Donor Copolymers Research Articles

Advances in Blade-Coated Organic Photovoltaics

Organic photovoltaics (OPVs) are a type of solar cell technology that uses organic semiconducting materials to convert sunlight into electricity. Unlike traditional silicon-based solar cells, OPVs are lightweight, flexible, and can be fabricated using cost-effective solution-processing techniques such as blade coating, enabling large-area device fabrication and is compatible with roll-to-roll manufacturing, making it ideal for OPV production. However, key challenges for OPVs, such as achieving high efficiency and scalability, maintaining film uniformity, enhancing material stability, optimizing processing techniques, mitigating environmental and health impacts, improving charge transport and reducing recombination losses, and overcoming performance degradation in large-area production are still under investigation. Recent developments include high-efficiency copolymer donors, ternary additives for optimized morphology, and the integration of novel interlayers and electrodes. Scalable processes such as accelerated blade coating and green solvents like o-methylanisole are also explored, highlighting their role in enhancing efficiency, stability, and sustainability. Additionally, insights into nanoparticle additives, solvent engineering, and molecular design underscore the potential for blade-coated OPVs to achieve high performance while maintaining environmental compatibility. These advancements collectively address challenges in efficiency and scalability, paving the way for OPVs to meet industrial demands and contribute to a greener energy landscape.

Wide bandgap polymer donors with an acceptor1-π-acceptor2-π configuration for efficient polymer solar cells

To maximize the photovoltaic performance of polymer solar cells (PSCs), polymer donors and nonfullerene acceptors (NFAs) should be designed with complementarily optical and electronic properties as well as desirable morphological features. Currently, high-performance polymer donors are mainly constructed by alternating copolymerization of electron-rich (D) and electron-deficient (A) units. Here, we demonstrate that acceptor1-π-acceptor2-π (A1-π-A2-π)-type polymer donors constructed by copolymerization of two different A units can achieve comparable photovoltaic properties with those of D-π-A-π-type counterparts. By using the ladder-type 4,10-bis(2-hexyldecyl)-thieno[2ˊ,3ˊ:5,6]pyrido[3,4-g]thieno-[3,2-c]isoquinoline-5,11-dione as A1 unit, difluorobenzotriazole or benzodithiophene-4,8-dione as A2 unit, and thiophene unit as the π bridge, two A1-π-A2-π-type copolymers, P03 and P07, are successfully synthesized. Due to the weakened intramolecular charge-transfer effect, P03 and P07 exhibit wide bandgaps of 1.88 and 1.74 eV, respectively. In combination with the NFA of L8-BO, the P03:L8-BO-based blend shows superior crystallinity and uniform phase-separated morphology thereby leading to a higher power conversion efficiency (PCE) of 15.03 % in comparison with the P07:L8-BO-based blend which shows a PCE of 9.84 %. Notably, the 15.03 % efficiency is by far the highest value for PSCs based on A1-π-A2-π-type polymer donors. These results provide useful guidance for the future design of high-performance donor copolymers for PSCs.

Efficient triisopropylsilylethynyl-substituted benzo[1,2-b:4,5-b′]dithiophene-based random terpolymers enable non-fullerene organic solar cells with enhanced efficiency

Recent work has highlighted the pivotal role of ternary random polymers in the development of efficient high-performance polymer donors for organic solar cells (OSCs) and most of these D-A copolymer donors are so far constituted of an equal proportion of D and A-units. In this contribution, we report series of PM6-based ternary random terpolymers with unequal D- and A-units, namely, PM-TIPS10, PM-TIPS20 and PM-TIPS20, respectively by adding the 10%, 20% and 30% of simple and low-cost triisopropylsilylethynyl-substituted benzo[1,2-b:4,5-b′]dithiophene (BDT-TIPS) unit as second donor (D1) unit in polymer backbone based on D1-A-D2-A molecular design. Ascribed from the structural similarity of the two building blocks in the terpolymer backbone, these polymers showed orderly molecular packing, broadened light absorption, and the face-on orientation of the active layer to facilitate charge transport. Additionally, the new polymers displayed much deeper highest occupied molecular orbital (HOMO) energy levels than host PM6 polymer, which helped in enhancing the open circuit voltage (Voc) in the PM-TIPS-based OSCs. As a result, when combined with BTP-eC9 acceptor unit, PM-TIPS10 and PM-TIPS20 displayed best efficiency of 16.7 and 16.5% with a small energy loss of 0.484 and 0.473 eV, producing overall superior device parameters compared to PM6-based devices tested parallelly (PCE of 15.7%). This study reveals the correlation between introduction of the BDT-TIPS unit on polymer properties and photovoltaic performance and thus contributes to the design of high-PCE polymer donors by adapting a ternary random copolymerization strategy.

High‐Performance Terpolymers with Well‐Defined Structures Facilitate PCE Over 19% for Polymer Solar Cells

AbstractTernary copolymerization is a cost‐effective and time‐saving approach to improve device performance and batch stability of polymer donors. However, the structure of the ternary polymer donor obtained by the traditional one‐pot polymerization is vague due to the different monomer reaction order, which has a great influence on the absorption, crystallization, molecular stacking, and device performance. Therefore, it is necessary to obtain terpolymers with definite structures, and systematically study the differences in device properties of polymers with different sequence structures. Herein, three terpolymers D1, D2, and D3 are developed. Random copolymer D3 is obtained via the traditional one‐pot method while alternating copolymer donor D1 and block copolymer D2 are synthesized by stepwise polymerization. Because the block copolymer D2 possess periodic sequence distribution and retains the excellent properties of the two polymer matrix very well, the D2‐based device shows enhanced tightened π‐face‐on molecular stacking, distinguished efficient exciton dissociation, and decreased energy loss. As a result, the D2:L8‐BO‐based polymer solar cells achieve one of a record power conversion efficiency of 19.03%. The work demonstrates changing the sequence structure of the polymers to synthesize well‐defined structures polymer donors not only maintains the features of polymer matrix, but also combines the advantages of ternary copolymerization.

The Challenges of Using Block Copolymers for Organic Solar Cells and Identifying the Most Suitable Approaches

For organic solar cells, a variety of materials are employed, including homopolymer donors and D-A copolymer donors. Organic solar cells are made from Pb (or Sn) halide perovskites, although they have some flaws. A mineral that resembles salt and is present in Pb perovskites quickly dissolves in moisture or water. It may have an impact on your health. The instability of Sn halide perovskites prevents them from becoming suitable. Perovskites are extremely vulnerable to oxidation on their own. Therefore, organic solar cells require a new substance. The usage of block copolymers as a component in organic solar cells is the main topic of this article. The quantum efficiency of organic solar cells will increase by modifying the block copolymer's shape and choosing the right material.

Trifluoromethylation in the Design and Synthesis of High-Performance Wide Bandgap Polymer Donors for Quasiplanar Heterojunction Organic Solar Cells.

New strategies for the molecular design to construct efficient electron-deficient units for D-A-type donor copolymers are urgently needed. Halogenation of electron-deficient units (A) has been shown to be the most effective strategy reported to date with which to produce high-performance donor polymers. Herein, we have constructed two different trifluoromethyl-substituted polymer donors, PBQP-CF3 and PBQ-CF3. The trifluoromethylation process typically involves complex protocols, which are not widely used in the synthesis of polymer donors. Accordingly, we have developed a single-step, one-pot synthesis of the new trifluoromethyl-substituted electron-deficient unit (A) of PBQ-CF3. The strong electron-withdrawing ability of the trifluoromethyl group ensures deeper highest occupied molecular orbital (HOMO) energy levels, and the non-covalent bonding interactions of the fluorine atoms are beneficial to the regulation of aggregation properties. Thus, both of the trifluoromethyl-substituted polymer donors obtained much higher power conversion efficiency (PCE) than PBDP-H (6.66%). PBQ-CF3 exhibits a deeper HOMO energy level, better aggregation behavior, and higher hole mobility than PBQP-CF3. PBQ-CF3-based quasiplanar heterojunction (Q-PHJ) devices therefore achieve simultaneously enhanced open-circuit voltage (VOC), short-circuit current density (JSC), and fill factor (FF) and an impressive PCE (16.02%), which is much higher than that obtained by PBQP-CF3-based devices (12.57%). This work reveals a promising path to synthesis of the trifluoromethylation polymer donors and demonstrates that the trifluoromethylation strategy can be used to enhance the photovoltaic performance.

Long-Range Charge Separation Enabled by Intramoiety Delocalized Excitations in Copolymer Donors in Organic Photovoltaic Blends.

For over two decades, most high-performance organic photovoltaics (OPVs) have been made with donor:acceptor bulk heterojunctions with domain sizes limited by exciton diffusion, where charge separation mostly takes place through the dissociation of the interfacial charge-transfer (xCT) excitons. Recently, nonfullerene acceptor (NFA)-based OPVs have shown excellent compatibility to device structures with large domains in active layers. However, it remains elusive how the excitations that are distant from the interfaces are converted into free charges. Here, we report the identification of a new charge separation channel in model copolymer/NFA blends mediated by intra-moiety delocalized excitations in both planar heterojunctions and donor-enriched bulk heterojunctions. The delocalized excitations induced by interchromophore electronic interactions in copolymer donors mediate the long-range charge separation and dissociate into free charges without forming the bound xCT states first, releasing the constraints associated with the short exciton diffusion length in organic materials. The long-range charge separation mechanism uncovered in this work, in cooperation with the short-range xCT-mediated pathway, holds the potential to further optimize OPVs with diverse device structures.

Improvement of photovoltaic properties of benzo[1,2-b:4,5-b′]difuran-conjugated polymer by side-chain modification

The development of polymer solar cells (PSCs) for the donor materials based on benzo[1,2-b:4,5-b′]dithiophene (BDT) has significantly boosted the power conversion efficiency (PCE). However, the PCE of polymer donor materials for benzo[1,2-b:4,5-b′]difuran (BDF)-based lags far behind that of their BDT analogs. To further explore efficient copolymers based on BDF units, a two-dimensional (2D) side-chain strategy was proposed to investigate the atom-changing effects on the copolymer donors for the properties of electron and optical. In this study, we designed and synthesized three new BDF-based copolymer donor materials, named PBDF-C, PBDF-O, and PBDF-S. Owing to the balanced charge transport and favorable phase separation of PBDF-S:Y6, a high PCE of 13.4%, a short-circuit current ( J sc ) of 25.48 mA cm −2 , an open-circuit voltage ( V oc ) of 0.721 V, and a fill factor (FF) of 72.6% was obtained. This research demonstrates that the BDF building block has great potential for constructing conjugated copolymer donors for high-performance PSCs and that 2D side-chain modification is a facile approach for designing high-performance BDF-based copolymer materials.

Extension A unit in D-A polymer donor leads to higher JSC and FF for non-fullerene organic solar cells

Two copolymer donors based on the thiophene-vinylene-thiophene (TVT) and thieno[3,2-b]thiophene-vinylene-thieno[3,2-b]thiophene (TTVTT) derivative, which were denoted as VT and VDT, respectively, were synthesized and applied to organic solar cells (OSCs). Detailed investigations revealed that the extension of conjugation can affect the optical and electronic properties, molecular aggregation, charge separation in the bulk-heterojunction films, and thus the overall photovoltaic performances. Without any additives or post-solvent/thermal annealing processes, the OSCs based on VDT: Y6 and VT: Y6 exhibited optimal power conversion efficiencies (PCEs) of 12.67% and 8.85%, respectively. These results indicate that extending the π-electron delocalization of the copolymer donors to broaden the absorption range and enhance intermolecular packing is an effective strategy to promote the device's performances.

Poly(dimethylsiloxane)-block-PM6 Polymer Donors for High-Performance and Mechanically Robust Polymer Solar Cells.

High power conversion efficiency (PCE) and stretchability are the dual requirements for the wearable application of polymer solar cells (PSCs). However, most efficient photoactive films are mechanically brittle. In this work, highly efficient (PCE = 18%) and mechanically robust (crack-onset strain (COS) = 18%) PSCs are acheived by designing block copolymer (BCP) donors, PM6-b-PDMSx (x = 5k, 12k, and 19k). In these BCP donors, stretchable poly(dimethylsiloxane) (PDMS) blocks are covalently linked with the PM6 blocks to effectively increase the stretchability. The stretchability of the BCP donors increases with a longer PDMS block, and PM6-b-PDMS19k :L8-BO PSC exhibits a high PCE (18%) and 9-times higher COS value (18%) compared to that (COS = 2%) of the PM6:L8-BO-based PSC. However, the PM6:L8-BO:PDMS12k ternary blend shows inferior PCE (5%) and COS (1%) due to the macrophase separation between PDMS and active components. In the intrinsically stretchable PSC, the PM6-b-PDMS19k :L8-BO blend exhibits significantly greater mechanical stability PCE80% ((80% of the initial PCE) at 36% strain) than those of the PM6:L8-BO blend (PCE80% at 12% strain) and the PM6:L8-BO:PDMS ternary blend (PCE80% at 4% strain). This study suggests an effective design strategy of BCP PD to achieve stretchable and efficient PSCs.

Halogen-Free Donor Polymers Based on Dicyanobenzotriazole with Low Energy Loss and High Efficiency in Organic Solar Cells.

Halogenation of organic semiconductors is an efficient strategy for improving the performance of organic solar cells (OSCs), while the introduction of halogens usually involves complex synthetic process and serious environment pollution problems. Herein, three halogen-free ternary copolymer donors (PCNx, x= 3, 4, 5) based on electron-withdrawing dicyanobenzotriazole are reported. When blended with the Y6, PCN3 with strong interchain interactions results in appropriate crystallinity and thermodynamic miscibility of the blend film. Grazing-incidence wide-angle X-ray scattering measurements indicate that PCN3 has more ordered arrangement and stronger π-π stacking than previous PCN2. Fourier-transform photocurrent spectroscopy and external quantum efficiency of electroluminescence measurements show that PCN3-based OSCs have lower energy loss than PCN2, which leads to their higher open-circuit voltage (0.873V). The device based on PCN3 reaches power conversion efficiency (PCE) of 15.33% in binary OSCs, one of the highest values for OSCs with halogen-free donor polymers. The PCE of 17.80% and 18.10% are obtained in PM6:PCN3:Y6 and PM6:PCN3:BTP-eC9 ternary devices, much higher than those of PM6:Y6 (16.31%) and PM6:BTP-eC9 (17.33%) devices. Additionally, this ternary OSCs exhibit superior stability compared to binary host system. This work gives a promising path for halogen-free donor polymers to achieve low energy loss and high PCE.

Enhanced Photovoltaic Performances via Chlorine Substitution on Alkylphenyl Side Chains of a Conjugated Polymer

Owing to the enhanced intermolecular interaction, aromatically chlorinated polymers have been energetic to the molecular design and innovation of π-conjugated polymers for efficient organic solar cells (OSCs). Herein, two structurally similar copolymer donors (Z1 and Z2) based on benzodithiophene (BDT) on alkylbenzene conjugated side chains without and with chlorine atoms were designed and synthesized. Two copolymers possessed similar absorption spectra ranging from 380 to 620 nm and approximated optical band gap (Egopt). Compared with the nonchlorinated polymer Z1, polymer Z2 substituted by chlorine in the meta-position of the alkylphenyl group endowed it an enhanced π–π stacking and favorable morphology, which brought the OSCs the significantly enhanced photocurrent and fill factor as well as hole/electron mobility. When the nonchlorinated copolymer Z1 showed a power conversion efficiency (PCE) of 12.03%, the chlorinated copolymer Z2 obtained a higher PCE of 15.11%. The results provide more insight into the role of the chlorinated alkylphenyl side chains in designing new conjugated polymers to promote the performance of OSCs.

High-Performance D–A Copolymer Donor Based on Difluoroquinoxaline A-Unit with Alkyl-Chlorothiophene Substituents for Polymer Solar Cells

Open AccessCCS ChemistryRESEARCH ARTICLES15 Dec 2022High Performance D-A Copolymer Donor Based on Difluoroquinoxaline A-unit with Alkyl-chlorothiophene Substituents for Polymer Solar Cells Can Zhu, Ke Hu, Lei Meng, Xiaolei Kong, Wenbin Lai, Shucheng Qin, Beibei Qiu, Jinyuan Zhang, Zhanjun Zhang, Yilei Wu, Xiaojun Li and Yongfang Li Can Zhu Google Scholar More articles by this author , Ke Hu Google Scholar More articles by this author , Lei Meng Google Scholar More articles by this author , Xiaolei Kong Google Scholar More articles by this author , Wenbin Lai Google Scholar More articles by this author , Shucheng Qin Google Scholar More articles by this author , Beibei Qiu Google Scholar More articles by this author , Jinyuan Zhang Google Scholar More articles by this author , Zhanjun Zhang Google Scholar More articles by this author , Yilei Wu Google Scholar More articles by this author , Xiaojun Li Google Scholar More articles by this author and Yongfang Li Google Scholar More articles by this author https://doi.org/10.31635/ccschem.022.202202491 SectionsSupplemental MaterialAboutPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Side chain engineering with fluorine substitution is widely used in enhancing photovoltaic performance of polymer donors in the research field of polymer solar cells (PSCs). However, fluorine substitution has the disadvantages of complicated synthesis and high cost. Here, we synthesized a novel D-A copolymer donor PBQ9 based on difluoroquinoxaline A-unit with chlorine substitution on its alkyl-thiophene side chains instead of fluorine substitution in the polymer donor PBQ6, which greatly shortens the synthetic route and reduces the cost. Interestingly, the optimized binary PSC with PBQ9 as polymer donor and m-TEH as acceptor demonstrated a high power conversion efficiency (PCE) of 18.81% (certified PCE of 18.33% by National Institute of Metrology (NIM), China) with a high fill factor (FF) of 80.59%, and the photovoltaic performance of the PSCs is insensitive to the different batches of the polymer donor. The results indicate that PBQ9 is a high-performance polymer donor and the chlorine substitution is an effective strategy for improving photovoltaic performance and reducing cost of the polymer donors. Download figure Download PowerPoint Previous articleNext article FiguresReferencesRelatedDetails Issue AssignmentVolume 0Issue jaPage: 1-43Supporting Information Copyright & Permissions© 2022 Chinese Chemical Society Downloaded 83 times PDF downloadLoading ...

Asymmetric fluorine and chlorine side-chain engineered quinoxaline-based D–A copolymer for both fullerene and nonfullerene polymer solar cells

A novel copolymer donor (Qx) based quinoxaline with asymmetric side chains, namely PBDTTS-2FClQx, is synthesized. The PCE of optimized ternary OSC (PBDTTS-2FClQx:Y6:PC71BM = 1 : 0.9 : 0.1) is 13.59%, but binary PBDTTS-2FClQx:Y6 (12.41%).

A tetracyclic-bislactone-based copolymer donor for efficient semitransparent organic photovoltaics

A copolymer donor PBDTTPTP based on a tetracyclic bislactone unit achieved a high light utilization efficiency of 4.38% in semitransparent organic photovoltaics.

Terpolymer Donor with Inside Alkyl Substituents on Thiophene π-Bridges toward Thiazolothiazole A2 -Unit Enables 18.21% Efficiency of Polymer Solar Cells.

PM6 is a widely used D-A copolymer donor in the polymer solar cells (PSCs). Incorporating second electron-withdrawing (A2 ) units into PM6 backbone by ternary D-A1 -D-A2 random copolymerization strategy is an effective approach to further improve its photovoltaic performance. Here, the authors synthesize the PM6-based terpolymers by introducing thiazolothiazole as the A2 units connecting with thiophene π-bridges attaching alkyl substituent towards the A2 unit (PMT-CT) or towards D-unit (PMT-FT), and study the effect of the alkyl substituent position on the photovoltaic performance of them. Two terpolymers PMT-FT-10 and PMT-CT-10 are obtained by incorporating 10% A2 units in the terpolymers. The film of PMT-CT-10 shows slightly up-shifted highest occupied molecular orbital (HOMO) energy levels while better co-planar structure than that of PMT-FT-10. Meanwhile, the PMT-CT-10:Y6 blend film exhibits better molecular packing properties, more proper phase separation and more balanced hole and electron mobilities, which are beneficial to more efficient exciton dissociation, efficient charge transport and weaker bimolecular recombination. Consequently, the PMT-CT-10 based PSCs obtain the highest power conversion efficiency of 18.21%. The results indicate that side chain position on the thiophene π-bridges influence the device performance of the terpolymer donors, and PMT-CT-10 is a high efficiency polymer donor for the PSCs.

High‐Efficiency Semi‐Transparent Organic Solar Cells Using Pentacyclic Aromatic Lactam‐Containing Terpolymer Strategy for Eco‐Friendly Greenhouse Application

Semitransparent organic solar cells (ST‐OSCs) offer unique features such as spectral tunability and see‐through function, giving them great potential in photovoltaic (PV) agriculture. However, the combination of sufficient average visible transmittance (AVT) and high power conversion efficiency (PCE) with eco‐friendly device fabrication has always been a key issue. Herein, a simple but effective strategy by incorporating pentacyclic aromatic lactam acceptor unit (TPTI) in copolymer donors for toluene processed high‐efficiency ST‐OSCs is performed. The comparisons between D18‐ and DEH‐X‐based ST‐OSCs demonstrate the effect of TPTI inserting on the polymer main skeleton can not only lower the energy level, improve the processability in nonhalogen solvent, tune the ideal morphology for efficient charge dissociation, but also control a photon transport window suitable for plant absorption. Therefore, the resulting OSCs processed with toluene exhibit a PCE of 14.6% with an AVT of 22%, which represents one of the highest values for ST‐OSCs made from nonhalogenated solvents. What's more, it is found that plant growth under ST‐OSCs filtered light is comparable with that under natural light. Herein, a guide for developing high‐performance ST‐OSCs is provided and the prospect of ST‐OSCs for green manufacturing PV greenhouse application is demonstrated.

A simple structure copolymer donor based on carboxylated benzodithiophene for polymer solar cells

A simple structure copolymer donor based on carboxylated benzodithiophene for polymer solar cells

New wide band gap π-conjugated copolymers based on anthra[1,2-b: 4,3-b': 6,7-c''] trithiophene-8,12-dione for high performance non-fullerene polymer solar cells with an efficiency of 15.07 %

Developing efficient wide-bandgap copolymer donor materials to match with narrow bandgap non-fullerene acceptors is continuously ongoing for polymer solar cells. Herein, two new D-A copolymers are designed and synthesized by embedding the same anthra[1,2-b:4,3-b':6,7-c"] trithiophene-8,12-dione (A3T) acceptor unit and different donor units, i.e., BDTTZ ( P126 ) and BDTTh ( P127 ). These copolymers showed broad absorption from 350 to 680 nm and deeper HOMO energy level. We have used these two copolymers as donors and a narrow bandgap non-fullerene acceptor Y6 to prepare bulk heterojunction polymer solar cells (PSCs). After the optimization, P126 :Y6 and P127 :Y6 attained overall power conversion efficiency of 15.07% and 12.27%, respectively. The higher PCE for the P126 than P127 is associated with the more efficient photon harvesting and photogenerated excitons, balanced charge transport, and low energy loss. Our results may help to design new polymers with a deeper highest occupied molecular orbital level that will be well-matched with non-fullerene acceptors. • We have used the approach of weak donor and strong acceptor approach to design the D-A copolymers. • Two D-A copolymers were designed with same A3T acceptor and different donors, i.e., BDTTZ ( P126 ) and BDTTh (P127 ). • Both the copolymers showed deeper HOMO energy level to achieved high V OC . • P126 :Y6 and P127 :Y6 showed power conversion efficiency of 15.07% and 12.27%, respectively.

18.55% Efficiency Polymer Solar Cells Based on a Small Molecule Acceptor with Alkylthienyl Outer Side Chains and a Low-Cost Polymer Donor PTQ10

18.55% Efficiency Polymer Solar Cells Based on a Small Molecule Acceptor with Alkylthienyl Outer Side Chains and a Low-Cost Polymer Donor PTQ10