Solution‐Processed Bulk‐Heterojunction Solar Cells Based on Monodisperse Dendritic Oligothiophenes

Abstract

A novel family of soluble conjugated dendritic oligothiophenes (DOTs) as monodisperse 3D macromolecular architectures was characterized with respect to optical and redox properties in solution and in solid films. Band gaps of 2.5–2.2 eV, typical for organic semiconductors, were determined as well as HOMO/LUMO energy levels ideal for efficient electron transfer to acceptors such as [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) identifying them as suitable materials for solar cell applications. Solution‐processed bulk‐heterojunction solar cells using DOTs as electron donor and PCBM as acceptor were prepared and investigated. High open‐circuit voltages VOC of 1.0 V and power‐conversion efficiencies up to 1.72% were obtained for the DOT‐based devices. The higher generations DOTs provide the highest efficiencies. Based on the monodispersity of the DOTs, an analysis of the molar ratio between donor and acceptor in the blended film was possible leading to an optimal value of five to six thiophene units per PCBM.

A star-shaped D–π–A small molecule based on a tris(2-methoxyphenyl)amine core for highly efficient solution-processed organic solar cells

“…[4][5][6] The current research pursuits for small molecule-based OSCs target even higher efficiencies by designing and synthesizing new organic small molecules, such as star-or X-shaped molecules and [7][8][9][10] one-or two-dimensional oligomers with D-A-D or A-D-A structures. 3,[11][12][13][14][15][16] In particular, the most promising organic small molecule donor materials for photovoltaic applications are normally built by connecting various electron donating (donor) and electron capturing (acceptor) moieties through a p-conjugating spacer (D-p-A).…”

Conjugated Thiophene Dendrimer with an Electron-Withdrawing Core and Electron-Rich Dendrons: How the Molecular Structure Affects the Morphology and Performance of Dendrimer:Fullerene Photovoltaic Devices

“…10 π-Conjugated dendrimers are a particular class of molecules with a highly branched structure that offers the possibility to "fill space" with electronically active groups without obstruction from the solubilizing groups. 11 Previously we have reported on the synthesis, 12,13 spectroscopy, 14,15 charge transport, 16,17 and photovoltaic properties 18 of conjugated dendrimers composed of a phenyl core with conjugated thiophene dendrons ("arms") attached at ortho, para, and meta positions on the core. These dendrimers were primarily first generation, i.e., the dendron only had one branching point, with the number of R-linked thiophenes in the arm ranging from three to five, making these structures two-dimensional.…”

Solvent effects on the properties of hyperbranched polythiophenes

“…25 In the particular, all-Th dendrons and dendrimers, hereafter denoted nT (where n is the number of Th rings), behave as p-type semiconductors, being proposed as components of photovoltaic devices and organic solar cells. 24,26,27 Therefore, understanding of the electronic properties of nT is a key stage not only in the ongoing evolution of these systems for their promising applications but also in the development of new alternatives to conventional oligothiophenes and polythiophenes in the organic semiconductor field. The ionization potential (IP) and  g of nT (with n= 3, 9, 21 and 45 for dendrons and n= 6, 18, 42, 90 for dendrimers) were recently investigated in solution using cyclic voltammetry (CV) and UV-vis spectroscopy.…”