Tuning the Optoelectronic Properties of Nonfullerene Electron Acceptors

Abstract

Broad spectral coverage over the solar spectrum is necessary for photovoltaic technologies and is a focus for organic solar cells. We report a series of small-molecule, nonfullerene electron acceptors containing the [(benzo[c][1,2,5]thiadiazol-4-yl)methylene]malononitrile unit as a high electron affinity component. The optoelectronic properties of these molecules were fine-tuned with the objective of attaining strong absorption at longer wavelengths by changing the low-ionization-potential moiety. The electron-accepting function of these materials was investigated with poly(3-n-hexylthiophene) (P3HT) as a standard electron donor. Significant photocurrent generation in the near infrared region, with an external quantum yield reaching as high as 22 % at 700 nm and an onset >800 nm was achieved. The results support efficient hole transfer to P3HT taking place after light absorption by the acceptor molecules. A Channel II-dominated power conversion efficiency of up to 1.5 % was, thus, achieved.

Molecular electron-acceptors based on benzodithiophene for organic photovoltaics

“…The devices present a short-circuit current density (J sc ) of 0.84 mA cm À2 and an open-circuit voltage (V oc ) of 1.02 V which combined with a low fill factor (FF) of 0.23 gave a power conversion efficiency (PCE) of 0.24%. Although modest this value is comparable to the results recently reported for BHJ cells based on other small size molecular acceptors tested with poly(3-hexylthiophene), 21 however it must be underlined that in our case both the donor and acceptor materials are small molecules. On the other hand, the high V oc , consistent with the deep LUMO level of compound 1 ranks among the highest reported so far for molecular BHJ cells.…”

Temperature‐Dependent Aggregation Donor Polymers Enable Highly Efficient Sequentially Processed Organic Photovoltaics Without the Need of Orthogonal Solvents

“…In recent years, due to the impressive development of nonfullerene acceptors (NFAs), power conversion efficiency (PCE) of over 14% has been achieved for single/multijunction bulk‐heterojunction (BHJ) architecture organic photovoltaics (OPVs) . In general, BHJ morphology is prepared using a one‐step method from the blend solution of donor and acceptor materials, which is denoted as the blend‐casting (BC) method herein.…”

Synthesis and Characterisation of Non-Fullerene Electron Acceptors for Organic Photovoltaics

“…The final class of NFA compounds that will be discussed is based on linear (calamitic) fused ring systems. Frequently these take the same approach as for low-bandgap D-A polymers is usually chosen to be a relatively electron-rich unit such as fluorene, [79][80][81] dibenzosilole, 82,83 indacenodithiophene, 84,85 or indacenodithieno [3,2-b]thiophene. 86 These structures all have positions that can be easily functionalised with solubilising alkyl groups, which allows the crystallinity and solubility of the material to be controlled without sterically crowding the other electron-poor sections of the molecule.…”