Morphology Control in Biphasic Hybrid Systems of Semiconducting Materials

Abstract

Simple blends of inorganic nanocrystals and organic (semiconducting) polymers usually lead to macroscopic segregation. Thus, such blends typically exhibit inferior properties than expected. To overcome the problem of segregation, polymer coated nanocrystals (nanocomposites) have been developed. Such nanocomposites are highly miscible within the polymer matrix. In this Review, a summary of synthetic approaches to achieve stable nanocomposites in a semiconducting polymer matrix is presented. Furthermore, a theoretical background as well as an overview concerning morphology control of inorganic NCs in polymer matrices are provided. In addition, the morphologic behavior of highly anisotropic nanoparticles (i.e. liquid crystalline phase formation of nanorod-composites) and branched nanoparticles (spatial orientation of tetrapods) is described. Finally, the morphology requirements for the application of inorganic/organic hybrid systems in light emitting diodes and solar cells are discussed, and potential solutions to achieve the required morphologies are provided.

From LC‐polymers to Nanomedicines: Different Aspects of Polymer Science from a Materials Viewpoint

“…A very large research topic evolved—during these years—out of work to functionalize (predominantly “shape anisotropic”) inorganic nanoparticles, to improve their solubility and processability in organic media . One aspect which makes these organic/inorganic hybrids interesting is the possibility to orient them—at high concentrations—into liquid crystalline phases, whereby the shape anisotropic inorganic core acts as “mesogen.” This made LC‐phases from many semiconducting nanoparticles and from carbon nanotubes available (see Figure and Figure S8, Supporting Information).…”

Functionalization of P3HT with Various Mono- and Multidentate Anchor Groups

“…This observation is in agreement with earlier reports on polymer-coated nanoparticles. 7,[9][10][11] TEM measurements ( Figure S17A, SI section) show individually dispersed nanoparticles in combination with rather small aggregates, whereby it is not clear if the aggregates are a result of the sample preparation process (dispersions were drop-coated onto a TEM grid and then dried) or whether the aggregates are stabilized by the presence of more than one anchor group on the polymer.…”

“…6 Consequently and from a chemical aspect, functional end groups facilitating an effective interaction of conjugated polymers with inorganic nanoparticles are desirable for hybrid optoelectronic devices. 7,8 This allows a homogeneous dispersion of inorganic and organic materials as well as an intimate molecular contact of both materials, which is beneficial for the preparation of photovoltaic devices from inorganic and organic materials and for the preparation of hybrid QD-LEDs (quantum dot light-emitting diodes). 7,[9][10][11] The advantageous effect of anchor groups on the performance of hybrid solar cells was first demonstrated by Liu et al 12 in 2004.…”

“…7,8 This allows a homogeneous dispersion of inorganic and organic materials as well as an intimate molecular contact of both materials, which is beneficial for the preparation of photovoltaic devices from inorganic and organic materials and for the preparation of hybrid QD-LEDs (quantum dot light-emitting diodes). 7,[9][10][11] The advantageous effect of anchor groups on the performance of hybrid solar cells was first demonstrated by Liu et al 12 in 2004. They studied hybrid solar cells composed of poly(3-hexylthiophene) (P3HT)/CdSe QDs and achieved an improved device performance upon the incorporation of an amino anchor group at the P3HT chain end.…”

“…Since the morphology of nanocomposite films depends on the stability of the polymer coating at the nanoparticle surface, the stability of the coating can be addressed by the number of binding sites and the affinity of the functional groups toward the respective inorganic surface. 7,19 Therefore, we incorporated both, mono-as well as multidentate anchor groups with varying functionalities (i.e., catechol, lipoic acid, amine and trithiocarbonate). 20 As the device performance strongly depends on the functional group interacting with the inorganic nanoparticles, the ability to incorporate different functional groups following the same polymer synthesis approach is of special interest for studies with the aim to investigate the influence of various functional groups on the device performance.…”