and toxic; thus, the development of purely organic light‐emitting materials is essential. However, the development of highly efficient NIR light‐emitting materials made of organic materials is still in its infancy. Therefore, this review outlines molecular design strategies for developing organic small‐molecule NIR light‐emitting materials with high emission efficiency that can overcome the energy‐gap law to be applied to next‐generation wearable devices. After briefly reviewing the basic knowledge required for the NIR emission of organic molecules, representative high‐efficiency molecules reported over the past 5 years are classified according to their core moieties, and their molecular design, physical properties, and luminescence characteristics are analyzed. Further, the perspective and outlook regarding the development of next‐generation high‐efficiency NIR organic light‐emitting materials are provided.

Orange/Red Benzo[1,2-b:4,5-b′]dithiophene 1,1,5,5-Tetraoxide-Based Emitters for Luminescent Solar Concentrators: Effect of Structures on Fluorescence Properties and Device Performances

“…Flash column chromatography was performed using Merck Kieselgel 60 (300−400 mesh) as the stationary phase. 1 H NMR spectra were recorded at 200, 300, or 400 MHz, and 13 C NMR spectra were recorded at 100.6 MHz, with Bruker Avance or Varian Mercury series instruments. Chemical shifts are referenced to the residual solvent peak (CHCl 3 , δ 7.26 ppm for 1 H NMR and δ 77.0 ppm for 13 C NMR; THF-d 8 , δ 1.72 and 3.58 ppm for 1 H NMR and δ 67.21 and 25.31 ppm for 13 C NMR).…”

“…1 H NMR spectra were recorded at 200, 300, or 400 MHz, and 13 C NMR spectra were recorded at 100.6 MHz, with Bruker Avance or Varian Mercury series instruments. Chemical shifts are referenced to the residual solvent peak (CHCl 3 , δ 7.26 ppm for 1 H NMR and δ 77.0 ppm for 13 C NMR; THF-d 8 , δ 1.72 and 3.58 ppm for 1 H NMR and δ 67.21 and 25.31 ppm for 13 C NMR). Coupling constants (J) are expressed in Hz, while the used abbreviations are s (singlet), d (doublet), dd (doublet of doublets), t (triplet), td (triplet of doublets), and m (multiplet).…”

“…Computational analysis; synthetic procedure for the preparation of compound 1; copies of the 1 H and 13 C NMR spectra of all new compounds; additional spectroscopic characterization of the compounds in solution and in the PMMA matrix; TAS analysis; experimental details on the optical and PV efficiency measurements; and experimental details on the accelerated lifetime tests (PDF)…”

“…J = 7.4 Hz, 6 H) ppm 13. C NMR (CDCl 3 , 100 MHz): δ 156.8, 143.3, 139.4, 133.5, 130.5, 129.0, 128.4, 127.5, 126.6, 125.4, 118.8, 117.5, 114.9, 78.9, 55.5, 40.4, 30.2, 29.7, 29.0, 23.7, 23.0, 14.1, 11.2 ppm.…”

Efficient Near-Infrared Luminescence of Self-Assembled Platinum(II) Complexes: From Fundamentals to Applications

“…First, eq represents the well-known energy gap law, showing that k IC accelerates exponentially as the energy gap Δ E decreases owing to the increased Franck–Condon overlaps. This is also the main reason for poor efficiencies in NIR emitters. − Second, both eqs and indicate that high vibrational frequencies and λ contribute to the rise of k IC . As a result, reducing vibrational frequencies associated with electronic transitions and λ is the core concept of the approaches to suppress nonradiative IC rates in the NIR spectral window.…”