Potential of Nonfullerene Small Molecules with High Photovoltaic Performance

Abstract

Over the past decades, fullerene derivatives have become the most successful electron acceptors in organic solar cells (OSCs) and have achieved great progress, with power conversion efficiencies (PCEs) of over 11 %. However, fullerenes have some drawbacks, such as weak absorption, limited energy-level tunability, and morphological instability. In addition, fullerene-based OSCs usually suffer from large energy losses of over 0.7 eV, which limits further improvements in the PCE. Recently, nonfullerene small molecules have emerged as promising electron acceptors in OSCs. Their highly tunable absorption spectra and molecular energy levels have enabled fine optimization of the resulting devices, and the highest PCE has surpassed 12 %. Furthermore, several studies have shown that OSCs based on small-molecule acceptors (SMA) have very efficient charge generation and transport efficiency at relatively low energy losses of below 0.6 eV, which suggests great potential for the further improvement of OSCs. In this focus review, we analyze the challenges and potential of SMA-based OSCs and discuss molecular design strategies for highly efficient SMAs.

Low-Dimensional Hybrid Cuprous Halides Directed by Transition Metal Complex: Syntheses, Crystal Structures, and Photocatalytic Properties

“…[53][54] To data, numerous [Cu x X y ] (y-x)-anionic clusters or 6-, etc, have also been reported and characterized. [67][68][69][70][71][72][73][74][75][76][77][78][79][80] Relatively, three-dimensional (3D) frameworks are rarely documented with limited topological networks.…”

“…However, most of the SBUs are self-condensed to form etc [67][68][69][70][71][72][73][74][76][77][78][79][80] Occasionally, these SBUs can also be interlinked to form 2D microporous layers, for example, two isomeric 2D [Cu11 I 17 ] 6-layers are composed of [Cu 3 I 7 ], [Cu 4 I 8 ], [Cu 6 I 12 ] and [Cu 12 I 22 ] units in [deDABCO] 2 [meDABCO]Cu 11 I 17 .…”

Organic Photovoltaics over Three Decades

“…The recent avalanche of highly efficient devices based on donor/ acceptor blends with nonfullerene acceptors [14,233] has forced a re-evaluation of the strategies used for rational materials design. A number of reports verify that the LUMO-LUMO gap can be reduced close to zero, while still allowing considerable photocurrent to be generated.…”

Medium‐Bandgap Conjugated Polymer Donors for Organic Photovoltaics

“…Besides, the fullerene derivatives’ energy levels are difficult to tune because their chemical structures are hard to modify, which leads to high cost of fullerene derivatives with high purity. Therefore, fullerene derivatives are not deemed to be ideal electron acceptors . Recently, an increasing number of researchers have began to focus on developing the nonfullerene acceptor materials because of the unique merits of wide and efficient absorption in the visible and near‐infrared region, tunable energy levels, and low‐cost production .…”