Efficient Ternary Polymer Solar Cells Research Articles

18.66% Efficiency of Polymer Solar Cells Employing Two Nonfullerene Acceptors with Fluorine or Chlorine Substitution

Organic semiconducting materials with fluorine or chlorine substitution are commonly designed to prepare efficient polymer solar cells (PSCs) through finely modulating the energy levels and absorption spectra. Herein, two small molecular acceptors with fluorine substitution L8‐BO or chlorine substitution eC9‐2Cl are selected to prepare ternary PSCs with PM6 as polymer donor. The optimal ternary PSCs exhibit a power conversion efficiency of 18.66%, benefiting from the simultaneously increased open‐circuit voltage (VOC) of 0.89 V, short‐circuit current density (JSC) of 26.63 mA cm−2, and fill factor of 78.74% when the content of chlorine substitution eC9‐2Cl is about 20 wt% in acceptors. Fluorinated and chlorinated substitutions can improve the VOC or JSC of the corresponding binary PSCs, which can be recombined into efficient ternary PSCs through optimizing their content in acceptors. Chlorinated materials have special crystalline conditions due to the specific features of the chlorine atoms with large atomic radius and the empty 3d orbits compared to the corresponding fluorinated materials. Adding an appropriate amount of the chlorine substitution eC9‐2Cl further enhances the crystallization and intermolecular interaction of the ternary PSCs, which is beneficial for charge transport in the active layer and for device performance improvement.

Efficient Ternary Polymer Solar Cells with Two Structurally Similar Fullerene-Free Acceptors to Redshift Absorption Peaks and Improve Exciton Dissociation

In this work, Y6 and BTP-eC9 blends are used as a acceptor and D18-Cl as donor to construct ternary PSCs and to boost the power conversion efficiency (PCE) of ternary polymer solar cells (PSCs). Compared with Y6, BTP-eC9 shows a red-shifted absorption peak. As a result, the optimized ternary PSCs show the highest short-circuit current density (JSC). Compared with Y6, BTP-eC9 shows a shallower LUMO level and paly the role of broaden energy level difference. Thus, the blend acceptor endows a high open-circuit voltage (VOC) to the ternary PSCs. In addition, the of Y6 and BTP-eC9 blend as acceptors to enhance crystalline and improve surface and bulk morphology of ternary films, which favor the enhancement of charge carrier mobility and suppression of charge carrier recombination. Thus, the blend of two acceptors with similar molecular structures boosts a higher photovoltaic performance than binary PSCs.

Two Compatible Acceptors as an Alloy Model with a Halogen-Free Solvent for Efficient Ternary Polymer Solar Cells.

A ternary strategy of halogen-free solvent processing can open up a promising pathway for the preparation of polymer solar cells (PSCs) on a large scale and can effectively improve the power conversion efficiency with an appropriate third component. Herein, the green solvent o-xylene (o-XY) is used as the main solvent, and the non-fullerene acceptor Y6-DT-4F as the third component is introduced into the PBB-F:IT-4F binary system to broaden the spectral absorption and optimize the morphology to achieve efficient PSCs. The third component, Y6-DT-4F, is compatible with IT-4F and can form an "alloy acceptor", which can synergistically optimize the photon capture, carrier transport, and collection capabilities of the ternary device. Meanwhile, Y6-DT-4F has strong crystallinity, so when introduced into the binary system as the third component can enhance the crystallization, which is conducive to the charge transport. Consequently, the optimal ternary system based on PBB-F:IT-4F:Y6-DT-4F achieved an efficiency of 15.24%, which is higher than that of the binary device based on PBB-F:IT-4F (13.39%).

Efficient Ternary Polymer Solar Cells with Tunable Crystallinity and Phase Separation of Active Layers via Incorporating GHK-Cu.

The crystallinity of a nonfullerene small-molecule acceptor plays an important function in the bimolecular recombination and carrier transfer of polymer solar cells (PSCs). However, because of the competition between the donor (PBDB-T) and acceptor (ITIC) in processes of phase separation and crystallization, the PBDB-T preferentially forms a crystalline network, which limits the molecular diffusion of ITIC and leads to the weak crystallinity of ITIC, eventually restricting the photoelectric conversion efficiency (PCE) of PSCs. Therefore, in our work, a small-molecule biomaterial, Gly-His-Lys-Cu (SMBM GHK-Cu), is incorporated into binary PBDB-T:ITIC to construct a PBDB-T:ITIC:GHK-Cu ternary system. The addition of GHK-Cu increases ITIC crystallinity and promotes the formation in continuous single-phase domains of PBDB-T and ITIC, which creates an optimized bicontinuous network path to increase and balance charge transmission in PSCs. Meanwhile, GHK-Cu makes energy transfer from GHK-Cu to PBDB-T appreciably efficient, improving the photon capture and exciton-generation rate of PBDB-T. Moreover, it can form a complementary absorption spectrum with PBDB-T and ITIC, which enhances the PCE of ternary devices. Excitingly, the PCE of PSC-based PBDB-T:ITIC is enhanced from 10.28% to 12.07% via incorporating 0.1 wt % GHK-Cu into PBDB-T:ITIC, in which the enhanced open voltage (VOC) is 0.92 V, the short-circuit current (JSC) is 17.87 mA/cm2, and the fill factor (FF) is 73.4%. Meanwhile, the PCE of PSC-based PM6:Y6 is also enhanced from 15.21% for a binary PSC to 17.11% for ternary PSC-based PM6:Y6:0.1 wt % GHK-Cu. This work shows that the cheap and environmentally friendly GHK-Cu has great potential for application in tuning the crystallinity and phase separation of the active layer.

Compatible Acceptors Mediate Morphology and Charge Generation, Transpration, Extraction, and Energy Loss in Efficient Ternary Polymer Solar Cells

Compatible Acceptors Mediate Morphology and Charge Generation, Transpration, Extraction, and Energy Loss in Efficient Ternary Polymer Solar Cells

Two dependent working mechanisms enables efficient ternary polymer solar cells with broad compositional tolerance

Decades of rapid development of polymer solar cells, more and more researchers shift from the direction of pursuing higher power conversion efficiency (PCE) to investigate the properties that satisfy the future commercialization processing conditions. In this work, an efficient D1:D2:A nonfullerene ternary polymer solar cells (PSCs) was fabricated by introducing PM6 in PBTA-PS:ITIC system. With complementary light absorption, structure compatibility, more favorable face-on orientation, optimized morphology and tuned energy levels, the ternary PSCs achieve an enhanced PCE of 11.91% with enhanced short circuit current density (JSC) of 18.58 mA cm−2 and fill factor (FF) of 67.70%, which are higher than that of binary solar cells. It is useful to mention that the ternary devices exhibit with broad compositional tolerance and device stability, which satisfy the large-scale commercialization fabrication conditions. After systematically analysis, two dependent working mechanisms are illustrated in the ternary devices, including FRET channel and charge transfer channel, which benefit the energy transfer and excitons dissociation. Therefore, this work demonstrated a facile method to fabricate efficient two donors ternary PSCs with broad compositional tolerance, higher stability and two dependent working mechanisms, which further promote the commercialization of PSCs.

Efficient Ternary Polymer solar cells based ternary active layer consisting of conjugated polymers and non-fullerene acceptors with power conversion efficiency approaching near to 15.5%

Ternary polymer solar cells employing two polymers (P2, PTB7-Th) and one non-fullerene small molecule acceptor (Y6) were constructed using a conventional structure. The PTB7-Th, P2 and Y6 exhibit complementary absorption spectra therefore, the ternary blend consists of these three can maximize the photon harvesting efficiency which is advantageous to boost of short circuit current density of polymer solar cell. After the optimization of the weight ratios between the two donors and keeping constant the weight concentration of acceptor and following solvent vapor annealing in THF for 40 s, P2:PTB7-Th: Y6 (0.3:0.7:1.5) based polymer solar cells attained the power conversion efficiency of 15.46%, superior to that for polymer solar cells based on binary active layers i.e., P2:Y6 (12.62%) and PTB7-Th:Y6 (12.84%), respectively. The open-circuit voltage for the P2:PTB7-Th:Y6 is about 0.88 V which is in between the values for P2:Y6 (0.94 V) and PTB7-Th:Y6 (0.85 V), consistent with the different highest occupied molecular orbital energy level for P2 (−5.38 eV) and PTB7-Th (−5.27 eV). The enhancement in the short circuit current may be associated with the broader absorption profile of the ternary active layer relative to binary counterparts while the enhanced value of fill factor may be originated from the balanced charge transport, suppressed recombination, and faster charge extraction.

Efficient ternary polymer solar cells by optimizing photogenerated exciton dissociation and photon harvesting with a short wavelength absorption polymer acceptor as the third component

Ternary blend films, obtained by introducing a third component (a second acceptor as the third component) to a binary polymer solar cell (PSC), are a promising ternary strategy because the light absorption range, surface morphology, and charge carrier transport of the photoactive layer may be optimized, as can the energy level alignment between the donor and the acceptor. In this work, acceptors such as the short-wavelength-absorption polymer N2200 and the long-wavelength-absorption small molecule FOIC were combined with the donor PBDB-T-2F to construct ternary blends. The optimized ternary PSC could achieve a power conversion efficiency (PCE) of 13.98%, which is higher than the efficiencies of binary PSCs based on PBDB-T-2F:FOIC (12.65%) and PBDB-T-2F:N2200 (9.36%). The enhanced PCE of the ternary PSC is based on the high electron mobility, balanced charge transport, optimized surface morphology and charge carrier kinetics and the extended light absorption of the ternary photoactive layer, realized by adjusting the ratio of FOIC:N2200. Our results indicate that mixing a polymer acceptor into a binary photoactive layer to form a ternary blend photoactive layer is a valuable strategy for improving photovoltaic performance. • Ternary PSCs were fabricated with F–N2200 as third component materials. • The improvement of charge dynamics process of ternary photoactive layer by ternary strategy. • The improved photon harvesting at the donor–blend acceptor interface.

Review on smart strategies for achieving highly efficient ternary polymer solar cells

Ternary polymer solar cells (PSCs) have been widely demonstrated as an effective method to improve device performance. Meanwhile, the simple fabrication technology can be well kept with a single bulk heterojunction active layer, which is beneficial to the potential industrialization of PSCs. The photovoltaic parameters, such as short-circuit current density, open-circuit voltage, and fill factor, of ternary PSCs can be simultaneously improved by appropriately incorporating the third component, resulting in the increased power conversion efficiency (PCE) compared with the corresponding binary PSCs. To date, the PCE of ternary PSCs has exceeded 17% with the development of effective donors and non-fullerene acceptors. The fundamental designing rules of ternary PSCs are summarized to give some available guidelines for material selection. Next, the recent progress of efficient ternary PSCs based on various types is investigated. Then, some methods are introduced to investigate the working mechanisms of ternary PSCs. At length, the perspective toward the future development of ternary PSCs is discussed.

A minimal benzo[c][1,2,5]thiadiazole-based electron acceptor as a third component material for ternary polymer solar cells with efficiencies exceeding 16.0%

A simple small molecule of BTF is used as a third component in the binary blends of J71:ITIC and PM6:Y6 to achieve efficient ternary polymer solar cells with enhanced PCEs of 12.35% and 16.53%, respectively.

Highly efficient ternary polymer solar cells based on a novel double-cabled third component with the same molecular fragments of donor and acceptor moieties

The red-shifting absorption of non-fullerene acceptor materials is the most important reason for the increasing efficiency of polymer solar cells (PSCs). However, the low absorption of non-fullerene materials in the short-wave direction and the full width at half maximum (FWHM) of the absorption spectra for active layer materials are only around 100 nm, which limits the further improvement of power conversion efficiency (PCE). Herein, we report a novel double-cabled material ITLYBT with the same molecular fragments of donor and acceptor moieties. The absorption spectra of ITLYBT are the superimpose of the donor backbones and the acceptor pendants with nearly 200 nm blue-shift caused by the enhanced steric hindrance, which works as an ideal third component for highly efficient ternary PSCs to broaden and complement the absorption spectra of the photoactive layer. By introducing ITLYBT into PBDB-T-2F:ITIC-4F blend, the ternary device shows enhanced Jsc and Voc, and the over PCE increases from 12.50% to 13.14% due to the optimized phased separation and reduced charge recombination. These results indicate that double-cabled molecule is an ideal third component for construction high performance ternary PSCs.

Small Energy Loss and Broad Energy Levels Offsets Lead to Efficient Ternary Polymer Solar Cells from a Blend of Two Fullerene‐Free Small Molecules as Electron Acceptors

AbstractTernary polymer solar cells (PSCs) are fabricated that consisted of a blend of IEICO‐4F and 3TT‐FIC as electron acceptors and PBDB‐T as an electron donor. The power conversion efficiency (PCE) of ternary PSCs is increased from 9.9% to 11.22% via the blend of IEICO‐4F and 3TT‐FIC as electron acceptors (the ratio of IEICO‐4F:3TT‐FIC is 6:4), which enhances the open‐circuit voltage (VOC) from 0.71 to 0.78 V. The main contribution of the blended acceptor is its broad energy level offset between the donor and acceptor (from 1.26 to 1.30 eV) due to the enhanced lowest unoccupied molecular orbital energy levels of the blended acceptor. Meanwhile, the small energy losses of the ternary photoactive layer (reduced from 0.55 to 0.52 eV) are simultaneously due to the more efficient exciton dissociation and the suppressed charge carrier recombination. This work provides an effective strategy for improving the photovoltaic performance of binary PSCs.

A Carbonylated Terthiophene-Based Twisted Polymer for Efficient Ternary Polymer Solar Cells.

In polymer solar cells (PSCs), it is difficult for twisted conjugated polymers to achieve high power-conversion efficiency (PCE) as donors due to their low charge carrier mobilities and poor bulk heterojunction morphologies. In this work, a new twisted conjugated polymer (P3TCO-1) with excellent solubilities (above 30 mg mL-1 ) in common organic solvents at room temperature is reported. UV-visible absorption spectra and cyclic voltammetry indicate that P3TCO-1 has a wide optical bandgap of 1.90 eV and deep HOMO level of -5.39 eV. In binary PSCs, P3TCO-1:ITIC-based device shows a PCE of 10.11%, with JSC of 17.05 mA cm-2 and FF of 62.89%; P3TCO-1:PC71 BM-based device gives a PCE of 6.67% with JSC of 12.31 mA cm-2 and FF of 58.00%. When the two acceptors of ITIC and PC71 BM are combined, the twisted P3TCO-1-based ternary PSCs exhibit a significantly boosted PCE of up to 11.41%, with a simultaneously improved JSC of 18.16 mA cm-2 and FF of 66.78%. These results can guide the improvement of PCE for twisted conjugated polymer-based PSCs.

Design of wide-bandgap polymers with deeper ionization potential enables efficient ternary non-fullerene polymer solar cells with 13% efficiency

Two regioisomeric wide-bandgap polymers with different nitrogen topologies along the conjugated backbone were developed and applied in non-fullerene polymer solar cells.

Efficient ternary polymer solar cells with dihydronaphthyl-based C60 bisadduct as an third component material

A dihydronaphthyl-based C60 bisadduct (NCBA) acceptor is introduce as a third component to typical PTB7: PC71BM binary polymer solar cells (PSCs). NCBA play bridging role between the lowest unoccupied molecular orbital (LUMO) of PTB7 and PC71BM and provides more routes for charge carrier transfer at the interface between PTB7 and PC71BM, a higher open-circuit voltage (VOC) realize upon addition of NCBA can be achieve relative to the neat PC71BM as an electron acceptor. The strong visible light absorption in the range from 350 to 700 nm of NCBA molecule compared with PC71BM molecule, it has the effect of apparently complementary visible light absorption compare with the binary PTB7:PC71BM thin films. The current density–voltage (J-V) characteristics dependent on incident light intensity were employed and to analyze the effect of NCBA concentration on the charge carrier recombination process of ternary PSCs. The crystallinity and surface morphology of the ternary PTB7:NCBA:PC71BM thin films with NCBA concentration is 15% of blend acceptor is similar to that of the binary PTB7:PC71BM thin films, which guarantees suitable efficient exciton dissociation and charge carrier transport. The transient photovoltage (TPV) and transient photocurrent (TPC) were measured, and the results illustrate the effect of NCBA as the third component materials in terms of higher charge carrier density and long charge carrier lifetime and weaken charge carrier recombination.

Efficient ternary polymer solar cells with a shelf-life stability for longer than 410 days

We have prepared an efficient ternary polymer solar cell incorporating a poly(indacenodithiophene)-based conjugated polymer (PIDTBT), [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)indanone)-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2´,3´-d´]-s-indaceno[1,2-b:5,6-b´]-dithiophene (ITIC). Grazing-incidence wide-angle X-ray scattering (GIWAXS), atomic force microscopy (AFM), and photoluminescence (PL) spectroscopy revealed that intermolecular interactions between the PC71BM and ITIC units disrupted the formation of large ITIC crystals. The ITIC and PC71BM components formed compatible domains that dispersed well within the PIDTBT matrix, providing optimized ternary blends for efficient carrier transport and led to greater photon-to-electron conversion efficiency. Compared with the pre-optimized PC71BM binary device, the ternary device displayed an improvement in short circuit current density (Jsc) from 12.0 ± 0.3 to 14.2 ± 0.5 mA cm–2, due primarily to complementary light harvesting in the visible and near-infrared regions; as a result, the device performance improved by 20%—from 5.5 ± 0.2 to 6.6 ± 0.1% under AM 1.5G (100 mW cm–2) irradiation. Furthermore, the ternary cell exhibited outstanding long-term stability, with its performance remaining high (at 6.8%) after storage for 410 days in a glove box (ISOS-D-1 (shelf lifetime)).

Highly crystalline new benzodithiophene–benzothiadiazole copolymer for efficient ternary polymer solar cells with an energy conversion efficiency of over 10%

A crystalline medium band-gap polymer is prepared. The binary- and ternary-PSCs made with the polymer offered a PCE of 5% and 10%, respectively.

Efficient ternary non-fullerene polymer solar cells with PCE of 11.92% and FF of 76.5%

Highly efficient ternary non-fullerene PSCs were fabricated employing PBDB-T as the donor and mixed ITCPTC:IDT6CN-M as the acceptors.

Two compatible nonfullerene acceptors with similar structures as alloy for efficient ternary polymer solar cells

In this work, we fabricated high efficient ternary PSCs based on two compatible non-fullerene acceptors (IDIC and ITIC) with similar chemical structures and one new D-A-type polymer (PSTZ) donor. By inserting ITIC into the binary PSTZ:IDIC system, the active layer show smooth and gradient energy levels, improved crystallinity and optimized morphologies, which results in efficient exciton separation, charge transport and collection. As a result, the optimal ternary PSCs based on PSTZ:ITIC:IDIC (1:0.1:0.9) exhibited a higher PCE of 11.1% with a Voc of 0.953V, Jsc of 17.4mAcm−2 and FF of 66.9% in comparison with those of binary PSC systems based on PSTZ:IDIC (PCE of 8.06%) or PSTZ:ITIC (PCE of 8.13%). These results indicate that combining two compatible nonfullerene acceptors with similar structures to fabricate ternary PSCs should be a promising strategy to enhance the photovoltaic performance of the PSCs.

Efficient ternary polymer solar cells by doping fullerene derivatives

Here, indene-C60 bisadduct (ICBA) was incorporated into poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-co-3-fluorothieno[3,4-b]thiophene-2-carboxylate]: [6,6]-phenyl-C71-butyric acid-methyl-ester (PTB7-Th:PC71BM) as active layer to fabricate the ternary polymer solar cells (PSCs). The introduction of cascade acceptor ICBA was benefit for energy level alignment and improving interface between polymer donor and fullerene derivatives acceptor while inheriting the major benefit of PTB7-Th and PC71BM, broad and strong absorption and high electron mobility. In the ternary PSCs, the weight ratio of PTB7-Th:fullerene derivatives acceptor was 1:1.5, of which the weight percentage of ICBA in this fullerene derivatives acceptors varied from 0wt% to 100wt%. Introducing around 10wt% ICBA as fullerene derivatives acceptor, the best power conversion efficiency (PCE) was achieved, accompanied by moderated open-circuit voltage (Voc), and maximized short-circuit current (Jsc) and fill factor (FF). Incorporating 10wt% ICBA into PTB7-Th:PC71BM could improve the polymer's spectral absorption intensity and its miscibility with fullerene derivatives acceptor, and enhance the charge transfer from donor to acceptor. Finally, efficiency over 9.2% had been obtained in the simple solar cells based on PTB7-Th:ICBA (10%):PC71BM film.