Pierre Josse

Phthalimide end-capped thienoisoindigo and diketopyrrolopyrrole as non-fullerene molecular acceptors for organic solar cells

Two acetylene-bridged molecules, built by grafting phthalimides on thienoisoindigo (TII) and diketopyrrolopyrrole (DPP) blocks, have been synthesized, characterized and evaluated as electron acceptor materials in air-processed inverted organic solar cells. Once blended with poly(3-hexylthiophene), power conversion efficiencies (PCEs) of ca. 0.4% and 3.3% were achieved for TII and DPP based devices, respectively. To the best of our knowledge these PCEs (i) rank amongst the highest reported so far for diketopyrrolopyrrole based acceptors and (ii) make this contribution the very first example of thienoisoindigo based materials used as non-fullerene electron acceptors.

Applying direct heteroarylation synthesis to evaluate organic dyes as the core component in PDI-based molecular materials for fullerene-free organic solar cells

Direct heteroarylation has emerged as a versatile and powerful tool to access π-conjugated materials through atom-economical Pd-catalyzed carbon–carbon bond forming reactions. Employing this synthetic protocol has enabled the facile evaluation of a series of organic dyes in a PDI-dye-PDI framework. Material properties are largely dictated by the PDI components, but the incorporation of either thienoisoindigo, diketopyrrolopyrrole or isoindigo has been shown to influence the ionization potential and absorption profiles of the final materials. Solution-processable organic solar cell devices were fabricated to investigate the influence of the different dye cores on photovoltaic performance when paired with the donor polymer PTB7-Th. It was found that the diketopyrrolopyrrole-based material out-performed the other organic dyes, demonstrating energy losses of less than 0.6 eV, promising efficiencies when cast from non-halogenated solvents and the ability to dictate self-assembly induced by small volume fractions of the high-boiling solvent additive 1,8-diiodooctane to reach best device efficiencies of 4.1%.

Enantiopure versus Racemic Naphthalimide End-Capped Helicenic Non-fullerene Electron Acceptors: Impact on Organic Photovoltaics Performance

Impact of the enantiopurity on organic photovoltaics (OPV) performance was investigated through the synthesis of racemic and enantiomerically pure naphthalimide end-capped helicenes and their application as non-fullerene molecular electron acceptors in OPV devices. A very strong increase of the device performance was observed by simply switching from the racemic to the enantiopure forms of these π-helical non-fullerene acceptors with power conversion efficiencies jumping from 0.4 to about 2.0 % in air-processed poly(3-hexylthiophene)-based devices, thus highlighting the key role of enantiopurity in the photovoltaic properties.

Pentaerythritol based push–pull tetramers for organic photovoltaics

The synthesis and characterization of two tetramers based on the functionalization of a central pentaerythritol σ-linker with push–pull chromophores is reported herein. Prepared in only few steps, these original molecules exhibit interesting optical and electrochemical properties. Moreover, once evaluated as donor materials, promising power conversion efficiencies of 4.5% were reached when blended with the [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) in bulk heterojunction solar cells.

Bromination of the benzothioxanthene Bloc: toward new π-conjugated systems for organic electronic applications

A selective and efficient method to afford a monobrominated benzothioxanthene (Br-BTXI) derivative is reported. Br-BTXI was extensively employed in common palladium catalyzed coupling reactions. Finally, as a proof of concept, a BTXI based molecular donor was synthesized and evaluated in bulk heterojunction solar cells.

Direct (Hetero)Arylation Polymerization of a Spirobifluorene and a Dithienyl-Diketopyrrolopyrrole Derivative: New Donor Polymers for Organic Solar Cells

The synthesis and preliminary evaluation as donor material for organic photovoltaics of the poly(diketopyrrolopyrrole-spirobifluorene) (PDPPSBF) is reported herein. Prepared via homogeneous and heterogeneous direct (hetero)arylation polymerization (DHAP), through the use of different catalytic systems, conjugated polymers with comparable molecular weights were obtained. The polymers exhibited strong optical absorption out to 700 nm as thin-films and had appropriate electronic energy levels for use as a donor with PC70BM. Bulk heterojunction solar cells were fabricated giving power conversion efficiencies above 4%. These results reveal the potential of such polymers prepared in only three steps from affordable and commercially available starting materials.