Ternary Organic Solar Cells Research Articles

Configurational Isomerization‐Induced Orientation Switching: Non‐Fused Ring Dipodal Phosphonic Acids as Hole‐Extraction Layers for Efficient Organic Solar Cells

AbstractPhosphonic acid (PA) self‐assembled molecules have recently emerged as efficient hole‐extraction layers (HELs) for organic solar cells (OSCs). However, the structural effects of PAs on their self‐assembly behaviors on indium tin oxide (ITO) and thus photovoltaic performance remain obscure. Herein, we present a novel class of PAs, namely “non‐fused ring dipodal phosphonic acids” (NFR‐DPAs), featuring simple and malleable non‐fused ring backbones and dipodal phosphonic acid anchoring groups. The efficacy of configurational isomerism in modulating the photoelectronic properties and switching molecular orientation of PAs atop electrodes results in distinct substrate surface energy and electronic characteristics. The NFR‐DPA with linear (C2h symmetry) and brominated backbone exhibits favorable face‐on orientation and enhanced work function modification capability compared to its angular (C2v symmetry) and non‐brominated counterparts. This makes it versatile HELs in mitigating interfacial resistance for energy barrier‐free hole collection, and affording optimal active layer morphology, which results in an impressive efficiency of 19.11 % with a low voltage loss of 0.52 V for binary OSC devices and an excellent efficiency of 19.66 % for ternary OSC devices. This study presents a new dimension to design PA‐based HELs for high‐performance OSCs.

Designing a Highly Crystalline Polymer Donor with Alkylsilyl and Fluorine Substitution to Achieve Efficient Ternary Organic Solar Cells.

Adopting a ternary strategy is an effective approach to enhance the power conversion efficiency (PCE) in organic solar cells (OSCs). Previous research on highly efficient ternary systems has predominantly focused on those based on highly crystalline dual small molecule acceptors. However, limited attention has been given to ternary systems utilizing dual polymer donors. Herein, by incorporating the fluorine and alkylsilyl substitution, a new polymer donor named PX1 is developed, which demonstrates strong crystallinity and excellent miscibility with polymer PM6. Moreover, PX1 broadens and enhances the absorption properties of the PM6:L8-BO blends, and its molecular orbital energy level is situated between those of PM6 and L8-BO, highlighting its suitability as a third component. Introducing 20% PX1 into the PM6:L8-BO system resulted in a high PCE of 18.82%. PX1 effectively suppresses charge recombination and reduces energy losses, while also serving as a morphology modulator that enhances the crystallization and improves the molecular packing order of the active layer by shortening the π-π stacking distance and extending crystalline coherence length. These factors collectively contribute to the performance improvements in ternary devices. This study demonstrates that employing a dual polymer donor strategy is a promising approach for achieving high-performance ternary OSCs.

Tetrahydrofuran Processable Organic Solar Cells with 19.45% Efficiency Realized by Introducing High Molecular Dipole Unit Into the Terpolymer.

Developing organic solar cells (OSCs) processable with halogen-free, non-aromatic solvents is crucial for practical applications, yet challenging due to the limited solubility of most photoactive materials. This study introduces high-performance terpolymers processable in tetrahydrofuran (THF) by incorporating dithienophthalimide (DPI) into the PM6 backbone. DPI extends the absorption band, lowers HOMO levels, and improves THF solubility and film crystallinity through its large dipole moment effect. Optimal PBD-10:L8-BO devices processed with THF achieved a competitive power conversion efficiency (PCE) of 18.79%, approaching chloroform-processed devices (19.04%). By introducing PBTz-F as a second donor, ternary OSCs reached an impressive 19.45% PCE when processed with THF. This improvement stems from enhanced photon generation, improved morphology, better charge transport, longer exciton lifetimes, efficient charge dissociation and collection, and suppressed recombination. These PCEs of 18.79% and 19.45% for binary and ternary blend OSCs, respectively, represent the highest reported efficiencies for OSCs processed with halogen-free, non-aromatic solvents. This work demonstrates significant progress in eco-friendly OSC fabrication, paving the way for more sustainable and commercially viable organic photovoltaic technologies.

Achieving 19.72% Efficiency in Ternary Organic Solar Cells through Electrostatic Potential‐Driven Morphology Control

AbstractThe ternary strategy has proven effective in enhancing the performance of organic solar cells (OSCs), yet identifying the optimal third component remains a challenge due to the lack of theoretical frameworks for predicting its impact based on molecular structure. This study addresses this challenge by proposing quantitative parameters derived from molecular surface electrostatic potential (ESP) as criteria for selecting ternary components. The asymmetric acceptor BTP‐OS, which exhibits a lower total average ESP and larger molecular polarization index relative to the host acceptor, is introduced into the PM6:L8‐BO system. This incorporation led to weakened ESP‐induced intermolecular interactions and reduce miscibility with donor polymer, resulting in an optimized multi‐scale morphology of the ternary blend. Consequently, the ternary device achieved an efficiency of 19.72%, one of the highest values for PM6:L8‐BO‐based ternary devices, with enhanced exciton dissociation and charge collection, lower energy disorder, and minimized non‐radiative energy losses. Comparable efficiency improvements are also verified in PM6:BTP‐eC9 and D18:N3 systems, demonstrating the broad applicability of the proposed approach. This study not only provides a practical and effective principle for selecting ternary components but also establishes a broader framework for optimizing ternary OSCs, potentially advancing the development of more efficient OSCs across diverse material systems.

Non-fused nonfullerene acceptors withasymmetric benzo[1,2-b:3,4-b', 6,5-b"]trithiophene (BTT) central donor core and different acceptor terminal units for organic solar cells.

Here in, we have designed two new unfused non-fullerene small molecules based on asymmetric benzo[1,2-b:3.4-b', 6,5-b"]trithiophene (BTT) central donor core and different terminal units, i.e. 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (NFA-4) and 1,3-diethyl-2-thioxodi hydropyrimidine-4,6(1H,5H)-dione (NFA-5) and their optical and electrochemical properties were investigated. Employing a wide band-gap copolymer D18, the binary D18: NFA-4 and D18:NFA-5 bulk heterojunction-based organic solar cells realized an overall power conversion efficiency of about 17.07% and 11.27 %, respectively. The higher value of power conversion efficiency for the NFA-4-based organic solar cells, as compared to the NFA-5 counterpart, is attributed to the enhanced values of short circuit current, open circuit voltage, and fill factor. After the incorporation of NFA-5 into the binary bulk heterojunction D18:NFA-4, the ternary organic solar cells attained a power conversion efficiency of 18.05 %, which is higher than that for the binary counterparts and attributed to the increased values of short circuit current, fill factor, and open circuit voltage. The increased value of short circuit current is associated with the effective utilization of excitons through the energy transfer from the NFA-5 to NFA-4 as the NFA-4 exhibits a more significant dipole moment than the NFA-5 and is effectively dissociated into a free charge carrier.

Endgroup engineering of the third component for high-efficiency ternary organic solar cells

In this study, we carefully designed and synthesized three A-D-A type molecules, namely YF-C8-CN, YF-C8-S, and YF-C8-O. These molecules feature a 2,2′-bithiophene core, which bears two 2,4,6-tripropylbenzene steric hindrance groups, as the central electron-donating unit, and utilize rhodanine (Rh), thiazolidinedione, and dicyanoyl-modified benzotriazole (BTA) respectively as the electron acceptor unit (A-unit). We investigated their impact as the third component on the performance of ternary organic solar cells (OSCs). Our studies indicate that YF-C8-S, with rhodanine terminal groups, exhibits complementary absorption characteristics and cascaded energy levels when combined with the host binary system (D18:eC9-4F). Compared to YF-C8-CN and YF-C8-O, ternary OSCs based on YF-C8-S demonstrate significantly higher exciton diffusion and charge transport efficiency, favorably impacting the short-circuit current density (JSC) and fill factor (FF) of the OSCs. Furthermore, devices based on YF-C8-S exhibit reduced non-radiative energy loss, contributing to an enhanced open-circuit voltage (VOC). Consequently, ternary OSCs based on YF-C8-S achieve a remarkable efficiency of 19.12%, positioning it among the highest reported values. This comprehensive research on the third component of the YF-C8 series underscores their significant potential for fabricating high-performance ternary OSCs.

A Perspective on 2D Fused-Ring Quad-Rotor-Shaped Nonfullerene Acceptors with an Anthracene Core.

Previous studies have demonstrated the remarkable properties of quad-rotor-shaped two-dimensional nonfullerene acceptors (2D NFAs), which encompass exceptional electron affinity, robust sunlight absorption, effective exciton separation, and accelerated electron transfer capabilities. Naphthalene has been demonstrated to be a significant 2D fused core to construct high-performance 2D NFAs. However, synthesizing such materials through existing synthetic pathways poses a significant challenge. In this work, we designed four 2D NFAs (TEA-SIC, TEA-SIC-8F, TEA-SIC-OH, and TEA-SIC-OH-8F) with an anthracene core. These NFAs can theoretically be synthesized into a quad-rotor configuration through a seven-step synthetic process. Theoretical calculations have demonstrated that these 2D NFAs exhibit superior electron-accepting abilities, enhanced sunlight absorption, and more efficient exciton dissociation compared to Y6. Furthermore, TEA-SIC and TEA-SIC-8F exhibited impressive electron mobilities of 1.76 × 10-3 cm2 V-1 s-1 and 1.18 × 10-3 cm2 V-1 s-1, respectively, indicating their suitability for the development of high-performance organic solar cells (OSCs). Although TEA-SIC-OH and TEA-SIC-OH-8F have lower electron mobility, their high sunlight absorption and efficient exciton separation suggest potential as third components in ternary OSCs. These 2D NFAs also exhibit a commendable solubility in most alcohol-based solvents, indicating their potential for specialized applications in the fabrication of stacked OSCs. These findings provide valuable insights for the future design of synthesizable high-performance 2D NFAs.

Realization of Evaporated Electrode-Based Intrinsically Stretchable Ternary Organic Solar Cells through Encapsulation Strategy

Realization of Evaporated Electrode-Based Intrinsically Stretchable Ternary Organic Solar Cells through Encapsulation Strategy

Regulating Molecular Structure of S,N‐Heteroacene Non‐fullerene Acceptors to Achieve Efficient Photoelectric Properties†

Comprehensive SummaryThe ternary strategy has demonstrated its efficacy in improving charge transport in organic solar cells (OSCs). Here, three novel non‐fullerene acceptors, SN6C9‐4F, SN6C9‐4Cl and SN6C10‐4F, based on S,N‐heteroacene linear backbone were designed and synthesized. The three acceptors exhibit excellent molecular coplanarity, high crystallinity and possess a deep‐lying lowest unoccupied molecular orbital energy level, which is beneficial for charge transport and injection in organic field‐effect transistors (OFETs). Notably, the OFET devices based on all three acceptors achieved impressive electron mobilities, with SN6C10‐4F achieving up to 0.73 cm2·V–1·s–1, which is one of the highest values among A‐D‐A type small molecules. In addition, the OSCs device based on PBDB‐T:SN6C9‐4F exhibited the best power conversion efficiency of 12.07% owing to its optimal morphology and enhanced charge transport. Moreover, the incorporation of SN6C9‐4F into the efficient PM6:L8‐BO binary system to form ternary OSCs resulted in extended absorption range, enhanced donor crystallization, improved and more balanced charge transport, ultimately leading to an improvement of PCE from 17.78% to 18.32%. This study highlights the potential of developing acceptors with distinct structures from Y‐series acceptors to broaden absorption and regulate donor crystallization, providing a novel approach to enhance the PCE of OSCs.

Over 19 % efficienct ternary organic solar cells enabled by tuning charge behaviors through quinoxalineimide-based Y-type acceptors

Attaining a balanced charge carrier generation is a significant challenge in organic photovoltaics (OPVs). To enhance device performance, the ternary strategy has emerged as an effective approach. In this study, two Y6 derivatives, QIP-4F and QIP-4Cl, containing quinoxalineimide (QI) building blocks fused with thienylthiophene as the central unit were incorporated into the PM6:L8-BO system. The quinoxalineimide units reduce the energy losses in charge carrier extraction and non-radiative charge recombination. Furthermore, the increasing steric hindrance in the central block impacts phase separation and ordered intermolecular packing, which enhances the charge transport and minimizes the charge recombination. Ultimately, the PM6:L8-BO:QIP-4Cl device achieved a champion efficiency of 19.05%, offering a promising direction for enhancing the photovoltaic performance of OPVs.

Dipole Moment Modulation of Terminal Groups Enables Asymmetric Acceptors Featuring Medium Bandgap for Efficient and Stable Ternary Organic Solar Cells.

This study puts forth a novelterminal groupdesign todevelopmedium-bandgap Y-series acceptors beyond conventional side-chain engineering.We focused onthe strategical integration of an electron-donating methoxy group and an electron-withdrawing halogen atomatbenzene-fusedterminal groups. This combination preciselymodulatedthedipole moment and electron density of terminal groups, effectively attenuating intramolecular charge transfereffect, and widening the bandgap ofacceptors. The incorporation of theseterminalgroups yielded two asymmetric acceptors, named BTP-2FClO and BTP-2FBrO, both of which exhibited open-circuit voltage (VOC) as high as 0.96 V in binary devices, representing thehighestVOCs among the asymmetric Y-seriessmall molecule acceptors. More importantly, both BTP-2FClO and BTP-2FBrO exhibitmodestaggregation behaviorsandmolecular crystallinity,making themsuitable as a third component to mitigate excess aggregation of the PM6: BTP-eC9 blend and optimize thedevices'morphology.As a result,the optimized BTP-2FClO-based ternary organic solar cells (OSCs) achieved a remarkable power conversionefficiency (PCE)of 19.34%, positioning it among the highest-performing OSCs.Ourstudyhighlights themolecular designimportance on manipulating dipole moments and electron densityindevelopingmedium-bandgap acceptors,andoffersa highly efficient third component forhigh-performance ternary OSCs.

Machine learning empowers efficient design of ternary organic solar cells with PM6 donor

Organic solar cells (OSCs) hold great potential as a photovoltaic technology for practical applications. However, the traditional experimental trial-and-error method for designing and engineering OSCs can be complex, expensive, and time-consuming. Machine learning (ML) techniques enable the proficient extraction of information from datasets, allowing the development of realistic models that are capable of predicting the efficacy of materials with commendable accuracy. The PM6 donor has great potential for high-performance OSCs. However, it is crucial for the rational design of a ternary blend to accurately forecast the power conversion efficiency (PCE) of ternary OSCs (TOSCs) based on a PM6 donor. Accordingly, we collected the device parameters of PM6-based TOSCs and evaluated the feature importance of their molecule descriptors to develop predictive models. In this study, we used five different ML algorithms for analysis and prediction. For the analysis, the classification and regression tree provided different rules, heuristics, and patterns from the heterogeneous dataset. The random forest algorithm outperforms other prediction ML algorithms in predicting the output performance of PM6-based TOSCs. Finally, we validated the ML outcomes by fabricating PM6-based TOSCs. Our study presents a rapid strategy for assessing a high PCE while elucidating the substantial influence of diverse descriptors.

Configurational Isomerization-Induced Orientation Switching: Non-Fused Ring Dipodal Phosphonic Acids as Hole-Extraction Layers for Efficient Organic Solar Cells.

Phosphonic acid (PA) self-assembled molecules have recently emerged as efficient hole-extraction layers (HELs) for organic solar cells (OSCs). However, the structural effects of PAs on their self-assembly behaviors on indium tin oxide (ITO) and thus photovoltaic performance remain obscure. Herein, we present a novel class of PAs, namely "non-fused ring dipodal phosphonic acids" (NFR-DPAs), featuring simple and malleable non-fused ring backbones and dipodal phosphonic acid anchoring groups. The efficacy of configurational isomerism in modulating the photoelectronic properties and switching molecular orientation of PAs atop electrodes results in distinct substrate surface energy and electronic characteristics. The NFR-DPA with linear (C2h symmetry) and brominated backbone exhibits favorable face-on orientation and enhanced work function modification capability compared to its angular (C2v symmetry) and non-brominated counterparts. This makes it versatile HELs in mitigating interfacial resistance for energy barrier-free hole collection, and affording optimal active layer morphology, which results in an impressive efficiency of 19.11% with a low voltage loss of 0.52 V for binary OSC devices and an excellent efficiency of 19.66% for ternary OSC devices. This study presents a new dimension to design PA-based HELs for high-performance OSCs.

Highly efficient and stable binary and ternary organic solar cells using polymerized nonfused ring electron acceptors.

This study reports the successful design and synthesis of two novel polymerized nonfused ring electron acceptors, P-2BTh and P-2BTh-F, derived from the high-performance nonfused ring electron acceptor, 2BTh-2F. Prepared via Stille polymerization, these polymers feature thiophene and fluorinated thiophene as π-bridge units. Notably, P-2BTh-F, with difluorothiophene as the π-bridge, exhibits a more planar backbone and red-shifted absorption spectrum compared with P-2BTh. When employed in organic solar cells (OSCs) with PBDB-T as the donor material, P-2BTh-F-based devices demonstrate an outstanding power conversion efficiency (PCE) of over 11%, exceeding the 8.7% achieved by P-2BTh-based devices. Furthermore, all-polymer solar cells utilizing PBDB-T:P-2BTh-F exhibit superior storage stability. Additionally, P-2BTh-F was explored as a functional additive in a high-performance binary system, enhancing stability while maintaining comparable PCE (19.45%). This strategy offers a cost-effective approach for fabricating highly efficient and stable binary and ternary organic solar cells, opening new horizons for cost-effective and durable solar cell development.

All‐Small‐Molecule Ternary Organic Solar Cell with 16.35% Efficiency Enabled by Chlorinated Terminal Units

In the last few years, there have been notable developments in organic solar cells using both small molecule donor and acceptor. It has been noted that adding halogens to the end groups of small molecules could enhance the film structure and, consequently, the performance of the devices. In this study, three novel small molecule donors are created. The molecules include a vinyl‐CPDT oligomer with three units, with end‐caps made up of indanedione groups and containing four H, four Cl, and four F substituents. The purpose of the study is to investigate how the halogen substituent affects the photovoltaic characteristics of binary devices made with the non‐fullerene acceptor (NFA) TOCR2 as the acceptor. Having the halogen in the device enhances its effectiveness, and FG5, which has 4‐Cl substituents in the end groups, shows the highest efficiency among all devices with a PCE of 14.39%. Incredibly, the ternary device that is created in normal atmospheric conditions with chloro‐substituted FG5 as the donor, TOCR2 as the acceptor, and the wide band gap NFA DICTF as the third element shows significantly improved efficiency, achieving PCE values of up to 16.35%.

Optimization of the Active Layer Thickness for Inverted Ternary Organic Solar Cells Achieves 20% Efficiency with Simulation

Optimization of the Active Layer Thickness for Inverted Ternary Organic Solar Cells Achieves 20% Efficiency with Simulation

Exploiting Mechanism of Enhanced Charge Transfer in Ternary Organic Solar Cells at Low Energy Loss

The structural disorder and aggregation of the third acceptor with the host active layer are critical in the light absorption, film morphology, and charge‐carrier mechanism of their photovoltaic blends to achieve highly efficient organic solar cells (OSCs). However, an effective third component needs to be introduced in the host binary blend as a combination of ternary blend, which can improve the absorption profile, film morphology, and charge dynamics. In this work, non‐fullerene acceptor DRCTF is incorporated as a third component in host PM6:Y6 binary blend. Compared to host blend, the ternary blend improves charge‐transfer processes, as evidenced by steady‐state photoluminescence and time‐resolved photoluminescence measurements. It is found that the addition of 20% DRCTF into host binary blend results in improved charge dissociation and transport with reduced recombination, and voltage losses. All these characteristics contribute to an improved power conversion efficiency of 14.45% in the PM6:Y6:DRCTF ternary OSCs (T‐OSCs), compared to PM6:Y6 (12.46%) in open‐air fabrication conditions. Consequently, in this study, the impact of third components on the charge‐transfer mechanism in T‐OSCs is elucidated. These findings suggested that T‐OSCs with a perfectly chosen third component in the host binary blend achieve a comprehensive absorption profile, smooth film morphology, efficient charge dynamics, and reduced voltage loss.

Dimerized small molecule donor enables efficient ternary organic solar cells

Ternary organic solar cells (OSCs) are the feasible and efficient strategy to achieve the high-performance OSCs. It is of great significance to develop a superior third component candidate for constructing efficient ternary OSCs. In this work, we intelligently designed and synthesized a dimerized small molecule donor by connecting two asymmetric small molecule donors with the vinyl group, which is named DSMD-βV. This innovative oligomeric molecule DSMD-βV not only exhibits the complementary absorption and the cascade energy level arrangement with PM6 and BTP-eC9, but also regulates the phase separation micromorphology based on PM6:BTP-eC9. Consequently, PM6:DSMD-βV:BTP-eC9 based ternary device exhibits the improved exciton dissociation, charge transport and decreased recombination, thus achieving a superior power conversion efficiency (PCE) of 18.26 %, surpassing PM6:BTP-eC9 based binary (17.63 %). This work indicates that the dimerized small molecule donor is able to become a promising third component candidate, which also opens up a unique idea for the construction of efficient ternary organic solar cells.

Enhanced Fill Factor and Efficiency of Ternary Organic Solar Cells by a New Asymmetric Non-Fullerene Small Molecule Acceptor.

Asymmetric non-fullerene small molecules acceptor (as-NF-SMAs) exhibit greater vitality in photovoltaic materials compared to their symmetric counterparts due to their larger dipole moments and stronger intermolecular interactions, which facilitate exciton dissociation and charge transmission in organic solar cells (OSCs). Here, we introduced a new as-NF-SMAs, named IDT-TNIC, as the third component in ternary organic solar cells (TOSCs). The asymmetric IDT-TNIC used indacenodithiophene (IDT) as the central core, alkylthio-thiophene as a unilateral π-bridge and extended end groups as electron-withdrawing. Due to the non-covalent conformational lock (NCL) established between O⋅⋅⋅S and S⋅⋅⋅S, the IDT-TNIC molecule preserves its coplanar structure effectively. Furthermore, IDT-TNIC exhibits complementary absorption and excellent compatibility with donor and acceptor materials, as well as optimized ladder energy level arrangement, resulting in a higher and more balanced μh/μe value, more homogeneous and suitable phase separation morphology in TOSCs. Thus, the PCE of the TOSCs reached 17 % when the weight ratio of PM6 : Y6 : IDT-TNIC was 1 : 1.1 : 0.1, and it is noteworthy that when the device area was increased to 1 cm2, the PCE could still be maintained at over 14 %. Detailed studies and analysis indicate that IDT-TNIC has great potential as a third component in OSCs and for large-scale printing in the future.

Designing A–D–A Type Fused‐Ring Electron Acceptors with a Bulky 3D Substituent at the Central Donor Core to Minimize Non‐Radiative Losses and Enhance Organic Solar Cell Efficiency

AbstractDesigning and synthesizing narrow band gap acceptors that exhibit high photoluminescence quantum yield (PLQY) and strong crystallinity is a highly effective, yet challenging, approach to reducing non‐radiative energy losses (▵Enr) and boosting the performance of organic solar cells (OSCs). We have successfully designed and synthesized an A–D–A type fused‐ring electron acceptor, named DM‐F, which features a planar molecular backbone adorned with bulky three‐dimensional camphane side groups at its central core. These bulky substituents effectively hinder the formation of H‐aggregates of the acceptors, promoting the formation of more J‐aggregates and notably elevating the PLQY of the acceptor in the film. As anticipated, DM‐F showcases pronounced near‐infrared absorption coupled with impressive crystallinity. Organic solar cells (OSCs) leveraging DM‐F exhibit a high EQEEL value and remarkably low ▵Enr of 0.14 eV‐currently the most minimal reported value for OSCs. Moreover, the power conversion efficiency (PCE) of binary and ternary OSCs utilizing DM‐F has reached 16.16 % and 20.09 %, respectively, marking a new apex in reported efficiency within the OSCs field. In conclusion, our study reveals that designing narrow band gap acceptors with high PLQY is an effective way to reduce ▵Enr and improve the PCE of OSCs.