Ling Qidan

Bio: Ling Qidan is an academic researcher from Fujian Normal University. The author has contributed to research in topics: Polymer solar cell & Maleimide. The author has an hindex of 7, co-authored 17 publications receiving 1434 citations.

Fused Nonacyclic Electron Acceptors for Efficient Polymer Solar Cells.

Abstract: We design and synthesize four fused-ring electron acceptors based on 6,6,12,12-tetrakis(4-hexylphenyl)-indacenobis(dithieno[3,2-b;2′,3′-d]thiophene) as the electron-rich unit and 1,1-dicyanomethylene-3-indanones with 0–2 fluorine substituents as the electron-deficient units. These four molecules exhibit broad (550–850 nm) and strong absorption with high extinction coefficients of (2.1–2.5) × 105 M–1 cm–1. Fluorine substitution downshifts the LUMO energy level, red-shifts the absorption spectrum, and enhances electron mobility. The polymer solar cells based on the fluorinated electron acceptors exhibit power conversion efficiencies as high as 11.5%, much higher than that of their nonfluorinated counterpart (7.7%). We investigate the effects of the fluorine atom number and position on electronic properties, charge transport, film morphology, and photovoltaic properties.

Single-Junction Binary-Blend Nonfullerene Polymer Solar Cells with 12.1% Efficiency.

Abstract: A new fluorinated nonfullerene acceptor, ITIC-Th1, has been designed and synthesized by introducing fluorine (F) atoms onto the end-capping group 1,1-dicyanomethylene-3-indanone (IC). On the one hand, incorporation of F would improve intramolecular interaction, enhance the push-pull effect between the donor unit indacenodithieno[3,2-b]thiophene and the acceptor unit IC due to electron-withdrawing effect of F, and finally adjust energy levels and reduce bandgap, which is beneficial to light harvesting and enhancing short-circuit current density (JSC ). On the other hand, incorporation of F would improve intermolecular interactions through CF···S, CF···H, and CF···π noncovalent interactions and enhance electron mobility, which is beneficial to enhancing JSC and fill factor. Indeed, the results show that fluorinated ITIC-Th1 exhibits redshifted absorption, smaller optical bandgap, and higher electron mobility than the nonfluorinated ITIC-Th. Furthermore, nonfullerene organic solar cells (OSCs) based on fluorinated ITIC-Th1 electron acceptor and a wide-bandgap polymer donor FTAZ based on benzodithiophene and benzotriazole exhibit power conversion efficiency (PCE) as high as 12.1%, significantly higher than that of nonfluorinated ITIC-Th (8.88%). The PCE of 12.1% is the highest in fullerene and nonfullerene-based single-junction binary-blend OSCs. Moreover, the OSCs based on FTAZ:ITIC-Th1 show much better efficiency and better stability than the control devices based on FTAZ:PC71 BM (PCE = 5.22%).

Polymorphism-dependent fluorescence of bisthienylmaleimide with different responses to mechanical crushing and grinding pressure

Abstract: A herringbone structured compound, 3,4-bisthienylmaleimide (BTM), with reversible four-color and on/off switching upon external stimuli is reported here. Three kinds of BTM crystals with strong red (RC), orange (OC) and yellow (YC) fluorescence, as well as a brown solid (BS) with weak orange luminescence are obtained in the experiments. Heating, solvent vapor and pressure, including crushing and grinding, can reversibly switch BTM's emission between RC, OC, YC and BS. Base vapor (NEt3)-heating cycle treatment of BTM film in polystyrene can induce emission switching between bright/dark (on/off) states. The results of crystal structural analysis and photophysical property studies demonstrate that although OC and YC have the same crystal structure, they exhibit different fluorescent properties, due to their different surface structures. Heat induces metastable RC, with orderly π-stacking, to turn into stable OC or YC, with brick stone stacking. Crushing can damage the surface structure of OC and transform it into YC without altering the crystal structure. Grinding OC or YC destroys the orderly stacking to yield amorphous BS.

Molecular Optimization Enables over 13% Efficiency in Organic Solar Cells

Abstract: A new polymer donor (PBDB-T-SF) and a new small molecule acceptor (IT-4F) for fullerene-free organic solar cells (OSCs) were designed and synthesized The influences of fluorination on the absorption spectra, molecular energy levels, and charge mobilities of the donor and acceptor were systematically studied The PBDB-T-SF:IT-4F-based OSC device showed a record high efficiency of 131%, and an efficiency of over 12% can be obtained with a thickness of 100–200 nm, suggesting the promise of fullerene-free OSCs in practical applications

Non-fullerene acceptors for organic solar cells

Abstract: Non-fullerene acceptors (NFAs) are currently a major focus of research in the development of bulk-heterojunction organic solar cells (OSCs). In contrast to the widely used fullerene acceptors (FAs), the optical properties and electronic energy levels of NFAs can be readily tuned. NFA-based OSCs can also achieve greater thermal stability and photochemical stability, as well as longer device lifetimes, than their FA-based counterparts. Historically, the performance of NFA OSCs has lagged behind that of fullerene devices. However, recent developments have led to a rapid increase in power conversion efficiencies for NFA OSCs, with values now exceeding 13%, demonstrating the viability of using NFAs to replace FAs in next-generation high-performance OSCs. This Review discusses the important work that has led to this remarkable progress, focusing on the two most promising NFA classes to date: rylene diimide-based materials and materials based on fused aromatic cores with strong electron-accepting end groups. The key structure–property relationships, donor–acceptor matching criteria and aspects of device physics are discussed. Finally, we consider the remaining challenges and promising future directions for the NFA OSCs field. Non-fullerene acceptors have been widely used in organic solar cells over the past 3 years. This Review focuses on the two most promising classes of non-fullerene acceptors — rylene diimide-based materials and fused-ring electron acceptors — and discusses structure–property relationships, donor– acceptor matching criteria and device physics, as well as future research directions for the field.

Nonfullerene Acceptor Molecules for Bulk Heterojunction Organic Solar Cells

Abstract: The bulk-heterojunction blend of an electron donor and an electron acceptor material is the key component in a solution-processed organic photovoltaic device. In the past decades, a p-type conjugated polymer and an n-type fullerene derivative have been the most commonly used electron donor and electron acceptor, respectively. While most advances of the device performance come from the design of new polymer donors, fullerene derivatives have almost been exclusively used as electron acceptors in organic photovoltaics. Recently, nonfullerene acceptor materials, particularly small molecules and oligomers, have emerged as a promising alternative to replace fullerene derivatives. Compared to fullerenes, these new acceptors are generally synthesized from diversified, low-cost routes based on building block materials with extraordinary chemical, thermal, and photostability. The facile functionalization of these molecules affords excellent tunability to their optoelectronic and electrochemical properties. Within t...

Over 14% Efficiency in Polymer Solar Cells Enabled by a Chlorinated Polymer Donor.

Abstract: Fluorine-contained polymers, which have been widely used in highly efficient polymer solar cells (PSCs), are rather costly due to their complicated synthesis and low yields in the preparation of components. Here, the feasibility of replacing the critical fluorine substituents in high-performance photovoltaic polymer donors with chlorine is demonstrated, and two polymeric donors, PBDB-T-2F and PBDB-T-2Cl, are synthesized and compared in parallel. The synthesis of PBDB-T-2Cl is much simpler than that of PBDB-T-2F. The two polymers have very similar optoelectronic and morphological properties, except the chlorinated polymer possess lower molecular energy levels than the fluorinated one. As a result, the PBDB-T-2Cl-based PSCs exhibit higher open circuit voltage (Voc ) than the PBDB-T-2F-based devices, leading to an outstanding power conversion efficiency of over 14%. This work establishes a more economical design paradigm of replacing fluorine with chlorine for preparing highly efficient polymer donors.

Material insights and challenges for non-fullerene organic solar cells based on small molecular acceptors

Abstract: The field of non-fullerene organic solar cells has experienced rapid development during the past few years, mainly driven by the development of novel non-fullerene acceptors and matching donor semiconductors. However, organic solar cell material development has progressed via a trial-and-error approach with limited understanding of the materials’ structure–property relationships and the underlying device physics of non-fullerene devices. In addition, the availability of hundreds of donor and acceptor semiconductors creates an extremely large pool of possible donor–acceptor combinations, which poses a daunting challenge for rational material screening and matching. This Review describes several important conceptual aspects of the emerging non-fullerene devices by highlighting key contributions that provided fundamental insights regarding rational material design, donor–acceptor pair matching, blend morphology control and the reduced voltage losses in non-fullerene organic solar cells. We also discuss the key challenges that need to be addressed to develop more-efficient non-fullerene organic solar cells.