The influence of surface functionalization methods on the performance of silicon nanocrystal LEDs

Abstract

The influence of silicon nanocrystal (SiNC) surface characteristics obtained from different functionalization methods on the performance of LEDs was investigated. The surface of SiNCs was functionalized with hexyl chains via hydrosilylation (HS) or with organolithium reagents (OLR) and resulting SiNCs were incorporated as the emissive layer in hybrid organic/inorganic LEDs. Devices utilizing SiNCs functionalized with OLR consistently exhibited lower turn-on voltages, higher luminances and external quantum efficiencies compared to those obtained from the HS method. These improvements were attributed to the less dense and monolayer surface coverage of the SiNCs obtained by the OLR method, as well as their higher absolute quantum yield.

Broadband Forward Light Scattering by Architectural Design of Core–Shell Silicon Particles

“…Fourier transformed infrared (FTIR) spectroscopy (Figure 1L) reveals the presence of Si–H and Si–OH bonds in the particles, though their relative intensity varies with changing precursor ratio. The intensity of the SiO x bond stretching (at ≈1050 cm −1 ) [ 21,28 ] and of the O y –SiH x bond wagging (at ≈880 cm −1 ) [ 29 ] increases with respect to the SiH x bond stretching (≈2100 cm −1 ) [ 21,28 ] and bending (≈660 cm −1 ) [ 28 ] for increasing molar ratios of the silicon bisamadinate complex. This trend confirms that SiO x N y shell thickness increases with increasing molar ratio, as observed by scanning transmission electron microscopy coupled with energy dispersive X‐rays spectroscopy (STEM‐EDX).…”

Surface Engineering of Silicon Quantum Dots: Does the Ligand Length Impact the Optoelectronic Properties of Light‐Emitting Diodes?

“…[ 18,19 ] Especially SiQDs have gained significant attention in numerous research fields, such as solar cells, [ 20 ] nonlinear optics, [ 21 ] sensors, [ 22 ] biomedical applications, [ 23 ] field‐effect transistors, [ 24 ] and LEDs. [ 25 ] Suitable SiQDs for LED fabrication are commonly synthesized via bottom−up and top−down approaches, namely, plasma synthesis [ 26,27 ] and solid‐state etching from SiO x matrixes. [ 28,29 ] In LEDs, SiQDs are usually embedded in a hybrid multilayer OLED structure and act as the active emitting material.…”

“…[ 28,29 ] In LEDs, SiQDs are usually embedded in a hybrid multilayer OLED structure and act as the active emitting material. [ 25,30,31 ] High‐efficiency SiQD LEDs have been demonstrated with external quantum efficiencies (EQE) of up to 8.6%. [ 32 ] Furthermore, multicolor LEDs were fabricated, showing the diversity of SiQD‐based LED technology by changing the SiQD size.…”

“…It was found that the functionalization with organolithium reagents (OLR) leads to less overall surface coverage in contrast to HS, which results in a denser film packing and therefore a higher conductivity. [ 25,44 ] Functionalized by HS or OLR, many SiQD LEDs exhibit a blue shift of the electroluminescence (EL) spectra with increasing voltages. [ 25,29 ] Because the bandgap is inversely proportional to the SiQD size and ensembles of SiQDs always exhibit minor differences in size, higher‐bandgap QDs (i.e., smaller size) only become accessible as the voltage increases.…”

Si/SiO2 Core/Shell Luminescent Silicon Nanocrystals and Porous Silicon Powders With High Quantum Yield, Long Lifetime, and Good Stability

“…The confinement somewhat depends on the type of organic group attached to the surface [20]. Due to the long organic chains, these organically-capped SiNCs usually take a paste (slurry-like) form, not ideal for electroand opto-devices [39]. Moreover, they can easily agglomerate by phase separation when incorporated in a different matrix.…”