Tuning of the Photovoltaic Parameters of Molecular Donors by Covalent Bridging

Abstract

The synthesis of donor‐acceptor molecules involving triarylamines and dicyanovinyl blocks is described. Optical and electrochemical results show that rigidification of the acceptor part of the molecule by a covalent bridge leads to a ca. 0.20 eV increase of the band gap due to a parallel increase of the lowest unoccupied molecular orbital level. A preliminary evaluation of these compounds as donor materials in organic solar cells shows that although this structural modification reduces the light‐harvesting properties of the donor molecule, it nevertheless induces an increase of the efficiency of the resulting solar cells due to a simultaneous improvement of the open‐circuit voltage and fill factor.

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

“…20 The limited conjugation length also makes charge transport in these materials primarily intermolecular with a negligible intramolecular component, which increases charge recombination in OSCs.…”

“…A promising approach is to incorporate star-shaped conjugated structures into D-p-A conjugated systems. 7,8,20 These star-shaped molecules, which enhance intramolecular p-p interactions and extend the conjugated surface of small molecules, can effectively be utilized in OSCs using the doctor-bladed process. 7,8 These results drive us to pay more attention to the high performance star-shaped small molecules for OSCs.…”

Star-shaped D–π–A oligothiophenes with a tris(2-methoxyphenyl)amine core and alkyldicyanovinyl groups: synthesis and physical and photovoltaic properties

“…Meanwhile, alkoxy substituents at the phenyl rings of TPA have been successfully used in the design of asymmetrical D-A molecules for organic and hybrid organic solar cells. 32,33 Alkoxy substituents at the TPA core can increase the solubility, change intra-and intermolecular interactions as well as energy levels of the molecules, and thus influence the solid-state properties of pristine oligomers and their blends. However, the first example of a D-A star-shaped molecule with alkoxy groups at TPA, namely with the tris(2-methoxyphenyl)amine (m-TPA) core, has been reported recently.…”

Effects of oligothiophene π-bridge length on physical and photovoltaic properties of star-shaped molecules for bulk heterojunction solar cells

“…21,22 Furthermore, the limited conjugation length makes charge transport in these materials primarily intermolecular with a negligible intramolecular component, which increases charge recombination in OSCs causing low photocurrent and low ll factor (FF). 9 Overcoming these obstacles requires to enhance intramolecular p-p stacking interactions and facilitate charge transport and collection in D-A small molecule OSCs, as well as to further increase the PCE.…”