Small Molecule Acceptors Research Articles

Polymerizing M-Series Acceptors for Efficient Polymer Solar Cells: Effect of the Molecular Shape.

Currently, high-performance polymerized small-molecule acceptors (PSMAs) based on ADA-type SMAs are still rare and greatly demanded for polymer solar cells (PSCs). Herein, two novel regioregular PSMAs (PW-Se and PS-Se) are designed and synthesized by using centrosymmetric (linear-shaped) and axisymmetric (banana-shaped) ADA-type SMAs as the main building blocks, respectively. It is demonstrated that photovoltaic performance of the PSMAs can be significantly improved by optimizing the configuration of ADA-type SMAs. Compared to the axisymmetric SMA-based polymer (PS-Se), PW-Se using a centrosymmetric SMA as the main building block exhibits better backbone coplanarity thereby resulting in bathochromically shifted absorption with a higher absorption coefficient, tighter interchain π-π stacking, and more favorable blend film morphology. As a result, enhanced and more-balanced charge transport, better exciton dissociation, and reduced charge recombination are achieved for PW-Se-based devices with PM6 as polymer donor. Benefiting from these positive factors, the optimal PM6:PW-Se-based device exhibits a higher power conversion efficiency (PCE) of 15.65% compared to the PM6:PS-Se-based device (8.90%). Furthermore, incorporation of PW-Se as a third component in the binary active layer of PM6:M36 yields ternary devices with an outstanding PCE of 18.0%, which is the highest value for PSCs based on ADA-type SMAs, to the best of the knowledge.

High-performance intrinsically stretchable organic solar cells based on flexible spacer incorporated dimerized small-molecule acceptors

High power conversion efficiency (PCE), long-term stability, and mechanical robustness are important requirements for the practical applications of organic solar cells (OSCs). Herein, we develop a series of flexible spacer (FS)-incorporated dimerized small-molecule acceptors (DSMAs; DYBT-C0, DYBT-C4, and DYBT-C8) and demonstrate high-performance OSCs with a high PCE of 18.6%, excellent mechanical robustness (crack-onset strain (COS) = 32%) and photostability (t80% lifetime = 1735 h under 1-sun illumination). The incorporation of aliphatic FS units with optimal length effectively reduces the backbone rigidity of the DSMAs and increases the fraction of intermixed domains in the blend films, while maintaining excellent electron transport properties. The DYBT-C4-based OSCs demonstrate higher PCE (18.6%) and stretchability (COS = 32%) compared to the OSCs based on the monomer acceptor (MYT; PCE = 15.9% and COS = 10%) and DSMA without FS units (DYBT-C0; PCE =17.2% and COS = 17%). In addition, due to the reduced diffusion coefficient and higher glass transition temperature of DYBT-C4, the DYBT-C4-based OSCs exhibit photostability significantly higher than that of the OSCs fabricated using MYT (t80% lifetime= 36 h). Consequently, DYBT-C4-based intrinsically stretchable (IS)-OSCs exhibit high device stretchability (strain at PCE80% = 36%) and PCE of 14.3%, demonstrating potential for wearable applications.

Correlation between materials and band‐selective detection in organic photodetectors based on bulk heterojunction

AbstractFor wavelength‐selective photodetection or color discrimination, organic photodetectors (OPDs) can provide significant advantages as solution processability, chemical versatility and functionality. To eliminate the need for commonly used filters, the development of a narrowing approach that simultaneously achieves a selective detection range of less than 50 nm bandwidth and a spectral response of ~20% as efficiency at a required wavelength, remains a real challenge. Herein, different donor polymers and small acceptor molecules have been involved in bulk heterojunctions (BHJs) at 1:1 weight ratio as photoactive layers in specific OPDs. Indeed, the mechanism of charge collection in these OPDs is based on the charge collection narrowing (CCN) principle. In this approach, the detection window can be selected to match the absorption onset of the junction materials used in the BHJ layer. Although essentially based on very thick layers, we are focusing here on OPDs with layer thicknesses of less than 2 μm and post‐deposition annealing temperatures not in excess of 100°C.

Engineering of the Central Core on DBD-Based Materials with Improved Power-Conversion Efficiency by Using the DFT Approach.

Developing proficient organic solar cells with improved optoelectronic properties is still a matter of concern. In the current study, with an aspiration to boost the optoelectronic properties and proficiency of organic solar cells, seven new small-molecule acceptors (Db1-Db7) are presented by altering the central core of the reference molecule (DBD-4F). The optoelectronic aspects of DBD-4F and Db1-Db7 molecules were explored using the density functional theory (DFT) approach, and solvent-state calculations were assessed utilizing TD-SCF simulations. It was noted that improvement in photovoltaic features was achieved by designing these molecules. The results revealed a bathochromic shift in absorption maxima (λmax) of designed molecules reaching up to 776 nm compared to 736 nm of DBD-4F. Similarly, a narrow band gap, low excitation energy, and reduced binding energy were also observed in newly developed molecules in comparison with the pre-existing DBD-4F molecule. Performance improvement can be indicated by the high light-harvesting efficiency (LHE) of designed molecules (ranging from 0.9992 to 0.9996 eV) compared to the reference having a 0.9991 eV LHE. Db4 and Db5 exhibited surprisingly improved open-circuit voltage (V OC) values up to 1.64 and 1.67 eV and a fill factor of 0.9198 and 0.9210, respectively. Consequently, these newly designed molecules can be considered in the future for practical use in manufacturing OSCs with improved optoelectronic and photovoltaic attributes.

3D Crystal Framework Regulation Enables Se‐Functionalized Small Molecule Acceptors Achieve Over 19% Efficiency

AbstractSe‐functionalized small molecule acceptors (SMAs) exhibit unique advantages in constructing materials with near‐infrared absorption, but their photovoltaic performance lags behind that of S‐containing analogs in organic solar cells (OSCs). Herein, two new Se‐containing SMAs, namely Se‐EH and Se‐EHp, are designed and synthesized by regulating bifurcation site of outer alkyl chain, which enables Se‐EH and Se‐EHp to form different 3D crystal frameworks from CH1007. Se‐EH displays tighter π–π stacking and denser packing framework with smaller‐sized pore structure induced by larger steric hindrance effect of outer alkyl chain branched at 2‐position, and a higher dielectric constant of PM6:Se‐EH active layer can be obtained. OSCs based on PM6:Se‐EH achieved very high PCEs of 18.58% in binary and 19.03% in ternary devices with a high FF approaching 80% for Se‐containing SMAs. A more significant alkyl chain steric hindrance effect in Se‐EH adjusts the molecular crystallization to form a favorable nanofiber interpenetrating network with an appropriate domain size to reduce rate of sub‐ns recombination and promote balanced transport of carriers. This work provides references for further design and development of highly efficient Se‐functionalized SMAs.

Tuning polymer-backbone coplanarity and conformational order to achieve high-performance printed all-polymer solar cells

All-polymer solar cells (all-PSCs) offer improved morphological and mechanical stability compared with those containing small-molecule-acceptors (SMAs). They can be processed with a broader range of conditions, making them desirable for printing techniques. In this study, we report a high-performance polymer acceptor design based on bithiazole linker (PY-BTz) that are on par with SMAs. We demonstrate that bithiazole induces a more coplanar and ordered conformation compared to bithiophene due to the synergistic effect of non-covalent backbone planarization and reduced steric encumbrances. As a result, PY-BTz shows a significantly higher efficiency of 16.4% in comparison to the polymer acceptors based on commonly used thiophene-based linkers (i.e., PY-2T, 9.8%). Detailed analyses reveal that this improvement is associated with enhanced conjugation along the backbone and closer interchain π-stacking, resulting in higher charge mobilities, suppressed charge recombination, and reduced energetic disorder. Remarkably, an efficiency of 14.7% is realized for all-PSCs that are solution-sheared in ambient conditions, which is among the highest for devices prepared under conditions relevant to scalable printing techniques. This work uncovers a strategy for promoting backbone conjugation and planarization in emerging polymer acceptors that can lead to superior all-PSCs.

Dimeric Giant Molecule Acceptors Featuring N‐type Linker: Enhancing Intramolecular Coupling for High‐Performance Polymer Solar Cells

AbstractGiant molecular acceptors (GMAs) are typically designed through the conjugated linking of individual small molecule acceptors (SMAs). This design imparts an extended molecular size, elevating the glass transition temperature (Tg) relative to their SMA counterparts. Consequently, it effectively suppresses the thermodynamic relaxation of the acceptor component when blended with polymer donors to construct stable polymer solar cells (PSCs). Despite their merits, the optimization of their chemical structure for further enhancing of device performance remains challenge. Different from previous reports utilizing p‐type linkers, here, we explore an n‐type linker, specifically the benzothiadiazole unit, to dimerize the SMA units via a click‐like Knoevenagel condensation, affording BT‐DL. In comparison with B‐DL with a benzene linkage, BT‐DL exhibits significantly stronger intramolecular super‐exchange coupling, a desirable property for the acceptor component. Furthermore, BT‐DL demonstrates a higher film absorption coefficient, redshifted absorption, larger crystalline coherence, and higher electron mobility. These inherent advantages of BT‐DL translate into a higher power conversion efficiency of 18.49 % in PSCs, a substantial improvement over the 9.17 % efficiency observed in corresponding devices with B‐DL as the acceptor. Notably, the BT‐DL based device exhibits exceptional stability, retaining over 90 % of its initial efficiency even after enduring 1000 hours of thermal stress at 90 °C. This work provides a cost‐effective approach to the synthesis of n‐type linker‐dimerized GMAs, and highlight their potential advantage in enhancing intramolecular coupling for more efficient and durable photovoltaic technologies.

Dimeric Giant Molecule Acceptors Featuring N-type Linker: Enhancing Intramolecular Coupling for High-Performance Polymer Solar Cells.

Giant molecular acceptors (GMAs) are typically designed through the conjugated linking of individual small molecule acceptors (SMAs). This design imparts an extended molecular size, elevating the glass transition temperature (Tg) relative to their SMA counterparts. Consequently, it effectively suppresses the thermodynamic relaxation of the acceptor component when blended with polymer donors to construct stable polymer solar cells (PSCs). Despite their merits, the optimization of their chemical structure for further enhancing of device performance remains challenge. Different from previous reports utilizing p-type linkers, here, we explore an n-type linker, specifically the benzothiadiazole unit, to dimerize the SMA units via a click-like Knoevenagel condensation, affording BT-DL. In comparison with B-DL with a benzene linkage, BT-DL exhibits significantly stronger intramolecular super-exchange coupling, a desirable property for the acceptor component. Furthermore, BT-DL demonstrates a higher film absorption coefficient, redshifted absorption, larger crystalline coherence, and higher electron mobility. These inherent advantages of BT-DL translate into a higher power conversion efficiency of 18.49 % in PSCs, a substantial improvement over the 9.17 % efficiency observed in corresponding devices with B-DL as the acceptor. Notably, the BT-DL based device exhibits exceptional stability, retaining over 90 % of its initial efficiency even after enduring 1000 hours of thermal stress at 90 °C. This work provides a cost-effective approach to the synthesis of n-type linker-dimerized GMAs, and highlight their potential advantage in enhancing intramolecular coupling for more efficient and durable photovoltaic technologies.

Diffusion‐Controlled Morphology Modification via Employing Host/Guest Acceptors to Improve the Stability of Organic Photovoltaics

AbstractTypical bulk‐heterojunction organic photovoltaics (OPV) suffer from instability due to the slowly diffusing small‐molecule acceptors (SMAs) under operational conditions. The originally well‐phase‐separated morphology will undergo SMA self‐aggregation to form over‐purified domains that will deteriorate the OPV performance. This issue can be partially alleviated in sequentially processed OPV cells with a planar‐mixed heterojunction absorber, which is intrinsically more robust due to larger domain sizes and a lower degree of mixing. To further enhance the morphological stability, a strategy is developed to inhibit the disordered molecular diffusion that leads to the loss of crystallinity of SMA domains. Two SMAs, C9‐4F and Y6‐OBO, are incorporated as guest acceptors to form an alloy‐like acceptor with the host acceptor BTP‐eC9. These alloy‐like acceptors improved the crystallinity of the acceptor phase by promoting more ordered molecular packing, effectively restraining the diffusion‐caused loss of SMA crystallinity upon illumination. This approach helps maintain favorable gradients and ultimately ensures OPV morphological stability. Consequently, the derived devices exhibited considerably enhanced stability, with the T80 lifetime of C9‐4F‐based devices reaching ≈790 h and a remarkable ≈1010 h for Y6‐OBO‐based devices, significantly surpassing the ≈450 h observed from binary devices.

Terpolymer Containing a meta-Octyloxy-phenyl-Modified Dithieno[3,2-f:2',3'-h]quinoxaline Unit Enabling Efficient Organic Solar Cells.

With the rapid development of small-molecule electron acceptors, polymer electron donors are becoming more important than ever in organic photovoltaics, and there is still room for the currently available high-performance polymer donors. To further develop polymer donors with finely tunable structures to achieve better photovoltaic performances, random ternary copolymerization is a useful technique. Herein, by incorporating a new electron-withdrawing segment 2,3-bis(3-octyloxyphenyl)dithieno[3,2-f:2',3'-h]quinoxaline derivative (C12T-TQ) to PM6, a series of terpolymers were synthesized. It is worth noting that the introduction of the C12T-TQ unit can deepen the highest occupied molecular orbital energy levels of the resultant polymers. In addition, the polymer Z6 with a 10% C12T-TQ ratio possesses the highest film absorption coefficient (9.86 × 104 cm-1) among the four polymers. When blended with Y6, it exhibited superior miscibility and mutual crystallinity enhancement between Z6 and Y6, suppressed recombination, better exciton separation and charge collection characteristics, and faster hole transfer in the D-A interface. Consequently, the device of Z6:Y6 successfully achieved enhanced photovoltaic parameters and yielded an efficiency of 17.01%, higher than the 16.18% of the PM6:Y6 device, demonstrating the effectiveness of the meta-octyloxy-phenyl-modified dithieno[3,2-f:2',3'-h]quinoxaline moiety to build promising terpolymer donors for high-performance organic solar cells.

High-efficiency flexible organic solar cells with a polymer-incorporated pseudo-planar heterojunction

Organic solar cells (OSCs) are considered as a crucial energy source for flexible and wearable electronics. Pseudo-planar heterojunction (PPHJ) OSCs simplify the solution preparation and morphology control. However, non-halogenated solvent-printed PPHJ often have an undesirable vertical component distribution and insufficient donor/acceptor interfaces. Additionally, the inherent brittleness of non-fullerene small molecule acceptors (NFSMAs) in PPHJ leads to poor flexibility, and the NFSMAs solution shows inadequate viscosity during the printing of acceptor layer. Herein, we propose a novel approach termed polymer-incorporated pseudo-planar heterojunction (PiPPHJ), wherein a small amount of polymer donor is introduced into the NFSMAs layer. Our findings demonstrate that the incorporation of polymer increases the viscosity of acceptor solution, thereby improving the blade-coating processability and overall film quality. Simultaneously, this strategy effectively modulates the vertical component distribution, resulting in more donor/acceptor interfaces and an improved power conversion efficiency of 17.26%. Furthermore, PiPPHJ-based films exhibit superior tensile properties, with a crack onset strain of 12.0%, surpassing PPHJ-based films (9.6%). Consequently, large-area (1 cm2) flexible devices achieve a considerable efficiency of 13.30% and maintain excellent mechanical flexibility with 82% of the initial efficiency after 1000 bending cycles. These findings underscore the significant potential of PiPPHJ-based OSCs in flexible and wearable electronics.

The novel non-fully-fused ring small molecule acceptors: End-capped modification investigation

End-capped modification is an efficacious strategy for developing high-performance acceptor materials. In this paper, the experimentally synthesized A-D-A'-D-A type non-fully-fused ring acceptor IDTBT-4F (R) was used as a reference molecule, and five small molecule acceptors for R1-R5 were investigated by changing R's terminal functional groups. By using DFT/B3PW91/6-31G (d,p) method, the ground-state structures of all molecules were studied. The absorption spectra of these acceptors were gained by the TD-DFT/MPW1PW91/6-31G (d,p) approach. Meanwhile, the charge density difference and transition density matrix were analyzed effectively. It can be observed that, compared to the R molecule, all developed molecules exhibited narrower energy gaps, larger absorption wavelengths, more red-shifted absorption spectra, lower excitation energies, higher dipole moment and greater electron-accepting capacity. The strategy of functional group substitution is superior to halogen substitution in improving the aforementioned parameters. Both terminal π-extension and end-group chlorination strategies can synergistically enhance molecular performance. In addition, we also calculated the electron mobility of the dimers constructed by all the molecules, among which R1 and R4 molecules designed with –COOCH3 functional group substitution and R2 molecule with terminal chlorination achieved superior electron mobility compared to R molecule due to their significant electronic coupling. Overall, the study shows that the designed molecules can be highly effective candidates for applications of organic solar cells.

Real-time monitoring polymerization degree of organic photovoltaic materials toward no batch-to-batch variations in device performance

Polymerization degree plays a vital role in material properties. Previous methodologies of molecular weight control generally cannot suppress or alleviate batch-to-batch variations in device performance, especially in polymer solar cells. Herein, we develop an in-situ photoluminescence system in tandem with a set of analysis and processing procedures to track and estimate the polymerization degree of organic photovoltaic materials. To support the development of this protocol, we introduce polymer acceptor PYT constructed by near-infrared Y-series small molecule acceptors via Stille polymerization, and shed light on the correlations between molecular weight, spectral parameters, and device efficiencies that enable the design of the optical setup and confirm its feasibility. The universality is verified in PYT derivatives with stereoregularity and fluoro-substitution as well as benzo[1,2-b:4,5-b’]dithiophene-based polymers. Overall, our result provides a tool to tailor suitable conjugated oligomers applied to polymer solar cells and other organic electronics for industrial scalability and desired cost reduction.

Near-Infrared Organic Photodetectors with Spectral Response over 1200 nm Adopting a Thieno[3,4-c]thiadiazole-Based Acceptor.

The nonclassical ten-pi-electron 5,5-fused thieno[3,4-c]thiadiazole (TTD) unit is an excellent building block for constructing sub-silicon-band gap organic semiconductors. However, no small molecule acceptor (SMA) materials based on TTD have been reported despite the fact that high-sensitivity near-infrared organic photodetectors (OPDs) are generally achieved by using SMAs. In this work, we report a TTD-based narrow band gap (0.95 eV) SMA material TTD(DTC-2FIC)2 with strong near-infrared absorption. Employing PTB7-Th as a donor, OPDs based on TTD(DTC-2FIC)2 exhibit an optimized responsivity of 0.095 (±0.007) A W-1 at 1100 nm and sustain a decent responsivity of 0.074 (±0.008) A W-1 at 1200 nm. Moreover, a good specific detectivity over 1 × 1011 Jones is achieved at a wavelength of 1200 nm. Detailed characterizations imply that the performance of TTD(DTC-2FIC)2-based OPDs may be substantially improved by choosing lower-mixing donors with shallower energy levels. This work demonstrates that SMAs incorporating TTD as the core unit hold promise for constructing high-sensitivity sub-silicon-band gap OPDs.

Tailoring the Position of Ester Group on N-Alkyl Chains of Benzotriazole-based Small Molecule Acceptors for High-Performance Organic Solar Cells.

Side chain engineering plays a vital role in exploring high-performance small molecule acceptors (SMAs) for organic solar cells (OSCs). In this work, we designed and synthesized a series of A-DA'D-A type SMAs by introducing different N-substituted alkyl and ester alkyl side chains on benzotriazole (BZ) central unit and aimed to investigate the effect of different ester substitution positions on photovoltaic performances. All the new SMAs with ester groups exhibit lower the lowest unoccupied molecular orbital (LUMO) energy levels and more blue-shifted absorption, but relatively higher absorption coefficients than alkyl chain counterpart. After blending with the donor PM6, the ester side chain-based devices demonstrate enhanced charge mobility, reduced amorphous intermixing domain size and long-lived charge transfer state compared to the alkyl chain counterpart, which are beneficial to achieve higher short-circuit current density (Jsc ) and fill factor (FF), simultaneously. Thereinto, the PM6 : BZ-E31 based device achieves a higher power conversion efficiency (PCE) of 18.33 %, which is the highest PCE among the OSCs based on the SMAs with BZ-core. Our work demonstrated the strategy of ester substituted side chain is a feasible and effective approach to develop more efficient SMAs for OSCs.

Polymerized small molecule acceptor based on diketopyrrolopyrrole and IDIC double electron-withdrawing building block for all-polymer solar cells

Polymerized small molecule acceptor based on diketopyrrolopyrrole and IDIC double electron-withdrawing building block for all-polymer solar cells

High‐Performance Ternary Organic Solar Cells with Enhanced Luminescence Efficiency and Miscibility Enabled by Two Compatible Acceptors

AbstractThe ternary strategy has proven to be an effective method for improving the efficiency of organic solar cells (OSCs). However, designing and selecting the third component still pose challenges. In this study, this issue is addressed by focusing on the PBDB‐T:Y18‐F binary system and introducing a new, strong luminescent, asymmetric small‐molecule acceptor (SMA) called L8‐CBIC‐Cl, which shares a similar skeleton with Y18‐F. The similarity in molecular framework facilitates good compatibility between the two acceptors, resulting in the formation of an alloy‐like acceptor phase. Furthermore, the norbornenyl‐modified end group in L8‐CBIC‐Cl contributes to its strong luminescent properties, which in turn leads to a low non‐radiative energy loss and a high open‐circuit voltage. Consequently, the PBDB‐T:L8‐CBIC‐Cl:Y18‐F based ternary devices realize a high power conversion efficiency (PCE) up to 17.01%, which is higher than PBDB‐T:Y18‐F device (14.49%). Importantly, L8‐CBIC‐Cl exhibits a good universality as a guest acceptor in other three binary systems (D18:Y6, D18:BTP‐eC9‐4F, and D18:L8‐BO). The D18:L8‐BO:L8‐CBIC‐Cl device shows an impressive efficiency of 19%. The work demonstrates that employing SMA with a high PLQY and better miscibility with host acceptor as the third component has a great potential for developing high‐efficiency ternary OSCs.

High efficiency and thermally stable ternary all-polymer solar cells achieved by alloyed vinyl-linked polymerized small-molecule acceptors

A high power conversion efficiency (PCE) and long-term stability are crucial for the commercialization of all-polymer solar cells (all-PSCs). In this study, we develop two new polymerized small-molecule acceptors (PSMAs) that include vinylene and fluorinated vinylene linkers (PYBO-VH and PYBO-VF, respectively), to achieve all-PSCs with high PCE (> 18.5%) and thermal stability (T80% lifetime > 1800 h at 120 °C). The PYBO-VF with fluorinated vinylene linkers has more planar backbones than PYBO-VH with vinylene linkers. Thus, PYBO-VF exhibits an 1.5-fold increase in electron mobility (μe = 4.8 × 10−4 cm2 V−1 s−1) and higher glass transition temperature (Tg = 200 °C) compared with PYBO-VH (μe = 3.1 × 10−4 cm2 V−1 s−1 and Tg = 158 °C). As a result, all-PSCs based on PYBO-VF demonstrate superior PCE (17.16%) and thermal stability (T80% lifetime = 2270 h) than those based on PYBO-VH (PCE = 16.44% and T80% lifetime = 1385 h). Importantly, when both PYBO-VH and PYBO-VF are used for constructing ternary all-PSCs, we successfully demonstrate a high-performance and stable all-PSC with a PCE of 18.53% and thermal stability at 120 °C (T80% lifetime = 1840 h). The ternary all-PSCs have one of the best performances among all-PSCs reported to date.

Trade‐Off Break between the Crystallinity and Phase Separation of Donor/Acceptor via a General Two‐Dimensional Transition‐Metal Phosphorus Trichalcogenides Nanoparticle Dopant Concept for Efficient and Stable All‐Polymer Solar Cells

All‐polymer solar cells (all‐PSCs) demonstrate splendid advantages of thermal and mechanical stability. Nevertheless, the rock‐ribbed trade‐off between the crystallinity and phase separation scale of donor/acceptor (D/A) hinder the power conversion efficiency (PCE) improvement of all‐PSCs. Here, a novel two‐dimensional transition‐metal phosphorus trichalcogenides (TMPTCs) namely Cd0.85PS3Li0.3 is intelligently designed and synthesized, and firstly employed as a nanoparticle dopant for PBDB‐T:N2200‐based all‐PSCs. The two‐dimensional Cd0.85PS3Li0.3 possess enormous surface area that can serve as the nucleation center, inducing the crystallinity of D/A without influencing the original phase separation. Such feature significantly boosted the charge transport, PCE (from 7.18% to 8.79%) and stability of PBDB‐T:N2200‐based device. Moreover, the Cd0.85PS3Li0.3 nanoparticle dopant was proved to be universal in non‐fullerene small molecule acceptor (NFSMA)‐based organic solar cells (OSCs), for which the PCE was boosted from 15.05% to 17.27% for PM6:L8‐BO‐based OSCs and from 17.29% to 19.10% for D18:L8‐BO‐based OSCs. These observations exemplify the significance of two‐dimensional TMPTCs nanoparticle dopant as a tool for breaking the rock‐ribbed trade‐off between the crystallinity and phase separation scale of D/A in OSCs, which may open up a special field for making two‐dimensional TMPTCs work in a unprecedented way in OSCs.

Tailoring the Position of Ester Group on N‐Alkyl Chains of Benzotriazole‐based Small Molecule Acceptors for High‐Performance Organic Solar Cells

Side chain engineering plays a vital role in exploring high‐performance small molecule acceptors (SMAs) for organic solar cells (OSCs). In this work, we designed and synthesized a series of A‐DA’D‐A type SMAs by introducing different N‐substituted alkyl and ester alkyl side chains on benzotriazole (BZ) central unit and aimed to investigate the effect of different ester substitution positions on photovoltaic performances. All the new SMAs with ester groups exhibit lower the lowest unoccupied molecular orbital (LUMO) energy levels and more blue‐shifted absorption, but relatively higher absorption coefficients than alkyl chain counterpart. After blending with the donor PM6, the ester side chain‐based devices demonstrate enhanced charge mobility, reduced amorphous intermixing domain size and long‐lived charge transfer state compared to the alkyl chain counterpart, which are beneficial to achieve higher short‐circuit current density (JSC) and fill factor (FF), simultaneously. Thereinto, the PM6:BZ‐E31 based device achieves a higher power conversion efficiency (PCE) of 18.33%, which is the highest PCE among the OSCs based on the SMAs with BZ‐core. Our work demonstrated the strategy of ester substituted side chain is a feasible and effective approach to develop more efficient SMAs for OSCs.