The printing of large‐area organic solar cells (OSCs) has become a frontier for organic electronics and is also regarded as a critical step in their industrial applications. With the rapid progress ...in the field of OSCs, the highest power conversion efficiency (PCE) for small‐area devices is approaching 15%, whereas the PCE for large‐area devices has also surpassed 10% in a single cell with an area of ≈1 cm2. Here, the progress of this fast developing area is reviewed, mainly focusing on: 1) material requirements (materials that are able to form efficient thick active layer films for large‐area printing); 2) modular designs (effective designs that can suppress electrical, geometric, optical, and additional losses, leading to a reduction in the PCE of the devices, as a consequence of substrate area expansion); and 3) printing methods (various scalable fabrication techniques that are employed for large‐area fabrication, including knife coating, slot‐die coating, screen printing, inkjet printing, gravure printing, flexographic printing, pad printing, and brush coating). By combining thick‐film material systems with efficient modular designs exhibiting low‐efficiency losses and employing the right printing methods, the fabrication of large‐area OSCs will be successfully realized in the near future.
The rapid development in large‐area organic solar cells (OSCs) is reviewed. Materials requirements, modular designs, and printing methods for large‐area OSCs are discussed. By combining thick‐film material systems with efficient modular designs, and then by employing the right printing methods, the fabrication of large‐area OSCs will be successfully realized in the near future.
Organic solar cells (OSCs) with nonfullerene acceptors (NFAs) exhibit efficient charge generation under small interfacial energy offsets, leading to over 18 % efficiency for the single‐junction ...devices based on the state‐of‐the‐art NFA of Y6. Herein, to reveal the underlying charge generation mechanisms, we have investigated the exciton binding energy (Eb) in Y6 by a joint theoretical and experimental study. The results show that owing to strong charge polarization effects, Y6 has remarkable small Eb of −0.11–0.15 eV, which is even lower than perovskites in many cases. Moreover, it is peculiar that the photoluminescence is enhanced with temperature, and the energy barrier for separating excitons into charges is evidently lower than the thermal energy according to the temperature dependence of photoluminescence, manifesting direct photogeneration of charge carriers enabled by weak Eb in Y6. Thus, charge generation in NFA‐based OSCs shows little dependence on interfacial driving forces.
Direct photogeneration of free charge carriers enabled by remarkably low exciton binding energies is demonstrated in the state‐of‐the‐art nonfullerene acceptor of Y6 by a joint experimental and theoretical study. This results in efficient charge generation under small interfacial energy offsets in the high‐efficiency nonfullerene organic solar cells.
Fine count two‐ply yarn supercapacitors are constructed from carbon nanotube yarns and polyaniline nanowires. The thread‐like supercapacitor possess excellent electrochemical capacity and are very ...strong and flexible. When being woven or knitted into wearable electronic devices, alone or in combination with conventional textile yarns, the two‐ply yarn supercapacitors can be flexed and stretched repeatedly without significant loss of capacitance.
The variation of the vertical component distribution can significantly influence the photovoltaic performance of organic solar cells (OSCs), mainly due to its impact on exciton dissociation and ...charge‐carrier transport and recombination. Herein, binary devices are fabricated via sequential deposition (SD) of D18 and L8‐BO materials in a two‐step process. Upon independently regulating the spin‐coating speeds of each layer deposition, the optimal SD device shows a record power conversion efficiency (PCE) of 19.05% for binary single‐junction OSCs, much higher than that of the corresponding blend casting (BC) device (18.14%). Impressively, this strategy presents excellent universality in boosting the photovoltaic performance of SD devices, exemplified by several nonfullerene acceptor systems. The mechanism studies reveal that the SD device with preferred vertical components distribution possesses high crystallinity, efficient exciton splitting, low energy loss, and balanced charge transport, resulting in all‐around enhancement of photovoltaic performances. This work provides a valuable approach for high‐efficiency OSCs, shedding light on understanding the relationship between photovoltaic performance and vertical component distribution.
High‐performance binary photovoltaic devices based on D18 and L8‐BO are constructed via manipulating the vertical component distribution in a sequential deposition (SD) process. After tuning the spin‐coating speeds of film deposition, the optimal SD device affords a record power conversion efficiency of 19.05% (certified, 18.9%) for binary single‐junction organic solar cells, much higher than that of the corresponding blend casting device (18.14%).
Polymer/small molecule/fullerene based ternary solar cells have made great progress and have attracted considerable attention in recent years. The addition of small molecules can effectively ...compensate for the disadvantages of polymer solar cells, such as increasing the light‐harvesting ability, providing cascade energy levels, and tuning the morphology. Thus, polymer/small molecule/fullerene based ternary solar cells are promising candidates to obtain further improvements in photovoltaic performance for organic solar cells. This article summarizes the developments of ternary solar cells with small molecules as third components, and represents the possible photo‐physics process in the ternary blends. In addition, the challenges and perspectives for ternary solar cells are discussed.
Ternary solar cells have made great progress in recent years. The state of polymer/small molecule/PCBM (fullerene acceptor) ternary systems is reviewed, with a focus on 1) the functions of small molecules, such as improving the light‐harvesting ability, 2) the photo‐physics process occurring in ternary systems, and 3) the influence of the small molecule on the crystallinity of the host polymer and the morphology of the active layer.
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.
Different scales of chirality endow a material with many excellent properties and potential applications. In this review, using π‐conjugated molecules as functional building blocks, recent progress ...on supramolecular helices inspired by biological helicity is summarized. First, induced chirality on conjugated polymers and small molecules is introduced. Molecular chirality can be amplified to nanostructures, superstructures, and even macroscopic structures by a self‐assembly process. Then, the principles for tuning the helicity of supramolecular chirality, as well as formation of helical heterojunctions, are summarized. Finally, the potential applications of chiral structures in chiral sensing and organic electronic devices are critically reviewed. Due to recent progress in chiral structures, an interdisciplinary area called “chiral electronics” is expected to gain wide popularity in the near future.
Conjugated molecules can be induced into a predominately single‐handed conformation by chiral dopants. The chiral molecules are then self‐assembled into helical nanostructures, superstructures, and even macroscopic structures. In this review paper, the principles that guide the formation, adjustment, and hierarchy of supramolecular helicity are critically reviewed. The potential application of chiral structures and areas for further investigation are also highlighted.
The high efficiency all-small-molecule organic solar cells (OSCs) normally require optimized morphology in their bulk heterojunction active layers. Herein, a small-molecule donor is designed and ...synthesized, and single-crystal structural analyses reveal its explicit molecular planarity and compact intermolecular packing. A promising narrow bandgap small-molecule with absorption edge of more than 930 nm along with our home-designed small molecule is selected as electron acceptors. To the best of our knowledge, the binary all-small-molecule OSCs achieve the highest efficiency of 14.34% by optimizing their hierarchical morphologies, in which the donor or acceptor rich domains with size up to ca. 70 nm, and the donor crystals of tens of nanometers, together with the donor-acceptor blending, are proved coexisting in the hierarchical large domain. All-small-molecule photovoltaic system shows its promising for high performance OSCs, and our study is likely to lead to insights in relations between bulk heterojunction structure and photovoltaic performance.
Poly(3‐hexyl thiophene) (P3HT) can be easily synthesized, demonstrating the large potential to decrease the cost in large‐scale synthesis. Thus, the development of novel non‐fullerene acceptor to ...match well with P3HT is urgent and necessary. The first benzotriazole‐containing non‐fullerene acceptor is designed and synthesized, and high open‐circuit voltage (V
oc) of 1.02 V, fill factor (FF) of 0.70, and power conversion efficiency (PCE) of 5.24% are realized, which are remarkably higher than that of P3HT: 6,6‐phenyl‐C61‐butyric acid methyl ester (PC61BM) system (V
oc = 0.59 V, FF = 0.57, and PCE = 3.34%).
Solution-processable small molecules for organic solar cells have attracted intense attention for their advantages of definite molecular structures compared with their polymer counterparts. However, ...the device efficiencies based on small molecules are still lower than those of polymers, especially for inverted devices, the highest efficiency of which is <9%. Here we report three novel solution-processable small molecules, which contain π-bridges with gradient-decreased electron density and end acceptors substituted with various fluorine atoms (0F, 1F and 2F, respectively). Fluorination leads to an optimal active layer morphology, including an enhanced domain purity, the formation of hierarchical domain size and a directional vertical phase gradation. The optimal morphology balances charge separation and transfer, and facilitates charge collection. As a consequence, fluorinated molecules exhibit excellent inverted device performance, and an average power conversion efficiency of 11.08% is achieved for a two-fluorine atom substituted molecule.
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