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a) Chemical structures of SM1, SM1‐S, SM1‐F, and Y6. b) Conventional device structure used in SM‐OSCs. c) Absorption profiles of SM1, SM1‐S, SM1‐F, and Y6 in film state. d) Schematic energy diagram of the materials involved in the SM‐OSCs.
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It is very important to fine‐tune the nanoscale morphology of donor:acceptor blend active layers for improving the photovoltaic performance of all‐small‐molecule organic solar cells (SM‐OSCs). In this work, two new small molecule donor materials are synthesized with different substituents on their thiophene conjugated side chains, including SM1‐S w...
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... Moreover, thermal annealing has been commonly applied to improve organic solar cell performance through improved polymer crystallinity and phase separation. 23,24 To overcome the limitations of annealing temperature for OSCs on PHEMA, we introduce a small liquid-crystal molecule C8-BTBT, into the P3HT:PCBM system to improve anisotropic organic crystallization without thermal annealing. The C8-BTBT molecule consists of two thiophene rings and adjacent benzene rings connected with alkyl side chains, which enable its liquid crystal behavior as the rigid part (thiophene rings) favors both orientational and positional order while the rest of the molecule is flexible. ...
Solar energy is potentially the largest source of renewable energy for providing electrical power for human society. However, significant advances are required to make photovoltaic technologies have a low-carbon footprint in manufacture, be environmentally friendly at the end of their lives through recyclability, and be biodegradable. Here we report dissolvable organic photovoltaic devices based on poly(2-hydroxyethyl methacrylate), which show equal power conversion efficiency to their glass substrate-based counterparts. We use a novel method of including smectic liquid crystal (7-dioctyl[1]benzothieno[3,2- b][1]benzothiophene, C8-BTBT) as a crystal phase regulator in the heterojunction donor:acceptor polymer system to maintain the disposable organic solar cell efficiency without pre- or post-thermal annealing. The results show strong promise not only for more sustainable solar-cell fabrication but also as disposable and biocompatible solar cells for self-powered (energy harvesting) wearable and biomedical devices.
... The first involves the complex and costly modification of the donor or acceptor molecular structure. [15][16][17] The second approach involves the introduction of high-boiling-point solvent additives to prolong the crystallization time of the active layer thin film. [18][19][20] However, these solvent additives are typically small molecules and primarily affect the crystallinity of non-fullerene small-molecule acceptors, with minimal effect on polymer donors. ...
Achieving a more balanced charge transport by morphological control is crucial in reducing bimolecular and trap‐assisted recombination and enhancing the critical parameters for efficient organic solar cells (OSCs). Hence, a facile strategy is proposed to reduce the crystallinity difference between donor and acceptor by incorporating a novel multifunctional liquid crystal small molecule (LCSM) BDTPF4‐C6 into the binary blend. BDTPF4‐C6 is the first LCSM based on a tetrafluorobenzene unit and features a low liquid crystal phase transition temperature and strong self‐assembly ability, conducive to regulating the active layer morphology. When BDTPF4‐C6 is introduced as a guest molecule into the PM6 : Y6 binary, it exhibits better compatibility with the donor PM6 and primarily resides within the PM6 phase because of the similarity‐intermiscibility principle. Moreover, systematic studies revealed that BDTPF4‐C6 could be used as a seeding agent for PM6 to enhance its crystallinity, thereby forming a more balanced and favourable charge transport with suppressed charge recombination. Intriguingly, dual Förster resonance energy transfer was observed between the guest molecule and the host donor and acceptor, resulting in an improved current density. This study demonstrates a facile approach to balance the charge mobilities and offers new insights into boosting the efficiency of single‐junction OSCs beyond 20 %.
... To further investigate the detailed donor/acceptor phase segregation morphology features of the blend films from SMA to GMAs and to PSMA with the gradually increased SMA subunits, the photoinduced force microscopy (PiFM) measurement was carried out to distinguish the donor and acceptor at nanometer scale and provide a desired contrast for chemical imaging with high spatial resolution for these blend films 49,50 . Owing to the similar chemical structure of these acceptors, their Fourier transform infrared (FTIR) absorption spectra are also similar, and they share the same characteristic peak of the acceptor components. ...
Series of giant molecule acceptors DY, TY and QY with two, three and four small molecule acceptor subunits are synthesized by a stepwise synthetic method and used for systematically investigating the influence of subunit numbers on the structure-property relationship from small molecule acceptor YDT to giant molecule acceptors and to polymerized small molecule acceptor PY-IT. Among these acceptors-based devices, the TY-based film shows proper donor/acceptor phase separation, higher charge transfer state yield and longer charge transfer state lifetime. Combining with the highest electron mobility, more efficient exciton dissociation and lower charge carrier recombination properties, the TY-based device exhibits the highest power conversion efficiency of 16.32%. These results indicate that the subunit number in these acceptors has significant influence on their photovoltaic properties. This stepwise synthetic method of giant molecule acceptors will be beneficial to diversify their structures and promote their applications in high-efficiency and stable organic solar cells.
... Organic solar cells (OSCs) are strong candidates for green energy conversion because of their light weight, flexibility, and solution processing characteristics. [1][2][3] With the appearance of Y-series nonfullerene acceptors (NFAs) [4][5][6][7][8] and the development of device engineering, [9][10][11][12][13][14][15][16][17] the power conversion efficiency(PCE) of OSCs has exceeded 19%. [18,19] The active layer morphology plays a key role in photoelectric conversion, which includes exciton generation, transfer and dissociation, carrier migration, and charge recombination behaviors. ...
The sequential deposition process has demonstrated the great possibility to achieve a photolayer architecture with an ideal gradient phase separation morphology, which has a vital influence on the physical processes that determine the performance of organic solar cells (OSCs). However, the controllable preparation of pseudo‐planar heterojunction (P‐PHJ) with gradient distribution has not been effectively elucidated. Herein, we have proposed a binary‐dilution strategy, the PM6 solution with micro acceptor BO‐4Cl and the L8‐BO solution with micro donor PM6 respectively, to form P‐PHJ film. This architecture exists good donor (D) and acceptor (A) vertical gradient distribution and larger D/A interpenetrating regions, which promotes exciton generation and dissociation, shortens charge transport distance and optimizes carrier dynamics. Moreover, the dilution of PM6 by BO‐4Cl promotes the regulation of active layer aggregation size and phase purity, thus alleviating energy disorder and voltage loss. As a result, the P‐PHJ device exhibits an outstanding power conversion efficiency of 19.32% with an excellent short‐circuit current density of 26.92 mA cm ⁻² , much higher than planar binary heterojunction (17.67%) and ternary bulk heterojunction (18.49%) devices. This research proves a simple but effective method to provide an avenue for constructing desirable active layer morphology and high‐performance OSCs.
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... favorable vertical components distributions to enable efficient charge transport toward electrodes [20][21][22][23][24][25] . ...
Conjugated polymers are generally featured with low structural order due to their aromatic and irregular structural units, which limits their light absorption and charge mobility in organic solar cells. In this work, we report a conjugated molecule INMB-F that can act as a molecular bridge via electrostatic force to enhance the intermolecular stacking of BDT-based polymer donors toward efficient and stable organic solar cells. Molecular dynamics simulations and synchrotron X-ray measurements reveal that the electronegative INMB-F adsorb on the electropositive main chain of polymer donors to increase the donor-donor interactions, leading to enhanced structural order with shortened π-π stacking distance and consequently enhanced charge transport ability. Casting the non-fullerene acceptor layer on top of the INMB-F modified donor layer to fabricate solar cells via layer-by-layer deposition evidences significant power conversion efficiency boosts in a range of photovoltaic systems. A power conversion efficiency of 19.4% (certified 18.96%) is realized in PM6/L8-BO binary devices, which is one of the highest reported efficiencies of this material system. The enhanced structural order of polymer donors by INMB-F also leads to a six-fold enhancement of the operational stability of PM6/L8-BO organic solar cells.
... The HOMO and LUMO energy levels (E HOMO /E LUMO ) of B1-4 were estimated from E ox and E red , respectively, using the following equation: E HOMO/LUMO = À e (E ox/red + 4.8) [eV]. [25] The energy level configurations of B1-4 and major OPV materials, PC 61 BM [2a] and PTB7-Th, [26] are shown in Figure 4. The HOMO-LUMO energies were 1.90, 1.92, 1.90, and 1.70 eV for B1-4, respectively, similar to the E gap values determined from the UV/ Vis absorption spectra of thin films. ...
... 178.49 ppm;IR (KBr): v˜= 1610, 1594, 1513, 1477, 1447, 1362, 1248, 1091, 751 cm À 1 ; UV/Vis (CHCl 3 ): λ max (ɛ) = 513 nm (57,000 M À 1 cm À 1 ); APCI MS: m/z (%): 682.26 (25) H 4.27, N 3.49; found: C 69.29, H 4.06, N 3.38. ...
Three donor−acceptor−donor dioxaborin compounds containing carbazoles as the terminal electron donor groups were synthesized. Their electronic and photovoltaic properties were compared with those of an analog with terminal triphenylamine groups. The HOMO and LUMO levels of the N‐phenylcarbazole derivative were 0.3 and 0.1 eV lower, respectively, than those of the triphenylamine analog. During the evaluation of organic photovoltaic characteristics, the N‐phenylcarbazole derivative exhibited a power conversion efficiency (PCE) of 2.06 % when combined with a conducting polymer (PTB7‐Th). Contrarily, the triphenylamine analog exhibited a PCE of 2.85 % when combined with a fullerene acceptor (PC61BM). The results showed that the N‐phenylcarbazole and triphenylamine derivatives functioned as electron acceptor and donor materials, respectively. The conversion from the electron donor to the acceptor was achieved via a slight change in the structure of the terminal donor groups of the dioxaborin compounds. This study will prove valuable for the development of nonfullerene acceptors.
... [4] Nevertheless, the uncertainty of batch-to-batch variability and inferior PCEs compared to their SMA counterparts inevitably hamper the development of all-polymer solar cells (all-PSCs). [5] As a result, it is imperative to explore the alternative acceptors in order to acquire high-performance and stable OSCs. ...
Oligomer acceptors have recently emerged as promising photovoltaic materials for achieving high power conversion efficiency (PCE) and long‐term stability in organic solar cells (OSCs). However, the limited availability of diverse acceptors, resulting from the sole synthetic approach, has hindered their potential for future industrialization. In this study, we present a facile and effective stepwise approach that utilizes two consecutive Stille coupling reactions for the synthesis of oligomer acceptors. To demonstrate the feasibility of the novel approach, we successfully synthesize a trimer acceptor, Tri‐Y6‐OD, and further systematically investigate the impact of oligomerization on device performance and stability. The results reveal that this approach has significant advantages compared to the conventional method, including reduced formation of unwanted by‐products and lower difficulties in purification. Remarkably, the OSC based on PM6 : Tri‐Y6‐OD achieves an impressive PCE of 18.03 % and maintains 80 % of the initial PCE (T80) for 1523 h under illumination, surpassing the performance of the corresponding small molecule acceptor Y6‐OD‐based device. Furthermore, the versatility of the synthetic strategy in obtaining diverse acceptors is further demonstrated. Overall, our findings provide a facile, versatile and stepwise way for synthesizing oligomer acceptors, thereby facilitating the development of stable and efficient OSCs.
... Due to the unique advantages of light weight, low cost, flexible and large area manufacturing [1][2][3][4][5][6][7][8][9], PSCs have aroused broad attentions in the past several decades. Benefit from the fast development of new synthesized photovoltaic materials, especially the emergence of nonfullerene acceptors materials in the recent years [10][11][12][13][14][15][16][17], PSCs based on non-fullerene acceptors have achieved great development relative to those based on fullerene acceptors. Apart from the fast development in photoactive materials, huge breakthroughs have also been made in the area of morphology optimization and advanced device fabrication techniques [18][19][20][21][22][23]. ...
... To investigate the effect of block copolymer PS-b-PAA on photovoltaic performance, an efficient device is fabricated. The prepared PSCs with the conventional devices structure of ITO/PEDOT:PSS/active layer/PFN-Br/Al, in which ITO = indium tin oxide; PEDOT:PSS = poly (3,4-ethylenedioxythiophene):polystyrene sulfonate; PFN-Br = Poly ((9,9-bis(3′-(N,N-dimethyl)-Nethylammoinium-propyl-2,7-fluorene)alt-2,7-(9,9-dioctylfluorene))dibromide), are shown in Fig. 1d [10,50], photovoltaic materials PM6 and IT-4F are chose as the electron donor and electron acceptor respectively. The control group was also fabricated under the same condition as a comparison. ...
Additive treatment is an effective method for manipulating the bulk heterojunction (BHJ) photoactive layer morphology of polymer solar cells (PSCs). In this work, block copolymer, polystyrene-block-poly(acrylic acid) (PS-b-PAA), was elaborately selected (according to Flory-Huggins theory) as an additive for active layer to manipulate the BHJ morphology and to enhance the photovoltaic performance of devices. As results, with a PS-b-PAA concentration of 0.4 mg/ml, the corresponding devices achieve a significant power conversion efficiency (PCE) improvement to 13.08%. By systematically analysis, the improved PCE can be ascribed to more appreciate phase separation induced by incorporation of PS-b-PAA. For the instance of the photovoltaic physical process, more suitable morphology can induce improved charge transport efficiency, suppressed bimolecular recombi-nation and monomolecular recombination or trap-assisted recombination. In comparing, the photovoltaic performance of devices with PS-b-PAA is obviously better than that of devices with insulating polymer polystyrene (PS) and polyacrylic acid (PAA). Hence, this work checks the morphology manipulation effects of block copol-ymer PS-b-PAA and provides an effective and facile method to improve the morphology and photovoltaic performances of PSCs.
... Besides, PM6-TTO-10:Y6 showed the maximum generation intensity of the donor's GSB signal ( Figure 8d and Table S8, Supporting Information). This may be related to the better miscibility and the optimized fibrous interpenetrating network structure, [30] leading to an enhancement of the hole transfer and charge-carrier generation efficiency, thus resulting in the highest PCE and J SC of the device. ...
For the first time, we combined terpolymerization and regioisomerization strategies to develop novel polymer donors to overcome the difficulty of improving organic solar cells (OSCs) performance. Two novel isomeric units, TTO and TTI, were obtained and incorporated into the PM6 backbone via random copolymerization to form a series of terpolymers. Interestingly, we found that different chlorine (Cl) substituent positions can significantly change the molecular planarity and electrostatic potential (ESP) owing to the steric hindrance effect of the heavy Cl atom, which leads to different molecular aggregation behaviors and miscibility between the donor and acceptor. The TTO unit features a higher number of multiple S⋅⋅⋅O non-covalent interactions, more positive ESP, and fewer isomer structures than TTI. As a result, the terpolymer PM6-TTO-10 exhibited a much better molecular coplanarity, stronger crystallinity, more obvious aggregation behavior, and proper phase separation in the blend film, which are conducive to more efficient exciton dissociation and charge transfer. Consequently, the PM6-TTO-10:BTP-eC9-based OSCs achieved a champion power conversion efficiency (PCE) of 18.37% with an outstanding fill factor of 79.97%, which are among the highest values reported for terpolymer-based OSCs. This work demonstrates that terpolymerization combined with Cl regioisomerization is an efficient approach for achieving high-performance polymer donors. This article is protected by copyright. All rights reserved.
... Generally, TA treatment aims to facilitate molecular crystallization and thus results in phase separation. [41] Due to the better solubility and fluidity of small molecules compared with polymer molecules, it is difficult to form pre-aggregation like polymer, and therefore the nanoscale phase separation morphology and PCEs before and after annealing are significantly different. Though TA treatment has been regarded as an effective process to promote crystallization and phase separation, the annealing mechanism of the active layer morphology of all small molecules and the dynamic change of the active layer morphology with annealing temperature are rarely discussed. ...
Achieving an ideal morphology to realize efficient charge generation and transport is an imperative avenue to improve the photovoltaic performance of all small‐molecule organic solar cells (SM‐OSCs). Here, ternary SM‐OSCs are fabricated based on a new small molecule donor, SM‐mB, and an alloyed blend acceptor of Y6 and its derivative, L8‐BO, and desirable hierarchical morphology with appropriate nanoscale phase separation is successfully realized through adjusting the thermal annealing treatment conditions and compositions of mixed acceptors in the active layer. Then the ternary SM‐OSCs achieve an excellent PCE of 17.06 %, which is one of the best results for the SM‐OSCs so far. The desirable morphology can be ascribed to the optimization of the miscibility‐driven donor and acceptor blend morphology that takes full advantage of the individual advantages of both acceptors, which facilitate efficient charge generation and extraction with more balanced charge carrier mobilities. More importantly, the photovoltaic performance of the ternary SM‐OSCs possesses a high tolerance to the device fabrication conditions, including thermal annealing treatment, and is insensitive to film thickness, which is beneficial for large‐area manufacture and future practical applications.
