Ternary Solar Cells Research Articles

Simultaneously improved Jsc and Voc achieving 19.15% efficiency in ternary blend polymer solar cell containing a Y-type acceptor with thiophene based end groups

Simultaneously enhancing the short-circuit current density (Jsc) and open-circuit voltage (Voc) of current state-of-the-art polymer solar cells (PSCs) containing wide bandgap polymers as donors and Y6 derivatives as acceptors is of great challenge but essential for further improvement of the photovoltaic performances. In this work, two Y-type non-fullerene acceptors of BTP-T and BTP-TCl were designed and successfully synthesized with relatively weak electron-accepting thiophene based end groups, where blue-shifted absorption and upshifted LUMO energy levels were achieved to fill the well-known absorption gap at 700 nm of typical binary devices based Y-type molecules and rise the output voltage, respectively. Simultaneously increased Jsc and Voc were achieved in ternary blend devices containing D18:BTP-eC9:BTP-TCl with a significantly improved PCE up to 19.15 %, which is over 7 % increase compared to the binary device. Our results illustrated the great potential of rational design of Y6 derivatives for constructing ternary PSCs to improve their performances.

Adding the third component with similar building blocks to regulate the miscibility of active layer enables high efficient ternary solar cells

Adding the third component with similar building blocks to regulate the miscibility of active layer enables high efficient ternary solar cells

Nonfused Ring Electron Acceptors for Ternary Polymer Solar Cells with Low Energy Loss and Efficiency Over 18.

Ternary polymer solar cells(PSCs) have been identified as an effective approach to improving power conversion efficiency (PCE) of binary PSCs. However, most of the third component, especially Y-series non-fullerene acceptors, is a fused ring acceptor which often requires a rather tedious synthesis and the use of hazardous organostannane reagents. In this work, two nonfused ring acceptors IOEH-4F and IOEH-N2F are synthesized by a green synthetic route and incorporated into PM6:Y6 blend. Encouragingly, the IOEH-4F and IOEH-N2F-based ternary PSCs exhibited more efficient charge transfer, exciton separation, and lower energy loss than PM6:Y6-based PSCs. And the IOEH-4F and IOEH-N2F-based ternary PSCs achieved an impressive PCE of 17.80% and 18.13%, respectively, which are higher than that of PM6:Y6 based PSCs (16.18%). Notably, these PCE values are also the highest PCEs for ternary PSCs including non-fused ring acceptors. Importantly, even when the IOEH-N2F:Y6 ratios increased from 0.05:1.2 to 0.50:1.2, the PCE of IOEH-N2F-based ternary PSCs (16.70%) are still higher than that of PM6:Y6 based PSCs, indicating the great potential for cost saving. It is believed that the findings will help the design of better nonfused ring acceptors and the optimization of corresponding ternary PSCs with cost-saving advantage.

Probing the Effect of Photovoltaic Material on Voc in Ternary Polymer Solar Cells with Non-Fullerene Acceptors by Machine Learning.

The power conversion efficiency (PCE) of ternary polymer solar cells (PSCs) with non-fullerene has a phenomenal increase in recent years. However, improving the open circuit voltage (Voc) of ternary PSCs with non-fullerene still remains a challenge. Therefore, in this work, machine learning (ML) algorithms are employed, including eXtreme gradient boosting, K-nearest neighbor and random forest, to quantitatively analyze the impact mechanism of Voc in ternary PSCs with the double acceptors from the two aspects of photovoltaic materials. In one aspect of photovoltaic materials, the doping concentration has the greatest impact on Voc in ternary PSCs. Furthermore, the addition of the third component affects the energy offset between the donor and acceptor for increasing Voc in ternary PSCs. More importantly, to obtain the maximum Voc in ternary PSCs with the double acceptors, the HOMO and LUMO energy levels of the third component should be around (-5.7 ± 0.1) eV and (-3.6 ± 0.1) eV, respectively. In the other aspect of molecular descriptors and molecular fingerprints in the third component of ternary PSCs with the double acceptors, the hydrogen bond strength and aromatic ring structure of the third component have high impact on the Voc of ternary PSCs. In partial dependence plot, it is clear that when the number of methyl groups is four and the number of carbonyl groups is two in the third component of acceptor, the Voc of ternary PSCs with the double acceptors can be maximized. All of these findings provide valuable insights into the development of materials with high Voc in ternary PSCs for saving time and cost.

Ternary solvent strategy enhancing the photovoltaic performance of ternary polymer solar cells

Ternary solvent strategy enhancing the photovoltaic performance of ternary polymer solar cells

The role of domain size and weight ratio of fullerene and non-fullerene acceptors on performance of PM6:Y6: PCBM ternary solar cell

The role of domain size and weight ratio of fullerene and non-fullerene acceptors on performance of PM6:Y6: PCBM ternary solar cell

Isomerization Directed Molecular Packing toward Suppressing Energy Loss in Nonfullerene Ternary Solar Cells

Organic semiconductors based upon conjugated frameworks are often isomeric and display distinct optoelectronic properties within minor structural variation. In this work, two isomeric nonfullerene acceptors (NFAs) ThMeCl-1 and ThMeCl-2, having the methyl and chlorine atoms attached on different positions of the electron-withdrawing end group, are synthesized and incorporated as the third component in ternary solar cells. Although these NFA isomers exhibit a similar bandgap, energy levels, and energy loss in their PM6 based binary devices, the efficiency enhancements in ternary devices differ significantly. Compared to ThMeCl-1, the incorporation of ThMeCl-2 in PM6:C5-16 solar cells enables less energy loss, leading to an extra 0.03 eV open-circuit voltage gain and a maximum efficiency increase from 17.8 to 18.9%. Grazing-incidence X-ray diffraction and molecular dynamics simulations reveal that this is attributed to the versatile intermolecular π–π stacking forms between ThMeCl-2 and the host NFA, which result in improved charge transport and suppressed recombination. This work provides a rational guidance for controlling the molecular packing in ternary systems to prepare high performance organic photovoltaics.

Crystallinity and phase separation induced morphological modulation for efficient ternary all-polymer solar cells

All-polymer solar cells (all-PSCs) have attracted enormous attention and achieved significant progress in recent years due to their long-term stability and excellent film stretchability. However, the problem of morphology control in bulk-heterojunction (BHJ) films due to highly entangled polymeric chains hinders the further improvement of device performance. In this work, we obtained fine-tuned photoactive layer morphology through reconstructed microstructure induced by steric effects to realize an improved device performance in ternary all-PSCs. The large tetrahexylphenyl substituents on the backbone of naphthalene diimide–indacenodithienothiophene based copolymer acceptor BL-102 bring forth the steric-hindrance effect and influence intermolecular interactions. Therefore, the copolymer BL-102 delivers the property of suppressed self-aggregation, causing reconstructed crystalline features and morphology in blending films. The ternary devices tended to reduce the excessive phase separation by suppressing the aggregation of original polymers but to promote intermixing behaviors. Therefore, the optimal BHJ film manifested a well-formed bi-continuous interpenetrating nanoscale network with a larger π–π stacking coherence length and ordered face-on molecular orientation. Hence, a faster electron transfer (ET) and hole transfer (HT) process combined with balanced charge carrier mobilities can be achieved to enhance the overall device performance. This work provides an effective method to regulate the photoactive layer morphology of all-PSCs through structurally steric hindrance effects and demonstrate the significance of ternary-blending strategy induced nanoscale morphology modulation for fabricating highly efficient all-PSCs.

Improved photovoltaic performance and robustness of all-polymer solar cells enabled by a polyfullerene guest acceptor

Fullerene acceptors typically possess excellent electron-transporting properties and can work as guest components in ternary organic solar cells to enhance the charge extraction and efficiencies. However, conventional fullerene small molecules typically suffer from undesirable segregation and dimerization, thus limiting their applications in organic solar cells. Herein we report the use of a poly(fullerene-alt-xylene) acceptor (PFBO-C12) as guest component enables a significant efficiency increase from 16.9% for binary cells to 18.0% for ternary all-polymer solar cells. Ultrafast optic and optoelectronic studies unveil that PFBO-C12 can facilitate hole transfer and suppress charge recombination. Morphological investigations show that the ternary blends maintain a favorable morphology with high crystallinity and smaller domain size. Meanwhile, the introduction of PFBO-C12 reduces voltage loss and enables all-polymer solar cells with excellent light stability and mechanical durability in flexible devices. This work demonstrates that introducing polyfullerenes as guest components is an effective approach to achieving highly efficient ternary all-polymer solar cells with good stability and mechanical robustness.

Employing fullerene acceptor as the third component to enhance charge transfer for high-efficiency ternary organic solar cells

Ternary organic solar cells (OSCs) based on one donor/one non-fullerene acceptor/one fullerene acceptor have been proven to be a promising method to boost photovoltaic performance. Herein, we report high-efficiency ternary OSCs fabricated with polymer donor PBDB-T, non-fullerene acceptor IDTCN-S and fullerene acceptor PC71BM, which possess complementary absorption spectra. The introduction of PC71BM as the third component into PBDB-T:IDTCN-S binary system can form cascade energy level alignment, which can facilitate charge transfer in the ternary blend films. Meanwhile, the addition of PC71BM also improve the ternary thin film morphology. As a result, ternary solar cells greatly boost the photovoltaic performance from 10.86% (PBDB-T:IDTCN-S) to 12.03%. Our research indicates that fullerene acceptor PC71BM is the efficiently third component for the construction of high-efficiency ternary OSCs.

Over 18% efficiency ternary all-polymer solar cells with high photocurrent and fill factor

Over 18% efficiency ternary all-polymer solar cells with high photocurrent and fill factor

Rationalizing the Influence of Tunable Energy Levels on Quantum Efficiency to Design Optimal Non‐Fullerene Acceptor‐Based Ternary Organic Solar Cells

AbstractNon‐fullerene acceptor (NFA)‐based ternary bulk heterojunction solar cells (TSC) are the most efficient organic solar cells (OSCs) today due to their broader absorption and quantum efficiencies (QE) often surpassing those of corresponding binary blends. The impact on QE of the energetics driving charge transfer at the electron donor:electron acceptor (D/A) interfaces is studied in blends of PBDB‐T‐2F donor with several pairs of lower bandgap NFAs. As in binary blends, the ionization energy offset between donor and acceptor (ΔIE) controls the QE and maximizes for ΔIE > 0.5 eV. However, ΔIE is not controlled by the individual NFAs IEs but by their average, weighted for their blending ratio. Using this property, the QE of a PBDB‐T‐2F:IEICO binary blend that has an insufficient ΔIE for charge generation is improved by adding a deep IE third component: IT‐4F. Combining two NFAs enables to optimize the D/A energy alignment and cells’ QE without molecular engineering.

19.28% Efficiency and Stable Polymer Solar Cells Enabled by Introducing an NIR‐Absorbing Guest Acceptor

AbstractHere, a near‐infrared (NIR)‐absorbing small‐molecule acceptor (SMA) Y‐SeNF with strong intermolecular interaction and crystallinity is developed by combining selenophene‐fused core with naphthalene‐containing end‐group, and then as a custom‐tailor guest acceptor is incorporated into the binary PM6:L8‐BO host system. Y‐SeNF shows a 65 nm red‐shifted absorption compared to L8‐BO. Thanks to the strong crystallinity and intermolecular interaction of Y‐SeNF, the morphology of PM6:L8‐BO:Y‐SeNF can be precisely regulated by introducing Y‐SeNF, achieving improved charge‐transporting and suppressed non‐radiative energy loss. Consequently, ternary polymer solar cells (PSCs) offer an impressive device efficiency of 19.28% with both high photovoltage (0.873 V) and photocurrent (27.88 mA cm−2), which is one of the highest efficiencies in reported single‐junction PSCs. Notably, ternary PSC has excellent stability under maximum‐power‐point tracking for even over 200 h, which is better than its parental binary devices. The study provides a novel strategy to construct NIR‐absorbing SMA for efficient and stable PSCs toward practical applications.

Miscibility driven morphology modulation in ternary solar cells

The PDI-EH molecule was synthesized and integrated into ternary OSCs to obtain miscibility-driven morphology optimization. The relationship between the optimized morphology and charge carrier dynamics was explored by PiFM and TP-AFM characterization.

Synergistic optimization of mechanical and photovoltaic properties in ternary organic solar cells from a two-donor polymer blend

A low-cost and 2D semi-paracrystalline conjugated polymer PTQ10 yields higher efficiency and stretchability in dual donor ternary solar cells.

An efficient enhancement in organic photovoltaics by introducing simple-structured benzo[1,2-b:4,5-b′]dithiophene-based large-bandgap small molecules as the third component

A series simple-structured small molecules of BR-X are used as third components in the binary blends of PM6:Y6 to achieve efficient ternary solar cells with enhanced PCEs up to 17.49%.

Ternary All-Polymer Solar Cells with Efficiency up to 18.14% Employing a Two-Step Sequential Deposition.

Achieving a finely tuned active layer morphology with a suitable vertical phase to facilitate both charge generation and charge transport has long been the main goal for pursuing the highly efficient bulk heterojunction all-polymer solar cells (all-PSCs). Herein, a solution to address the above challenge via synergistically combining the ternary blend strategy and the layer-by-layer (LbL) procedure is proposed. By introducing a synthesized polymer acceptor (PA ), PY-Cl, with higher crystallinity into the designed host acceptor PY-SSe-V, vertical phase distribution and molecular ordering of the LbL-type ternary all-PSCs can be improved in comparison to the LbL-type PM6/PY-SSe-V binary all-PSCs. The formation of the superior bulk microstructure can not only promote charge transport and extraction properties but also reduce energetic disorder and non-radiative recombination loss, thus improving all three photovoltaic parameters simultaneously. Consequently, the PM6/(PY-SSe-V:PY-Cl) ternary all-PSCs show the best efficiency of 18.14%, which is among the highest values reported to date for all-PSCs. This work provides a facile and effective LbL-type ternary strategy for obtaining high-efficiency all-PSCs.

Effect of UV-Light Irradiation on Charge-Accumulation States in PTzBT Polymer Solar Cells

Ternary polymer solar cells based on a polymer PTzBT have received a lot of attention because their power conversion efficiency (PCE) and thermal stability have been greatly improved by adding a small amount of an oligomer ITIC. However, the charge-accumulation states of the PTzBT ternary polymer solar cells have not yet been completely clarified. Here, we report electron spin resonance (ESR) spectroscopy of the PTzBT ternary polymer solar cells to investigate the charge-accumulation states from a microscopic viewpoint with examining the effect of UV-light irradiation. We observed a slight increase in the ESR intensity of the PTzBT cells and layered film samples under simulated solar irradiation with a UV-cut filter. Multiple signals were observed in the PTzBT cells under solar irradiation when the UV-cut filter was removed. Interestingly, no decrease was observed in the ESR signal of ZnO under solar irradiation with the UV-cut filter, although holes in ZnO in the PTzBT cells are known to decrease under solar irradiation. These findings will contribute to a deep understanding of the material properties of polymer solar cells.

End-Group Engineering of Chlorine-Trialkylsiylthienyl Chain-Substituted Small-Molecule Donors for High-Efficiency Ternary Solar Cells.

Ternary architecture has been widely demonstrated as a facile and efficient strategy to boost the performance of organic solar cells (OSCs). However, the rational design of the third component with suitable core and end-group modification is still a challenge. Herein, two new small-molecule (SM) donors BT-CN and BT-ER, featuring the identical conjugated backbone with distinct end group, have been designed, synthesized, and introduced into the PM6:Y6 binary system as the second donor. Both molecules exhibit complementary absorption and good miscibility with PM6, contributing to the nanofibrous phases and strong face-on molecular packing. Importantly, the incorporation of BT-CN/BT-ER has significantly facilitated charge collection and transportation with remarkable suppression of carrier recombination. As a result, ternary OSCs with 20 wt% BT-CN/BT-ER achieved a PCE of 16.8%/17.22% with synchronously increased open-circuit voltage (VOC ), short-circuit current density (JSC ) and fill factor (FF). Moreover, replacing Y6 with L8-BO further improves the PCE to 18.05%/18.11%, indicating the universality of both molecules as the third component. This work demonstrates not only two efficient SM donors with 4,8-bis(4-chloro-5-(tripropylsilyl)thiophen-2-yl) benzo[1,2-b:4,5-b']dithiophene (BDTT-SiCl) as the core but also end group modification strategy to fine-tune the absorption spectrum, molecular packing, and energy levels of SM donors to construct high-performance ternary OSCs.

Simultaneously Enhanced Efficiency and Mechanical Durability in Ternary Solar Cells Enabled by Low‐Cost Incompletely Separated Fullerenes

Front Cover: Article 2200139 by Yuanyuan Kan, Ke Gao and co-workers shows that both improved mechanical durability and efficiency are achieved in the all-PSCs with low-cost incompletely separated fullerenes. A PCE of 16.16% for the ternary device is obtained, significantly higher than those of binary systems, which is among the highest values of all-PSCs. Tech-PCBM slightly disrupts the crystallization of polymers, and disperses well into the amorphous polymer regions of the all-PSC blends, thus facilitating charge transport and improving film ductility simultaneously.