Singlet Fission Materials for Photovoltaics: from Small Molecules to Macromolecules

Singlet fission (SF) is a spin-allowed process in which a singlet state splits into two triplet states. Materials that enable SF have attracted great attention in the last decade, mainly stemming from the potential of overcoming the Shockley-Queisser (SQ) limit in photoenergy conversion. In the past decade, a large number of new molecules exhibiting SF have been explored and many devices based on SF materials have been studied, though the mechanistic understanding is still obscure. This review focuses on the recent developments of SF materials, including small molecules, oligomers and polymers. The molecular design strategies and related mechanisms of SF are discussed. Then the dynamics of charge transfer and energy transfer between SF materials and other materials are introduced. Further, we discuss the progresses of implementing SF in photovoltaics. It is hoped that a comprehensive understanding to the SF materials, devices and mechanism may pave a new way for the design of next generation photovoltaics. This article is protected by copyright. All rights reserved.

Thiazole fused S,N-heteroacene step-ladder polymeric semiconductors for organic transistors

Ladder-type thiazole-fused S,N-heteroacenes with an extended π-conjugation consisting of six (SN6-Tz) and nine (SN9-Tz) fused aromatic rings have been synthesized and fully characterized.

An electron rich indaceno [2,1-b:6,5-b′] dithiophene derivative as a high intramolecular charge transfer material in dye sensitized solar cells

The synthesis, characterisation and photovoltaic performance of an indacenodithiophene (IDT)-based organic dye in DSSCs has been presented.

Functionalized Amphiphilic Diblock Fullerene Derivatives as a Cathode Buffer Layer for Efficient Inverted Organic Solar Cells

The amphipathic interface layer sandwiched between cathode and active layers had always played a role to balance interface compatibility and interfacial energy barriers in inverted organic solar cell (OSC) devices. Two functionalized amphiphilic diblock fullerene derivatives named C60-2DPE and C60-4HTPB were synthesized and applied as an interface layer in modifying zinc oxide (ZnO). Based on their amphipathic characteristics, the solvent treatment was introduced to cause an obvious self-assembly of the two materials on ZnO. The introduced cathode buffer layer could improve the interface compatibility between ZnO and the organic active layer effectively with its amphipathic blocks. Based on the PTB7-Th:PC71BM system, the OSC devices with a functionalized fullerene derivative layer could reach a power conversion efficiency of 9.21 and 8.86% for C60-2DPE and C60-4HTPB , respectively.

Effect of chalcogen atoms on the electronic band gaps of donor-acceptor-donor type semiconducting polymers: a systematic DFT investigation

We systematically investigated and compared the electronic band gaps of 16 different donor-acceptor-donor type semiconducting polymer systems that included different chalcogen atoms in their donor and acceptor units. The five-membered heterocyclic rings furan, thiophene, selenophene, and tellurophene were considered as electron donor units, whereas benzochalcogenadiazole groups, i.e., benzoxadiazole, benzothiadiazole, benzoselenadiazole, and benzotelluradiazole, were used as electron acceptor units. Our findings from B3LYP/6-31G(d) and B3LYP/LANL2DZ calculations performed with and without the polarizable continuum model indicated that the size of the chalcogen atom used as a heteroatom in the donor units plays a more important role than the size of the chalcogen atom in the benzochalcogenadiazole acceptor unit does. On the other hand, our results also suggest that the best way to modify and narrow the electronic band gap is to use heavy chalcogen atoms in both donor and acceptor units.

Synthesis of an indacenodithiophene-based fully conjugated ladder polymer and its optical and electronic properties

A fully conjugated ladder polymer (PFIDT) based on the indacenodithiophene unit was synthesized via a simple strategy.