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Charge carrier nonradiative recombination (NRR) caused by interface defects and nonoptimal energy level alignment is the primary factor restricting the performance improvement of perovskite solar cells (PSCs). Interfacial modification is a vital strategy to restrain NRR and enable high-performance PSCs. We report here two interfacial materials, PhI-TPA and BTZI-TPA, consisting of phthalimide and a 2,1,3-benzothiadiazole-5,6-dicarboxylicimide core, respectively. The difunctionalized BTZI-TPA with imide and thiadiazole shows higher hole mobility, better aligned energy levels, and stronger interaction with uncoordinated Pb

Cyano substitution is vital to the molecular design of polymer semiconductors toward highly efficient organic solar cells. However, how regioselectivity impacts relevant optoelectronic properties in cyano-substituted bithiophene systems remain poorly understood. Three regioisomeric cyano-functionalized dialkoxybithiophenes BTHH, BTHT, and BTTT with head-to-head, head-to-tail, and tail-to-tail linkage, respectively, were synthesized and characterized in this work. The resulting polymer semiconductors (PBDTBTs) based on these building blocks were prepared accordingly. The regiochemistry and property relationships of PBDTBTs were investigated in detail. The BTHH moiety has a higher torsional barrier than the analogs BTHT and BTTT, and the regiochemistry of dialkoxybithiophenes leads to fine modulation in the optoelectronic properties of these polymers, such as optical absorption, band gap, and energy levels of frontier molecular orbitals. Organic field-effect transistors based on PBDTBTHH had higher hole mobility (4.4 × 10−3 cm2/(V·s)) than those (ca. 10−4 cm2/(V·s)) of the other two polymer analogs. Significantly different short-circuit current densities and fill factors were obtained in polymer solar cells using PBDTBTs as the electron donors. Such difference was probed in greater detail by performing space-charge-limited current mobility, thin-film morphology, and transient photocurrent/photovoltage characterizations. The findings highlight that the BTHH unit is a promising building block for the construction of polymer donors for high-performance organic photovoltaic cells. Graphical abstract

The non-fully conjugated polymer as a new class of acceptor materials has shown some advantages over its small molecular counterpart when used in photoactive layers for all-polymer solar cells (all-PSCs), despite a low power conversion efficiency (PCE) caused by its narrow absorption spectra. Herein, a novel non-fully conjugated polymer acceptor PFY-2TS with a low bandgap of ~1.40 eV was developed, via polymerizing a large π-fused small molecule acceptor (SMA) building block (namely YBO) with a non-conjugated thioalkyl linkage. Compared with its precursor YBO, PFY-2TS retains a similar low bandgap but a higher LUMO level. Moreover, compared with the structural analog of YBO-based fully conjugated polymer acceptor PFY-DTC, PFY-2TS shows a similar absorption spectrum and electron mobility, but significantly different molecular crystallinity and aggregation properties, which results in optimal blend morphology with a polymer donor PBDB-T and physical processes of the device in all-PSCs. As a result, PFY-2TS-based all-PSCs achieved a PCE of 12.31% with a small energy loss of 0.56 eV enabled by the reduced non-radiative energy loss (0.24 eV), which is better than that of 11.08% for the PFY-DTC-based ones. Our work clearly demonstrated that non-fully conjugated polymers as a new class of acceptor materials are very promising for the development of high-performance all-PSCs. [Figure not available: see fulltext.].

Summary There is an urgent demand for all-polymer organic solar cells (AP-OSCs) to gain higher efficiency. Here, we successfully improve the performance to 16.09% by introducing a small amount of BN-T, a B←N-type polymer acceptor, into the PM6:PY-IT blend. It has been found that BN-T makes the active layer, based on the PM6:PY-IT:BN-T ternary blend, more crystalline but meanwhile slightly reduces the phase separation, leading to enhancement of both exciton harvesting and charge transport. From a thermodynamic viewpoint, BN-T prefers to reside between PM6 and PY-IT, and the fraction of this fine-tunes the morphology. Besides, a significantly reduced nonradiative energy loss occurs in the ternary blend, along with the coexistence of energy and charge transfer between the two acceptors. The progressive performance facilitated by these improved properties demonstrates that AP-OSCs can possibly comparably efficient with those based on small molecule acceptors, further enhancing the competitiveness of this device type.

The purpose of this study was to synthesize a magnetic material that could be easily separated by a magnetic field and combined the catalytic function of an acid/base ionic liquid with silicon for biodiesel preparation. A kind of magnetic catalyst-immobilized ionic liquid was synthesized by a three-step method. The synthesis conditions in each step were optimized by single-factor analysis. Under the optimum conditions, 206.83 mg of ionic liquid (>43.63%) was immobilized on SiO2 (per gram). Heating under reflux was applied to extract Schisandra chinensis seed oil with an average yield of 10.9%. According to the biodiesel yields, Fe3O4@SiO2@[C4mim]HSO4 was the most efficient catalyst in the methyl esterification reaction. Under the optimum reaction conditions, seed oil (10.0 g) was mixed with methanol (70 mL) under continuous mechanical stirring for 3 h, and the yield of biodiesel was 0.557 g/g (the catalyst efficiency was about 89.2%). Also, the thermal value was increased from 32.14 kJ/g (seed oil) to 38.28 kJ/g (biodiesel). The catalytic efficiency of Fe3O4@SiO2@[C4mim]HSO4 was 87.6% of the first being used after four reuse cycles, and 71.4% of the first being used after six reuse cycles in the methylation reaction. The yields and physical and chemical properties of biodiesel were determined.

Organic photovoltaics (OPVs) are one of the most promising technologies to power indoor electronic devices. However, the limited types and design strategies of medium band-gap acceptor materials hinder the development of indoor OPVs. Currently, the state-of-the-art non-fullerene acceptors (NFAs) are Y6 and its derivatives, which are based on an A–DA′D–A structure. In this paper, we report the modification of the Y6 structure by replacing Y6's D unit (thieno[3,2-b]thiophene) with benzothiophene, and synthesize two novel NFAs (LBT-DF and LBT-SCl) for indoor applications. The use of the benzothiophene unit reduces the intermolecular charge transfer effect, thus blue-shifting the absorption spectra and up-shifting the LUMO energy levels of the NFAs. As a result, LBT-SCl achieves a higher Voc and thus PCE (up to 25.1%) than Y6 (22.2%) under indoor conditions. Interestingly, these two NFAs exhibit a non-planar aromatic structure, which is rarely observed in the published NFAs, because a better coplanar molecular configuration is usually considered as the critical factor in realizing high PCE. Different from the above mentioned molecular design concept, we find that non-planar structure acceptors also have great potential in OPVs. Our work provides an effective OPV material design guideline for developing high-performance indoor OPVs and also opens a new direction for the design of NFAs.

Low-cost and eco-friendly hole-transport materials (HTMs) are exceedingly desirable for the practical application of perovskite solar cells (PVSCs). Here, a traditional bidentate ligand (1,10-phenanthroline), widely used as a chelating agent for bioorganic reagents and probes, is incorporated into an HTM to afford M1. Such a planar bidentate ligand at the central core of the HTM can facilitate π–π stacking and enable chelation to Pb2+ ion defects and thus achieve efficient passivation at the M1/perovskite interface, contributing to reduced recombination loss. When employed as an HTM in inverted PVSCs without dopants, bidentate-ligand-based M1 yields a high power conversion efficiency (PCE) of 20.14%, which is significantly higher than that (18.32%) of the M0 analogue that contains phenanthrene. More importantly, green solvent processing (ethyl acetate) of M1 achieves a PCE of 19.21%, which is among the highest values reported in PVSCs with a green-solvent-processable HTM. Besides, the facile one-step synthesis route reduces the cost to 45 $ gram−1 for M1, which is cheaper than the most reported HTMs for high-efficiency PVSCs without dopants. These findings demonstrate the potential of bidentate ligands in developing cost-effective and eco-friendly HTMs toward highly efficient PVSCs.

It is widely known that the miscibility between donor and acceptor is a crucial factor that affects the morphology and thus device performance of nonfullerene organic solar cells (OSCs). In this Letter, we show that incorporating a third component with lower miscibility and higher lowest unoccupied molecular orbital (LUMO) level into the state-of-the-art PM6:Y6 system can significantly enhance the performance of devices. The best results of the ternary devices are achieved by adding a small molecular acceptor named ITCPTC (similar to 5% w/w), which significantly improves the power conversion efficiency (PCE) of the host system from 16.44% to 17.42%. The higher LUMO of the third component increases the open-circuit voltage (V-oc), while the low miscibility enlarges the domains and leads to improved short-circuit current density (J(sc)) and fill factor (FF). The efficacy of this strategy is supported by using other nonfullerene third components including an asymmetric small molecule (N7IT) and a polymer acceptor (PF2-DTC), which play the same role as ITCPTC and boost the PCEs to 16.96% and 17.04%, respectively. Our approach can be potentially applied to a wide range of OSC material systems and should facilitate the development of the OSC field.

The open-circuit voltage (Voc) of all-polymer solar cells (all-PSCs) is typically lower than 0.9 V even for the most efficient ones. Large energy loss is the main reason for limiting Voc and efficiency of all-PSCs. Herein, through materials design using electron deficient building blocks based on bithiophene imides, the lowest unoccupied molecular orbital (LUMO) energy levels of polymer acceptors can be effectively tuned, which resulted in a reduced energy loss induced by charge generation and recombination loss due to the suppressed charge-transfer (CT) state absorption. Despite a negligible driving force, all-PSC based on the polymer donor and acceptor combination with well-aligned energy levels exhibited efficient charge transfer and achieved an external quantum efficiency over 10% while maintaining a large Voc of 1.02 V, leading to a 9.21% efficiency. Through various spectroscopy approaches, this work sheds light on the mechanism of energy loss in all-PSCs, which paves an avenue to achieving efficient all-PSCs with large Voc and drives the further development of all-PSCs.

Compared with p-type terpolymers, less effort has been devoted to n-type analogs. Herein, we synthesized a series of n-type terpolymers via incorporating three electron-deficient third components including thienopyrroledione (TPD), phthalimide, and benzothiadiazole into an imide-functionalized parent n-type copolymer to tune optoelectronic properties without sacrificing the n-type characteristics. Due to effects of the third components with different electron-accepting ability and solubility, the resulting three polymers feature distinct energy levels and crystallinity. In addition, heteroatoms (S, O, and N) attached on the third components trigger intramolecular noncovalent interactions, which can increase molecule planarity and have a significant effect on the packing structures of the polymer films. As a result, the best power conversion efficiency of 8.28% was achieved from all-polymer solar cells (all-PSCs) based on n-type terpolymer containing TPD. This is contributed by promoted electron mobility and face-on polymer packing, showing the pronounced advantages of the TPD used as a third component for thriving efficient n-type terpolymers. The generality is also successfully validated in a benchmark polymer donor/acceptor system by introducing TPD into the benchmark n-type polymer N2200. The results demonstrate the feasibility of introducing suitable electron-deficient building blocks as the third components for high-performance n-type terpolymers toward efficient all-PSCs.

Summary High-performance n-type (electron-transporting or n-channel) polymer semiconductors are critical components for the realization of various organic optoelectronic devices and complementary circuits, and recent progress has greatly advanced the performance of organic thin-film transistors, all-polymer solar cells, and organic thermoelectrics, to cite just a few. This Perspective focuses on the recent development of high-performance n-type polymer structures, particularly those based on the most investigated and novel electron-deficient building blocks, as well as summarizes the performance achieved in the above devices. In addition, this Perspective offers our insights into developing new electron-accepting building blocks and polymer design strategies, as well as discusses the challenges and opportunities in advancing n-type device performance.

Summary Generally, it is important to fine-tune the energy levels of donor and acceptor materials in the field of polymer solar cell (PSCs) to achieve a minimal highest occupied molecular orbital (HOMO) energy offset, which yet is still sufficient for charge separation. Based on the high-performance small-molecule acceptor (SMA) of BTP-4F, we modified the end groups of BTP-4F from IC-2F to CPTCN-Cl. It was found that when both end groups were substituted by CPTCN-Cl, the energy level upshift was too large that caused unfavorable energetic alignment, thus poor device performance. By using the strategy of asymmetric end groups, we were able to achieve near optimal energy level match, resulting in higher open-circuit voltage (VOC) and power conversion efficiency (PCE) compared with those given by the PM6:BTP-4F system. Our strategy can be useful and potentially applied to other material systems for maximizing efficiency of non-fullerene PSCs.

Developing scalable and robust processing methods with low material waste remains a challenge for organic solar cells (OSCs) to become a practical renewable energy source. Here, we present a novel low-cost processing approach termed as soft porous blade printing (SPBP), which uses a layer of soft porous material such as filter paper as the printing blade. The inherent porous microstructure of the blade offers high shear rates that facilitate the alignment, crystallization, and orientation of active materials during printing. Moreover, by eliminating the suspended liquid meniscus, SPBP relaxes the stringent requirement of gap control and enables continuous ink delivery for uninterrupted film fabrication with adjustable thickness. Higher photovoltaic performances are achieved in the SPBP-printed OSCs than those of the spin-coated counterparts for two nonfullerene-acceptor active-layer systems (Y6:PM6 and PTQ10:IDIC). Y6:PM6 cells printed by SPBP without any additive exhibit power conversion efficiencies up to 14.75%, which is among the highest reported to date for non-spin-coated OSCs.

All-polymer solar cells (all-PSCs), which utilize polymer donor (PD)/polymer acceptor (PA) blend films as the photoactive layer, have attracted considerable attention and achieved substantial progress. Nevertheless, only a few PAs have led to power conversion efficiencies (PCEs) >8% in all-PSCs, and most of them are naphthalene diimide-based polymers. Herein, a series of PAs named PBTI2(xDT)-FT have been developed, which consist of a 2,5-bis(2-thienyl)thieno[3,2-b]thiophene diimide (BTI2)-alt-3,4-difluorothiophene polymer backbone, where the ratios of 2-decyltetradecyl (DT) and 2-octyldodecyl (OD) side chains on BTI2 have been varied such that x designates the percentage of BTI2 units with DT side chains (i.e. 0, 30, 50, 70, and 100). The side chain engineering aims to fine-tune the polymer chain packing and thus optimize the film morphology. When applied in all-PSCs through additive-free processing, the PBTI2(50DT)-FT-based cells yield a promising PCE of 8.32% with the well-known PTB7-Th as the polymer donor, substantially higher than those of the two parent copolymers (6.82% for PBTI2(0DT)-FT and 4.30% for PBTI2(100DT)-FT). This PCE is also one of the highest for additive-free all-PSCs. Moreover, the devices show a good stability with 90% of the initial PCE retained after 400 h. This work demonstrates the effectiveness of side chain engineering of PAs on optimizing the film morphology and improving the PCE.

A ternary strategy has been demonstrated as a promising method to further boost the performance of organic solar cells (OSCs). Herein, an efficient polymer donor S3 was synthesized and incorporated into a PM6:Y6 system to fabricate ternary OSCs. S3 possesses complementary absorption spectra and good compatibility with PM6, which is beneficial to fine-tune the photon harvesting and morphology of the ternary blend films, resulting in simultaneous enhancement of the short-circuit current density (JSC) and fill factor (FF). In addition, the highest occupied molecular orbital (HOMO) energy level of S3 is slightly lower than that of PM6, which enables lower nonradiative energy loss in ternary OSCs compared with that of PM6-based binary OSCs, leading to higher open-circuit voltage (VOC). The optimized ternary OSCs with 20 wt% S3 in the donors achieve a PCE of 17.53%, which should be among the highest values of ternary OSCs. This work provides an effective approach to fabricate high-performance ternary OSCs by synergizing two well-matched polymer donors.

Small molecular acceptors (SMAs) have gained extensive research attention as they offer many attractive features and enable highly efficient organic solar cells (OSCs) that cannot be achieved using fullerene acceptors. Recently, a new SMA named Y6 was reported, yielding high-performance OSCs with an efficiency of 15.7%. This report has inspired the OSC community to study the structure–property relationship and further modify this important class of materials. In this work, we used the selenium (Se) substitution strategy and developed two new Y6-type SMAs to study the effect of Se atoms on materials properties and device performances. It is found that the introduction of Se atoms can red-shift the absorption spectra and enhance the aggregation of the resulting SMAs. Interestingly, the variations in the substitution positions of Se atoms induce different intramolecular charge transfer within the SMAs. Se substitution at the benzothiadiazole ring is more effective than that at the thienothiophene rings, leading to the increased short-circuit current density (JSC) and higher efficiencies of over 16%. This contribution suggests that appropriate Se substitution is a promising method for optimizing the absorption and aggregation of Y6-type SMAs, thus enhancing their OSC performances.

ConspectusIn the last three decades, p-type (hole-transporting) organic and polymeric semiconductors have achieved great success in terms of materials diversity and device performance, while the development of n-type (electron-transporting) analogues greatly lags behind, which is limited by the scarcity of highly electron-deficient building blocks with compact geometry and good solubility. However, such n-type semiconductors are essential due to the existence of the p-n junction and a complementary metal oxide semiconductor (CMOS)-like circuit in organic electronic devices. Among various electron-deficient building blocks, imide-functionalized arenes, such as naphthalene diimide (NDI) and perylene diimide (PDI), have been proven to be the most promising ones for developing n-type organic and polymeric semiconductors. Nevertheless, phenyl-based NDI and PDI lead to sizable steric hindrance with neighboring (hetero)arenes and a high degree of backbone distortion in the resultant semiconductors, which greatly limits their microstructural ordering and charge transport. To attenuate the steric hindrance associated with NDI and PDI, a novel imide-functionalized heteroarene, bithiophene imide (BTI), was designed; however, the BTI-based semiconductors suffer from high-lying frontier molecular orbital (FMO) energy levels as a result of their electron-rich thiophene framework and monoimide group, which is detrimental to n-type performance.In this Account, we review a series of BTI derivatives developed via various strategies, including ring fusion, thiazole substitution, fluorination, cyanation, and chalcogen substitution, and elaborate the synthesis routes designed to overcome the synthesis challenges due to their high electron deficiency. After structural optimization, these BTI derivatives can not only retain the advantages of good solubility, a planar backbone, and small steric hindrance inherited from BTI but also have greatly suppressed FMO levels. These novel building blocks enable the construction of a great number of n-type organic and polymeric semiconductors, particularly acceptor-acceptor (or all-acceptor)-type polymers, with remarkable performance in various devices, including electron mobility (μe) of 3.71 cm2 V-1 s-1 in organic thin-film transistors (OTFTs), a power conversion efficiency (PCE) of 15.2% in all-polymer solar cells (all-PSCs), a PCE of 20.8% in inverted perovskite solar cells (PVSCs), electrical conductivity (σ) of 0.34 S cm-1 and a power factor (PF) of 1.52 μW m-1 K-2 in self-doped diradicals, and σ of 23.3 S cm-1 and a PF of ∼10 μW m-1 K-2 in molecularly n-doped polymers, all of which are among the best values in each type of device. The structure-property-device performance correlations of these n-type semiconductors are elucidated. The design strategy and synthesis of these novel BTI derivatives provide important information for developing highly electron-deficient building blocks with optimized physicochemical properties. Finally, we offer our insights into the further development of BTI derivatives and semiconductors built from them.

Driven by the exceptional success of 2,2′-bithiophene-3,3′-dicarboximide imide (BTI) for enabling high-performance polymer semiconductors, herein two BTI analogues 2,2′-bifuran-3,3′-dicarboximide (...

A novel nanomaterial, bismuth oxychloride nanoplates (BiOCl NPs), was first applied in organic solar cells (OSCs) as hole transporting layers (HTLs). It is worth noting that the BiOCl NPs can be facilely synthesized at ∼1/200 of the cost of the commercial PEDOT:PSS and well dissolved in green solvents. Different from the PEDOT:PSS interlayer, the deposition of BiOCl HTL is free of post-treatment at elevated temperature, which reduces device fabrication complexity. To demonstrate the universality of BiOCl in improving photovoltaic performance, OSCs containing various representative active layers were investigated. The power conversion efficiencies (PCEs) of the P3HT:PC

High-performance polymer semiconductors generally should have wide absorption, good solution process-ability, and fine-tuned physicochemical properties in order to achieve satisfying photovoltaic performance. Herein, two new alkynyl-functionalized electron donor units, 3-alkyl-3′-alkynyl-2,2′-bithiophene (TRTRy) and 3-alkoxy-3′-alkynyl-2,2′-bithiophene (TORTRy), were invented through the combination of the alkynyl side chain with the alkyl or alkoxy side chain, respectively. Copolymerization of these bithiophenes with difluorobenzothiadiazole (ffBT) afforded polymers ffBT-TRTRy and ffBT-TORTRy, respectively. When applied into polymer solar cells (PSCs), devices using ffBT-TRTRy donor polymer display a maximum power conversion efficiency (PCE) of 2.34% with a short-circuit current (Jsc) of 7.46 mA cm−2, an open circuit voltage (Voc) of 0.93 V, and a fill factor (FF) of 34.0%. The TORTRy containing polymer ffBT-TORTRy affords PSCs with a much improved PCE of 6.60% with a higher Jsc of 15.09 mA cm−2, a larger FF of 58.3%, and a Voc of 0.75 V. The performance improvement of PSC devices using ffBT-TORTRy donor is mainly attributed to the simultaneous realization of higher Jsc and FF, while maintaining a good Voc. The results demonstrate that alkynyl-functionalized H-H bithiophenes are promising building blocks for efficient PSCs.

Two new wide bandgap copolymers PTzTIBDTT and PTzTIBDTT-S based on thiazolothienyl imide (TzTI) and benzodithiophene with a distinct side chain were synthesized and characterized for applications in polymer solar cells (PSCs). The single crystal of the TzTI model compound showed a highly planar backbone with a close π-stacking distance of 3.65 A, a desired structural feature for efficient charge transport. Moreover, the TzTI incorporation can trigger intramolecular noncovalent N⋯S interactions to yield a self-planarized polymer backbone, which should be beneficial for achieving ordered molecular packing and efficient charge transport. Due to its strong electron-withdrawing effect, the incorporation of the TzTI unit largely lowers the polymer HOMO levels to −5.65 and −5.69 eV for PTzTIBDTT and PTzTIBDTT-S, respectively. The PSCs containing the PTzTIBDTT:PC71BM active layer exhibited a promising power conversion efficiency (PCE) of 8.00% with a large Voc of 0.90 V. To the best of our knowledge, the PCE is among the highest values for fullerene PSCs based on an imide-containing polymer donor. This work not only demonstrates that thiazolothienyl imide is a promising building block for constructing high-performance wide bandgap photovoltaic polymer semiconductors, but also reveals that a noncovalent N⋯S conformational lock is an effective molecular design approach for enabling polymer semiconductors with a planar backbone for efficient PSCs.

Thiophene and its derivatives have been extensively used in organic electronics, particularly in the field of polymer solar cells (PSCs). Significant research efforts have been dedicated to modifying thiophene-based units by attaching electron-donating or withdrawing groups to tune the energy levels of conjugated materials. Herein, we report the design and synthesis of a novel thiophene derivative, FE-T, featuring a monothiophene functionalized with both an electron-withdrawing fluorine atom (F) and an ester group (E). The FE-T unit possesses distinctive advantages of both F and E groups, the synergistic effects of which enable significant downshifting of the energy levels and enhanced aggregation/crystallinity of the resulting organic materials. Shown in this work are a series of polymers obtained by incorporating the FE-T unit into a PM6 polymer to fine-tune the energetics and morphology of this high-performance PSC material. The optimal polymer in the series shows a downshifted HOMO and an improved morphology, leading to a high PCE of 16.4% with a small energy loss (0.53 eV) enabled by the reduced non-radiative energy loss (0.23 eV), which are among the best values reported for non-fullerene PSCs to date. This work shows that the FE-T unit is a promising building block to construct donor polymers for high-performance organic photovoltaic cells.

Conductive polyelectrolytes such as P3CT-Na have been widely used as efficient hole-transporting layers (HTLs) in inverted perovskite solar cells (PSCs) due to their high hole mobility. However, the acid-base neutralization reaction is indispensable for preparing such polyelectrolytes and the varied content of cations usually leads to poor reproducibility of the device performance in PSCs. In this work, a commercially available polymer poly[3-(4-carboxybutyl)thiophene-2,5-diyl] (P3CT) was directly applied as an HTL in PSCs for the first time. Encouragingly, it was found that due to the dual functionality of carboxyl groups on side chains, a thin layer of P3CT can not only strongly anchor on ITO electrode and optimize its work function but also show an effective passivation effect toward perovskite active layer. Benefiting from such dual functionality, a uniform perovskite film with better quality was obtained on P3CT. As a result, the P3CT-based PSCs show much lower nonradiative recombination and achieve a champion power conversion efficiency (PCE) of 21.33% with a high fill factor (FF) of 83.6%. Impressively, as the device area is increased to 0.80 cm2, a PCE of 19.65% can still be obtained for the PSCs based on P3CT HTL. Our work provides important strategy for developing HTLs for high-performance PSCs.

Recent advances in the development of polymerized A-D-A-type small-molecule acceptors (SMAs) have promoted the power conversion efficiency (PCE) of all-polymer solar cells (all-PSCs) over 13%. However, the monomer of an SMA typically consists of a mixture of three isomers due to the regio-isomeric brominated end groups (IC-Br(in) and IC-Br(out)). In this work, the two isomeric end groups are successfully separated, the regioisomeric issue is solved, and three polymer acceptors, named PY-IT, PY-OT, and PY-IOT, are developed, where PY-IOT is a random terpolymer with the same ratio of the two acceptors. Interestingly, from PY-OT, PY-IOT to PY-IT, the absorption edge gradually redshifts and electron mobility progressively increases. Theory calculation indicates that the LUMOs are distributed on the entire molecular backbone of PY-IT, contributing to the enhanced electron transport. Consequently, the PM6:PY-IT system achieves an excellent PCE of 15.05%, significantly higher than those for PY-OT (10.04%) and PY-IOT (12.12%). Morphological and device characterization reveals that the highest PCE for the PY-IT-based device is the fruit of enhanced absorption, more balanced charge transport, and favorable morphology. This work demonstrates that the site of polymerization on SMAs strongly affects device performance, offering insights into the development of efficient polymer acceptors for all-PSCs.

Understanding the conformation effect on molecular packing, miscibility, and photovoltaic performance is important to open a new avenue for small-molecule acceptor (SMA) design. Herein, two novel acceptor-(donor-acceptor1-donor)-acceptor (A-DA1D-A)-type asymmetric SMAs are developed, namely C-shaped BDTP-4F and S-shaped BTDTP-4F. The BDTP-4F-based polymer solar cells (PSCs) with PM6 as donor, yields a power conversion efficiency (PCE) of 15.24%, significantly higher than that of the BTDTP-4F-based device (13.12%). The better PCE for BDTP-4F-based device is mainly attributed to more balanced charge transport, weaker bimolecular recombination, and more favorable morphology. Additionally, two traditional A-D-A-type SMAs (IDTP-4F and IDTTP-4F) are also synthesized to investigate the conformation effect on morphology and device performance. Different from the device result above, here, IDTP-4F with S-shape conformation outperforms than IDTTP-4F with C-shape conformation. Importantly, it is found that for these two different types of SMA, the better performing binary blend has similar morphological characteristics. Specifically, both PM6:BDTP-4F and PM6:IDTP-4F blend exhibit perfect nanofibril network structure with proper domain size, obvious face-on orientation and enhance donor-acceptor interactions, thereby better device performance. This work indicates tuning molecular conformation plays pivotal role in morphology and device effciciency, shining a light on the molecular design of the SMAs.

Chemical doping is a key process for investigating charge transport in organic semiconductors and improving certain (opto)electronic devices

Based on dithieno[2,3-b:2′,3′-d]thiophene, three novel helicenes including helicene (rac-1), double helicene (rac-2), and benzohexathia[7]helicene (rac-3), and one bull's horn-shaped benzohexathienoacene (4) have been synthesized and reported in this paper. In the helicenes, the sulfur atoms of terminal thiophenes are inside the helical structures. X-ray crystallographic analysis exhibited the helical configuration of rac-1 and the bull's horn-shaped configuration of 4. Multiple types of intermolecular interactions, including S⋯S, C⋯C and π⋯π interactions, were observed between the adjacent molecules in the crystals of rac-1 and 4. In addition, a remarkable bathochromic shift was found in the absorption behaviors for rac-3 and 4 compared to rac-1; the integrated absorbance in rac-2 is approximately twice that of rac-1.

Narrow-bandgap n-type polymers with high electron mobility are urgently demanded for the development of all-polymer solar cells (all-PSCs). Here, two regioregular narrow-bandgap polymer acceptors, L15 and MBTI, with two electron-deficient segments are synthesized by copolymerizing two dibrominated fused-ring electron acceptors (FREA) with distannylated aromatic imide, respectively. Taking full advantage of the FREA and the imide, both polymer acceptors show narrow bandgap and high electron mobility. Benefiting from the more extended absorption, better backbone ordering, and higher electron mobility than those of its regiorandom analog, the L15-based all-PSC yields a high power conversion efficiency (PCE) of 15.2% when blended with the polymer donor PM6. More importantly, MBTI incorporating a benzothiophene-core FREA segment shows relatively higher frontier molecular orbital levels than L15, forming a cascade-like energy level alignment with L15 and PM6. Based on this, ternary all-PSCs are designed where MBTI is introduced as a guest into the PM6:L15 host system. Thanks to further optimal blend morphology and more balanced charge transport, the PCE is improved up to 16.2%, which is among the highest values for all-PSCs. The results demonstrate that combining an FREA and an aromatic imide to construct regioregular narrow-bandgap polymer acceptors provides an effective approach to fabricate highly efficient all-PSCs.

Imide functionalization is one of the most effective approaches to develop electron-deficient building blocks for constructing n-type organic semiconductors. Driven by the attractive properties of imide-functionalized dithienylbenzodiimide (TBDI) and the promising device performance of TBDI-based polymers, a novel acceptor with increased electron affinity, fluorinated dithienylbenzodiimide (TFBDI), was designed with the hydrogen replaced by fluorine on the benzene core, and the synthetic challenges associated with this highly electron-deficient fluorinated imide building block are successfully overcome. TFBDI showed suppressed frontier molecular orbital energy levels as compared with TBDI. Copolymerizing this new electron-withdrawing TBDI with various donor co-units afforded a series of n-type polymer semiconductors TFBDI-T, TFBDI-Se, and TFBDI-BSe. All these TFBDI-based polymers exhibited a lower-lying lowest unoccupied molecular orbital (LUMO) energy level than the polymer analogue without fluorine. When applied in organic thin-film transistors, three polymers showed unipolar electron transport with large on-current/off-current ratios (

Significant progress has been made in nonfullerene small molecule acceptors (NF‐SMAs) that leads to a consistent increase of power conversion efficiency (PCE) of nonfullerene organic solar cells (NF‐OSCs). To achieve better compatibility with high‐performance NF‐SMAs, the direction of molecular design for donor polymers is toward wide bandgap (WBG), tailored properties, and preferentially ecofriendly processability for device fabrication. Here, a weak acceptor unit, methyl 2,5‐dibromo‐4‐fluorothiophene‐3‐carboxylate (FE‐T), is synthesized and copolymerized with benzo[1,2‐b:4,5‐b′]dithiophene (BDT) to afford a series of nonhalogenated solvent processable WBG polymers P1‐P3 with a distinct side chain on FE‐T. The incorporation of FE‐T leads to polymers with a deep highest occupied molecular orbital (HOMO) level of −5.60−5.70 eV, a complementary absorption to NF‐SMAs, and a planar molecular conformation. When combined with the narrow bandgap acceptor ITIC‐Th, the solar cell based on P1 with the shortest methyl chain on FE‐T achieves a PCE of 11.39% with a large V oc of 1.01 V and a J sc of 17.89 mA cm−2. Moreover, a PCE of 12.11% is attained for ternary cells based on WBG P1, narrow bandgap PTB7‐Th, and acceptor IEICO‐4F. These results demonstrate that the new FE‐T is a highly promising acceptor unit to construct WBG polymers for efficient NF‐OSCs., A series of wide bandgap donor polymers are designed and synthesized by incorporating a monothiophene functionalized with both a fluorine atom and an ester group. Fabricated from nonhalogenated solvent, power conversion efficiencies of 11.39% and 12.11% are achieved for binary and ternary nonfullerene solar cells, respectively.

From the perspective of full cost, this paper uses Coase's transaction cost theory to analyze the causes of crowdsourcing, and on this basis to analyze the applicability of crowdsourcing platform products. At the same time, based on the crowdsourcing platform--zbj.com, we use the big data technology to grasp and analyze the related data of the crowdsourcing platform's successful cases in the past five months, and use the relevant statistical analysis method to categorize and analyze the industry attributes of the top five orders of the success cases of the zbj.com, in order to verify the theory mentioned in the article.

In article number 1801743, Xugang Guo and co‐workers develop two phthalimide‐based polymers featuring a D‐A1‐D‐A2 backbone motif. Eliminating benzodithiophene leads to polymers with substantial mobility. Nonfullerene polymer solar cells utilizing these high‐mobility polymers achieve a remarkable power conversion efficiency >13%. The results demonstrate that phthalimides are excellent building blocks for enabling polymer semiconductors with outstanding solar cell performances and benzodithiophenes are not necessary for constructing such polymers.