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.
A chlorinated polymer donor, PBDB‐T‐2Cl, is synthesized and compared in parallel with its fluorinated counterpart, PBDB‐T‐2F. PBDB‐T‐2Cl exhibits a much simpler synthesis route, which is favorable for future practical application of organic solar cells; in addition, a high power conversion efficiency of 14.4% (with certified PCE of 13.9% by the National Institute of Metrology) and good stability tested over 1000 h is achieved.
The synergistic effect of fluorination on molecular energy level modulation is realized by introducing fluorine atoms onto both the donor and the acceptor moieties in a D–A polymer, and as a result, ...the polymer solar cell device based on the trifluorinated polymer, PBT‐3F, shows a high efficiency of 8.6%, under illumination of AM 1.5G, 100 mW cm−2.
Conspectus As researchers continue to develop new organic materials for solar cells, benzo1,2-b:4,5-b'dithiophene (BDT)-based polymers have come to the fore. To improve the photovoltaic properties ...of BDT-based polymers, researchers have developed and applied various strategies leading to the successful molecular design of highly efficient photovoltaic polymers. Novel polymer materials composed of two-dimensional conjugated BDT (2D-conjugated BDT) have boosted the power conversion efficiency of polymer solar cells (PSCs) to levels that exceed 9%. In this Account, we summarize recent progress related to the design and synthesis of 2D-conjugated BDT-based polymers and discuss their applications in highly efficient photovoltaic devices. We introduce the basic considerations for the construction of 2D-conjugated BDT-based polymers and systematic molecular design guidelines. For example, simply modifying an alkoxyl-substituted BDT to form an alkylthienyl-substituted BDT can improve the polymer hole mobilities substantially with little effect on their molecular energy level. Secondly, the addition of a variety of chemical moieties to the polymer can produce a 2D-conjugated BDT unit with more functions. For example, the introduction of a conjugated side chain with electron deficient groups (such as para-alkyl-phenyl, meta-alkoxyl-phenyl, and 2-alkyl-3-fluoro-thienyl) allowed us to modulate the molecular energy levels of 2D-conjugated BDT-based polymers. Through the rational design of BDT analogues such as dithienobenzodithiophene (DTBDT) or the insertion of larger π bridges, we can tune the backbone conformations of these polymers and modulate their photovoltaic properties. We also discuss the influence of 2D-conjugated BDT on polymer morphology and the blends of these polymers with phenyl-C61 (or C71)-butyric acid methyl ester (PCBM). Finally, we summarize the various applications of the 2D-conjugated BDT-based polymers in highly efficient PSC devices. Overall, this Account correlates the molecular structures of the 2D-conjugated BDT-based polymers with their photovoltaic properties. As a result, this Account can guide the molecular design of organic photovoltaic materials and the development of organic materials for other types of optoelectronic devices.
Advances in the design and application of highly efficient conjugated polymers and small molecules over the past years have enabled the rapid progress in the development of organic photovoltaic (OPV) ...technology as a promising alternative to conventional solar cells. Among the numerous OPV materials, benzodithiophene (BDT)-based polymers and small molecules have come to the fore in achieving outstanding power conversion efficiency (PCE) and breaking 10% efficiency barrier in the single junction OPV devices. Remarkably, the OPV device featured by BDT-based polymer has recently demonstrated an impressive PCE of 11.21%, indicating the great potential of this class of materials in commercial photovoltaic applications. In this review, we offered an overview of the organic photovoltaic materials based on BDT from the aspects of backbones, functional groups, alkyl chains, and device performance, trying to provide a guideline about the structure-performance relationship. We believe more exciting BDT-based photovoltaic materials and devices will be developed in the near future.
Ternary polymer solar cells are fabricated based on one donor PBDB‐T and two acceptors (a methyl‐modified small‐molecular acceptor (IT‐M) and a bis‐adduct of Bis70PCBM). A high power conversion ...efficiency of 12.2% can be achieved. The photovoltaic performance of the ternary polymer solar cells is not sensitive to the composition of the blend.
To make organic solar cells (OSCs) more competitive in the diverse photovoltaic cell technologies, it is very important to demonstrate that OSCs can achieve very good efficiencies and that their cost ...can be reduced. Here, a pair of nonfullerene small‐molecule acceptors, IT‐2Cl and IT‐4Cl, is designed and synthesized by introducing easy‐synthesis chlorine substituents onto the indacenodithieno3,2‐bthiophene units. The unique feature of the large dipole moment of the CCl bond enhances the intermolecular charge‐transfer effect between the donor–acceptor structures, and thus expands the absorption and down shifts the molecular energy levels. Meanwhile, the introduction of CCl also causes more pronounced molecular stacking, which also helps to expand the absorption spectrum. Both of the designed OSCs devices based on two acceptors can deliver a power conversion efficiency (PCE) greater than 13% when blended with a polymer donor with a low‐lying highest occupied molecular orbital level. In addition, since IT‐2Cl and IT‐4Cl have very good compatibility, a ternary OSC device integrating these two acceptors is also fabricated and obtains a PCE greater than 14%. Chlorination demonstrates effective ability in enhancing the device performance and facile synthesis route, which both deserve further exploitation in the modification of photovoltaic materials.
A pair of nonfullerene small‐molecule acceptors, IT‐2Cl and IT‐4Cl, is designed and synthesized by easy‐synthesis chlorine substituents. The CCl bond enhances the intermolecular charge‐transfer effect between the donor–acceptor structures and molecular structure order. Both binary devices show efficiency beyond 13%, and a ternary organic solar cell device integrating these two acceptors obtains an efficiency greater than 14%.
Abstract
Non-fullerene acceptors (NFAs) based on non-fused conjugated structures have more potential to realize low-cost organic photovoltaic (OPV) cells. However, their power conversion efficiencies ...(PCEs) are much lower than those of the fused-ring NFAs. Herein, a new bithiophene-based non-fused core (TT-P
i
) featuring good planarity as well as large steric hindrance was designed, based on which a completely non-fused NFA, A4T-16, was developed. The single-crystal result of A4T-16 reveals that a three-dimensional interpenetrating network can be formed due to the compact π–π stacking between the adjacent end-capping groups. A high PCE of 15.2% is achieved based on PBDB-TF:A4T-16, which is the highest value for the cells based on the non-fused NFAs. Notably, the device retains ~84% of its initial PCE after 1300 h under the simulated AM 1.5 G illumination (100 mW cm
−2
). Overall, this work provides insight into molecule design of the non-fused NFAs from the aspect of molecular geometry control.
Broadening the optical absorption of organic photovoltaic (OPV) materials by enhancing the intramolecular push-pull effect is a general and effective method to improve the power conversion ...efficiencies of OPV cells. However, in terms of the electron acceptors, the most common molecular design strategy of halogenation usually results in down-shifted molecular energy levels, thereby leading to decreased open-circuit voltages in the devices. Herein, we report a chlorinated non-fullerene acceptor, which exhibits an extended optical absorption and meanwhile displays a higher voltage than its fluorinated counterpart in the devices. This unexpected phenomenon can be ascribed to the reduced non-radiative energy loss (0.206 eV). Due to the simultaneously improved short-circuit current density and open-circuit voltage, a high efficiency of 16.5% is achieved. This study demonstrates that finely tuning the OPV materials to reduce the bandgap-voltage offset has great potential for boosting the efficiency.
Recently, the laboratory-scale power conversion efficiency (PCE) of organic solar cells (OSCs) has reached 18% in single-junction devices due to a combination of the rapid development of novel ...light-harvesting/interfacial materials and device engineering. Thus, such materials show considerable application prospects in the near future. It is of great importance to develop economically achievable, highly efficient, thickness-tolerant photovoltaic materials and processing methods for the manufacture of large flexible solar panels. Research in this area has been conducted from the very early stages of the development of organic photovoltaic materials and has never stopped. Herein, we focus on the fundamental requirements of photoactive materials and the processing methods used for commercialization based on the recent advances of the booming PCEs, to provide guidelines for future material design and mass production. In this review, the progress toward high-performance materials is briefly summarized, and the essential requirements for large-area printing modules, such as thickness tolerance and cost issues, and the latest findings on non-fullerene OSCs are introduced. In particular, important advances in the material design and device optimization of thick-film OSCs have been discussed. Significant advances in the processing methods used to prepare efficient non-fullerene OSCs and the challenges for the industrialization of OSCs are presented. Furthermore, the prospects and opportunities in this emerging field of research are also discussed.
The key factors for OSC materials toward application mainly include high performance, thickness tolerance, low cost, simple fabrication processing, high stability, and an environmentally-friendly nature.
To solve the problem of the design of the old people's recuperation space, the virtual information interaction platform is used to study the public art application in the design of the old people's ...recuperation space. Firstly, the principles of interactive design are expounded, and secondly, the existing institutions for the old people are investigated. Under the premise of optimizing the functions of the facilities, the concepts of humanistic care, emotional care and humanization in public art are integrated into the design of the old people's rehabilitation space, to solve the long-term negative impression of the old people's repression and indifference to the old people's care institutions. The construction of the scene allows the old people to experience some operations with the help of the virtual information interaction platform. In the modern elderly rehabilitation space, the attention and application of public art design will inevitably bring spiritual and material help to the old people in their later years, and create a happy, peaceful, and comfortable elderly life for them. The survey results manifest that 65.3% of urban old people and 71.8% of rural old people feel that they cannot keep up with the pace of development. Through the analysis and discussion of the physiological and psychological characteristics of the old people, the whole survey denotes that the physiological functions of the old people are declining, which seriously affects their normal life. Therefore, the design of the rehabilitation space for the old people should not only meet the basic needs of life, but also analyze the space design from the perspective of humanization and emotion. An ecological, natural, and human settlement environment has been established. The recuperation space is designed for the needs of different old people, which helps the old people to eliminate loneliness, enhance their value of the old people, and make life full of joy and meaning for the old people.
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