Photoinduced Charge Separation in Molecular Silicon

Abstract

Interest in molecular silicon semiconductors arises from the properties shared with bulk silicon like earth abundance and the unique architectures accessible from a structure distinctly different than rigid π-conjugated organic semiconductors. We report ultrafast spectroscopic evidence for direct, photoinduced charge separation in molecular silicon semiconductors that supports the viability of molecular silicon as donor materials in optoelectronic devices. The materials in this study are σ-π hybrids, in which electron-deficient aromatic acceptors flank a σ-conjugated silicon chain. Transient absorption and femtosecond-stimulated Raman spectroscopy (FSRS) techniques revealed signatures consistent with direct, optical charge transfer from the silane chain to the acceptor; these signatures were only observed by probing excited-state structure. Our findings suggest new opportunities for controlling charge separation in molecular electronics.

2D Oligosilyl Metal–Organic Frameworks as Multi‐state Switchable Materials

“…Herein, we present two examples of MOFs capable of reversible structural transformations between multiple crystalline or amorphous phases. Oligosilanes, molecules with Si−Si bonds, are a class of hybrid inorganic‐organic materials with remarkable light absorption and charge transport properties that uniquely combine flexibility and strong light absorption, a property that inspired us to construct 2D MOFs based on oligosilyl linkers. While organosilicon species have been previously used in MOF formation, the organic linker usually contains a single Si atom, which precludes access to properties inherent to σ‐conjugated extended oligosilanes.…”

Synthesis of a Fragment of Crystalline Silicon: Poly(Cyclosilane)

“…[40] Poly(1) strongly absorbs ultraviolet light and the onset of absorbance is red-shifted 50 nm relative to monomer 1 (Figure 4), suggesting delocalization consistent with s-conjugation along the polysilane framework. [8] In conclusion, we report a synthetic approach to polycyclic silanes inspired by a one-dimensional fragment of the crystalline silicon lattice. We exploit poly(1)s s-conjugation in the synthesis of a novel donor-acceptor polymer.…”

“…The application of rational synthesis to organic materials chemistry leads to the isolation of innovative and well-defined materials inaccessible by top-down methods. [5,6] Current efforts focus on organic side chains: hybrid s,p-silanes are efficient hole transport materials [7] and undergo intramolecular photoinduced charge transfer, [8] donor-acceptor systems display nonlinear optical behavior, [9,10] and stereogenic centers or fluorinated groups control the global conformation and absorbance properties in helically chiral polysilanes. [4] Yet increased structural complexity in polysilanes has great potential to lead to novel properties.…”

“…[4] Yet increased structural complexity in polysilanes has great potential to lead to novel properties. [5,6] Current efforts focus on organic side chains: hybrid s,p-silanes are efficient hole transport materials [7] and undergo intramolecular photoinduced charge transfer, [8] donor-acceptor systems display nonlinear optical behavior, [9,10] and stereogenic centers or fluorinated groups control the global conformation and absorbance properties in helically chiral polysilanes. [11][12][13] Herein we describe a synthetic approach to increasing the complexity of the silicon framework itself.…”

2D Oligosilyl Metal–Organic Frameworks as Multi‐state Switchable Materials

“…Herein, we present two examples of MOFs capable of reversible structural transformations between multiple crystalline or amorphous phases.Oligosilanes,molecules with SiÀ Si bonds,a re ac lass of hybrid inorganic-organic materials with remarkable light absorption and charge transport properties [11][12][13][14][15][16] that uniquely combine flexibility and strong light absorption, ap roperty that inspired us to construct 2D MOFs based on oligosilyl linkers.While organosilicon species have been previously used in MOF formation, [17][18][19][20] the organic linker usually contains as ingle Si atom, which precludes access to properties inherent to s-conjugated extended oligosilanes.…”