Non-halogenated Solvents Research Articles

18.63% Efficiency of Ternary Organic Solar Cells Achieved via Nonhalogenated Solvent and Hot Spin‐Coating Process

AbstractThe solubility problem of conjugated polymers in nonhalogenated solvents limits the application of nonhalogenated solvents in Organic solar cells (OSCs). By combining with a hot spin‐coating process, efficient PM6:BTP‐BO‐4F:GS‐ISO ternary OSCs are prepared by employing o‐xylene as a solvent. After adding 10 wt% content of GS‐ISO to PM6:BTP‐BO‐4F, the surface morphology in the active layers is improved and the charge extraction, transport, and collection in OSCs are enhanced. Compared with the efficiency of PM6:BTP‐BO‐4F OSCs (16.25%), an efficiency of 18.63% is achieved for PM6:BTP‐BO‐4F:GS‐ISO ternary OSCs. Moreover, PM6:BTP‐BO‐4F:GS‐ISO ternary OSCs with an efficiency of 14.13% are prepared in air. The work provides a new strategy for preparing efficient and environmentally friendly OSCs using green solvents.

Polymer donors with hydrophilic side-chains enabling efficient and thermally-stable polymer solar cells by non-halogenated solvent processing

Polymer donors with hydrophilic side-chains enabling efficient and thermally-stable polymer solar cells by non-halogenated solvent processing

Efficient organic solar cells enabled by sustainable and synergetic device engineering

In order to accelerate the transfer of organic solar cells (OSCs) from lab to fab, this work develops a synergetic strategy by integrating low-cost material, green solvent, bio-based additive and low-temperature post-treatment to sustainably fabricate OSCs. The donor polymer PTQ10 composing of simple building blocks, accompanied by the acceptor L8-BO, is dissolved in the green solvent tetrahydrofuran, wherein a bio-based cinnamonitrile is firstly used as solvent additive. Moreover, fluorous solvent soaking (FSS) is employed as post-treatment to replace the high-temperature and time-consuming thermal annealing. Systematic investigations are performed to unravel the mechanism of the device engineering developed in this work. Differing from the one-way movement of additive, the fluorous solvent can penetrate into and come out the film in cycles. Meanwhile, some L8-BO is selectively dissolved and brought out by the fluorous solvent, so this partial L8-BO bears the function as solid additive to optimize the morphology. As a result, the device achieves a remarkable power conversion efficiency of 17.11%, among the best efficiencies of OSCs prepared by non-halogenated non-aromatic solvents. In addition, the excellent universality ensures this strategy is also effective in the thick-film OSCs.

Eco-friendly volatile additive enabling efficient large-area organic photovoltaic module processed with non-halogenated solvent

Menthol (MT) can effectively promote ordered molecular arrangement of acceptors in non-halogenated solvent, contributing to the large-area organic photovoltaic modules (19.31 cm2) with a notable power conversion efficiency (PCE) of 15.74%.

Regulating pre-aggregation in non-halogenated solvent to enhance the efficiency of organic solar cells

Optimizing the morphology of an active layer in organic solar cells (OSCs) through precise control of precursor solution aggregation is a crucial step in enhancing photovoltaic performance. However, the considerable difference in solubility among organic materials in environmentally friendly solvents, such as non-halogenated solvents, poses a challenge in simultaneously modulating the pre-aggregation of both donor and acceptor. Herein, we employ a synergistic approach that involves heat treatment and the addition of a solid additive to regulate the aggregation behavior of PM6 (donor) and BTP-ec9 (acceptor) within an o-xylene solvent. Our findings reveal that PM6 exhibits strong temperature-dependent aggregation tendencies, while the solid additive 1,4-diiodobenzene (DIB) notably influences the aggregation of BTP-ec9. Thus, treating the precursor solution at 90 °C and adding DIB result in a well-matched aggregation between donor and acceptor, effectively optimizing the crystallization and phase separation morphology of the active layer. This strategic intervention leads to an outstanding efficiency of 18.07%, with a fill factor of 78.65%, for the corresponding device, which ranks among the highest efficiencies for the non-halogenated solvent-processed OSCs. Importantly, this study also demonstrates the feasibility of fabricating thick-film and large-area OSCs by blade-coating, achieving efficiencies of 16.15% and 15.29%, showcasing substantial potential for commercial applications.

Dithienoquinoxaline-quaterthiophene wide bandgap donor polymers with strong interchain aggregation for efficient organic solar cells processed with a non-halogenated solvent

Wide bandgap oligothiophene based polymers PQx4T and PQx4T-2F were synthesized, among which PQx4T-2F was very efficient to construct toluene-processed active layers with a non-fullerene acceptor.

C-shaped ortho-benzodipyrrole-based acceptors with different electronic effects of top substituents for as-cast green-solvent processed high-performance organic solar cells

We systematically investigated the effects of the top substituents on the physicochemical properties of SMAs and achieved the highest PCE for OSCs processed using a non-halogenated solvent without any extra treatment.

Improving voltage and quantum efficiency in blade-coated ITO-free organic solar cells processed with a non-halogenated solvent

ITO-free OSCs (PM6:Y6) blade-coated with o-xylene show enhanced donor–acceptor separation and trap density, leading to limited VOC. Acceptor side chain modification enhances the morphology and reduces traps, boosting photovoltaic performance.

A sustainable protocol for the synthesis of N-acyl tryptamines, a class of potential gut microbiota-derived endocannabinoid-like mediators.

A simple and sustainable propylphosphonic anhydride (T3P)-assisted methodology for the synthesis of N-acyl tryptamines, an interesting class of gut microbiota-derived endocannabinoid-like lipid mediators, was proposed. This protocol is characterized by great operational simplicity, and all products were obtained at room temperature, without the use of an inert atmosphere and by using limited amounts of non-halogenated solvents. Finally, the possibility to realize the reaction under mechanochemical conditions was explored with interesting results.

Eco-friendly solution-processed narrowband OLEDs using non-halogenated aliphatic solvent systems

In general, fabricating multilayer structures in solution-processed organic light-emitting diodes (OLEDs) presents challenges owing to the potential degradation of the initial film during subsequent processing steps. Furthermore, these devices typically require aromatic and halogenated solvents recognized for their adverse effects on human health and their harmful environmental impact. In this study, we successfully synthesized a solution-processable multi-resonance thermally activated delayed fluorescence (MR-TADF) emitter by introducing tert-butyl carbazolyl dendron, which exhibits excellent solubility. In our approach, we fabricated a multilayer OLED for solution processing utilizing eco-friendly, non-halogenated aliphatic solvents, with each layer in the devices developed utilizing water, cyclohexanone, and ethyl acetate for the hole injection layer, hole transport layer, and emitting layer, respectively. The resulting eco-friendly solution-processed OLED achieved a maximum external quantum efficiency (EQEmax) of 14.0 % and a narrow bandwidth of 30 nm. Furthermore, utilizing an additional TADF sensitizer led to a remarkable EQEmax enhancement of over 15 % and a substantial improvement in efficiency roll-off. Thus, the eco-friendly device fabrication strategy employed here opens novel avenues for diverse research in organic semiconductor devices that must be fabricated with solution processes in the future.

In Situ Self‐Assembly of Trichlorobenzoic Acid Enabling Organic Photovoltaics with Approaching 19% Efficiency

AbstractFuture industrialization of organic photovoltaics (OPVs) requires OPVs’ processing to be more energy‐efficient and streamlined. Currently, only MoO3 and PEDOT:PSS are commonly used as the anode interface layer (AIL). The processing of MoO3 typically involves vacuum thermal evaporation with stringent thickness requirements. PEDOT:PSS necessitates separate processing and thermal annealing at temperatures exceeding 100 °C to eliminate moisture. This work utilized 3,4,5‐trichlorobenzoic acid (3CBA) as the AIL material. The distinct advantage of 3CBA over PEDOT:PSS and MoO3 is the in situ self‐assembly of 3CBA eliminates the need for separate solution processing, thermal evaporation, or thermal annealing. Remarkably, OPV devices incorporating PM6, BTP‐eC9, and the 3CBA AIL exhibited a superior efficiency of 18.2% compared to those with PEDOT:PSS (17.7%). By using nonhalogenated solvent, o‐xylene, to meet industrialization requirements, the devices achieved an exceptional efficiency of 18.8%, the highest reported value among devices with in situ self‐assembled interface layers. Furthermore, semi‐transparent devices with 3CBA displayed higher PCE and AVT values (13.1% and 25.7%) than their PEDOT: PSS counterparts, due to the weak absorption of the 3CBA AIL. This work contributes significantly to the high‐throughput production of OPVs by streamlining the AIL processing.

Hot-Casting Strategy Empowers High-Boiling Solvent-Processed Organic Solar Cells with Over 18.5% Efficiency.

Most top-rank organic solar cells (OSCs) are manufactured by the halogenated solvent chloroform, which possesses a narrow processing window due to its low-boiling point. Herein, based on two high-boiling solvents, halogenated solvent chlorobenzene (CB) and non-halogenated green solvent ortho-xylene (OX), preparing active layers with the hot solution is put forward to enhance the performance of the OSCs. In situ test and morphological characterization clarify that the hot-casting strategy assists in the fast and synchronous molecular assembly of both donor and acceptor in the active layer, contributing to preferable donor/acceptor ratio, vertical phase separation, and molecular stacking, which is beneficial to charge generation and extraction. Based on the PM6:BO-4Cl, the hot-casting OSCs with a wide processing window achieve efficiencies of 18.03% in CB and 18.12% in OX, which are much higher than the devices processed with room temperature solution. Moreover, the hot-casting devices with PM6:BTP-eC9 deliver a remarkable fill factorof 80.31% and efficiencyof 18.52% in OX, representing the record value among binary devices with green solvent. This work demonstrates a facile strategy to manipulate the molecular distribution and arrangement for boosting the efficiency of OSCs with high-boiling solvents.

Introducing a Phenyl End Group in the Inner Side Chains of A-DA'D-A Acceptors Enables High-Efficiency Organic Solar Cells Processed with Nonhalogenated Solvent.

Power conversion efficiency (PCE) of organic solar cells (OSCs) processed by nonhalogenated solvents is unsatisfactory due to the unfavorable morphology. Herein, two new small molecule acceptors(SMAs) Y6-Ph and L8-Ph are synthesized by introducing a phenyl end group in the inner side chains of the SMAs of Y6 and L8-BO, respectively, for overcoming the excessive aggregation of SMAs in the long-time film forming processed by nonhalogenated solvents. First, the effect of the film forming time on the aggregation property and photovoltaic performance of Y6, L8-BO, Y6-Ph, and L8-Ph is studied by using the commonly used solvents: chloroform (CF) (rapid film forming process) and chlorobenzene (CB) (slow film forming process). It isfound that Y6- and L8-BO-based OSCs exhibit a dramatic drop in PCEfrom CF- to CB-processed devices owing to the large phase separation, while the Y6-Ph and L8-Ph based OSCs show obviously increased PCEs Furthermore, L8-Ph-based OSCs processed by nonhalogenated solvent o-xylene (o-XY) achieved a high PCE of 18.40% with an FF of 80.11%. The results indicate that introducing a phenyl end group in the inner side chains is an effective strategy to modulate the morphology and improve the photovoltaic performance of the OSCs processed by nonhalogenated solvents.

Achieving an excellent efficiency of 11.57% in a polymer solar cell submodule with a 55 cm2 active area using 1D/2A terpolymers and environmentally friendly nonhalogenated solvents

AbstractThe transition of polymer solar cells (PSCs) from laboratory‐scale unit cells to industrial‐scale modules requires the development of new p‐type polymers for high‐performance large‐area PSC modules based on environmentally friendly processes. Herein, a series of 1D/2A terpolymers (PBTPttBD) composed of benzo[1,2‐b:4,5‐b’]dithiophene (BDT‐F), thieno[3,4‐c]pyrrole‐4,6(5H)‐dione (TPD‐TT), and benzo‐[1,2‐c:4,5‐c’]dithiophene‐4,8‐dione (BDD) is synthesized for nonhalogenated solvent processed PSC submodules. The optical, electrochemical, charge‐transport, and nano‐morphological properties of the PBTPttBD terpolymers are modulated by adjusting the molar ratio of the TPD‐TT and BDD components. PBTPttBD‐75:BTP‐eC11‐based PSC submodules, processed with o‐xylene, achieve a notable PCE of 11.57% over a 55 cm2 active area. This PCE value is among the highest reported using a nonhalogenated solvent over a 55 cm2 active area module. The optimized PSC submodule exhibits minimal cell‐to‐module loss, which can be attributed to the optimized crystallinity of the PBTPttBD‐75:BTP‐eC11 photoactive layer system and favorable film formation kinetics.image

Ultra-Stable ITO-Free Organic Solar Cells and Modules Processed from Non-Halogenated Solvents under Indoor Illumination.

Organic Photovoltaics (OPV) is a very promising technology to harvest artificial illumination and power smart devices of the Internet of Things (IoT). Efficiencies as high as 30.2% have been reported for OPVs under warm white light-emitting diode (LED) light. This is due to the narrow spectrum of indoor light, which leads to an optimal bandgap of ≈1.9eV. Under full sunlight, OPV devices often suffer from poor stability compared to the established inorganic PV technologies such as crystalline silicon. This study focuses on a potentially very cost-effective Indium Tin Oxide (ITO) free cell stack with absorber materials processed from non-halogenated solvents. These organic solar cells and modules with efficiencies up to 21% can already achieve remarkable stabilities under typical indoor illumination. Aging under 50,000lux LED lighting leads to very little degradation after more than 11000h. This light dose corresponds to more than 110years under 500lux. For modules encapsulated with a flexible barrier, extrapolated lifetimes of more than 41years are achieved. This shows that OPV is mature for the specific application under indoor illumination. Due to the large number of potential organic semiconducting materials, further efficiency increase can be expected.

Correlation of Broad Absorption Band with Small Singlet-Triplet Energy Gap in Organic Photovoltaics.

Organic photovoltaics (OPV) are one of the most effective ways to harvest renewable solar energy, with the power conversion efficiency (PCE) of the devices soaring above 19% when processed with halogenated solvents. The superior photocurrent of OPV over other emerging photovoltaics offers more opportunities to further improve the efficiency. Tailoring the absorption band of photoactive materials is an effective way to further enhance OPV photocurrent. However, the field has mostly been focusing on improving the near-infrared region photo-response, with the absorption shoulders in short-wavelength region (SWR) usually being neglected. Herein, by developing a series of non-fullerene acceptors (NFAs) with varied side-group conjugations, we observe an enhanced SWR absorption band with increased side-group conjugation length. The underpinning factors of how molecular structures and geometries improve SWR absorption are clearly elucidated through theoretical modelling and crystallography. Moreover, a clear relationship between SWR absorption intensity and singlet-triplet energy gap is established. These collectively establish a comprehensive correlation from NFA structure to non-radiative recombination loss in OPV, affording a high PCE of 18.5% when processed with a non-halogenated green solvent.

A-A Strategy Enables Desirable Performance of All-Polymer Solar Cells Fabricated with Nonhalogenated Solvents.

Most polymer acceptors have been designed by applying a D (electron-rich unit)-A (electron-deficient unit) strategy, which are principally processed with halogenated solvents to fabricate all-polymer solar cells (all-PSCs). Two novel polymer acceptors, containing an A-A type backbone, were designed and synthesized, which can be readily dissolved in o-xylene. The polymer PY-FBTA, comprising a Y6 derivative as the first A unit and a benzotriazole derivative as the second A unit, shows smaller dihedral angles in the backbone, stronger molecular interactions, higher LUMO level, more complementary absorption spectrum, and better morphology with PM6 than the polymer PY-DPP comprising a diketopyrrolopyrrole derivative as the second A unit. Accordingly, the PM6:PY-FBTA all-PSC achieves a higher PCE of 13.95% than the all-PSC based on PM6:PY-DPP (9.51%) for thoroughly improved Jsc (22.34 mA cm-2), Voc (0.963 V), and FF (64.84%) values, which are fabricated with o-xylene as the solvent. This work demonstrates that the A-A structure is a desirable strategy for designing polymer acceptors for efficient all-PSCs prepared with nonhalogenated solvents.

Spontaneous vertical phase distribution of multi-acceptors system enables high-efficiency organic photovoltaics in non-halogenated solvent and large-area module application

Building a vertical phase distribution morphology with a simple method is the critical key for high-efficiency organic photovoltaics (OPVs) and their industrial application. Here, OPVs based on a quaternary system with one donor PM6 and three acceptors (L8-BO, BTP-S8, and BTP-S2) were fabricated. The L8-BO-based blend was demonstrated to show unique vertical phase distribution (acceptors enriched on the top surface), leading to an exquisite morphology and superior carrier behaviors, thus power conversion efficiencies (PCEs) of 19.19% (certified as 19.18%) and 19.04% were achieved for chloroform-processed and toluene-processed devices, respectively. The high efficiency obtained from greener solvent is encouraging for commercialization of OPVs. Notably, the device processed with toluene without any additives shows a PCE of 17.28% with good stability, and the upscaled large-area module with a total area of 72.25 cm2 processed in air presents an outstanding PCE of 12.78%. This work provides valuable insights into the fabrication of greener solvent and large-area module OPVs.

Green-Processed Non-Fullerene Organic Solar Cells Based on Y-Series Acceptors.

The development of environmentally friendly and sustainable processes for the production of high-performance organic solar cells (OSCs) has become a critical research area. Currently, Y-series electron acceptors are widely used in high-performance OSCs, achieving power conversion efficiencies above 19%. However, these acceptors have large fused conjugated backbones that are well-soluble in halogenated solvents, such as chloroform and chlorobenzene, but have poor solubility in non-halogenated green solvents. To overcome this challenge, recent studies have focused on developing green-processed OSCs that use non-chlorinated and non-aromatic solvents to dissolve bulk-heterojunction photoactive layers based on Y-series electron acceptors, enabling environmentally friendly fabrication. In this comprehensive review, an overview of recent progress in green-processed OSCs based on Y-series acceptors is provided, covering the determination of Hansen solubility parameters, the use of non-chlorinated solvents, and the dispersion of conjugated nanoparticles in water/alcohol. It is hoped that the timely review will inspire researchers to develop new ideas and approaches in this important field, ultimately leading to the practical application of OSCs.

Slot-die coated large-area flexible all-polymer solar cells by non-halogenated solvent

Slot-die coated large-area flexible all-polymer solar cells by non-halogenated solvent