Efficient Ternary Organic Solar Cells Research Articles

Alkyl chain modulation of asymmetric hexacyclic fused acceptor synergistically with wide bandgap third component for high efficiency ternary organic solar cells

Alkyl chain modulation of asymmetric hexacyclic fused acceptor synergistically with wide bandgap third component for high efficiency ternary organic solar cells

Designing a Novel Wide Bandgap Small Molecule Guest for Enhanced Stability and Morphology Mediation in Ternary Organic Solar Cells with over 19.3% Efficiency.

In this study, a novel wide-bandgap small molecule guest material, ITOA, designed and synthesized for fabricating efficient ternary organic solar cells (OSCs) ITOA complements the absorbance of the PM6:Y6 binary system, exhibiting strong crystallinity and modest miscibility. ITOA optimizes the morphology by promoting intensive molecular packing, reducing domain size, and establishing a preferred vertical phase distribution. These features contribute to improved and well-balanced charge transport, suppressed carrier recombination, and efficient exciton dissociation. Consequently, a significantly enhanced efficiency of 18.62% for the ternary device is achieved, accompanied by increased short-circuit current density (JSC), fill factor (FF), and open-circuit voltage (VOC). Building on this success, replacing Y6 with BTP-eC9 leads to an outstanding PCE of 19.33% for the ternary OSCs. Notably, the introduction of ITOA expedites the formation of the optimized morphology, resulting in an impressive PCE of 18.04% for the ternary device without any postprocessing. Moreover, the ternary device exhibits enhanced operational stability under maximum power point (MPP) tracking. This comprehensive study demonstrates that a rationally designed guest molecule can optimize morphology, reduce energy loss, and streamline the fabrication process, essential for achieving high efficiency and stability in OSCs, paving the way for practical commercial applications.

π-Extended giant dimeric acceptor as a third component enables highly efficient ternary organic solar cells with efficiency over 19.2%

Ternary strategy with a suitable third component is a successful strategy to improve the photovoltaic performance of organic solar cells (OSCs). Very recently, Y-series based giant molecule acceptors or oligomerized acceptors have emerged as promising materials for achieving highly efficient and stable binary OSCs, while application as third component for ternary OSCs is limited. Here a novel π-extended giant dimeric acceptor, GDF, is developed based on central Y series core fusion and rigid BDT as linker, and then incorporated into the state-of-the-art PM1:PC6 system to construct ternary OSCs. The GDF has a near planar backbone, resulting in increased π-conjugation, excellent crystallinity, and good electron transport capacity. When GDF is introduced into the PM1:PC6 system, it ensues in a cascade like the lowest unoccupied molecular orbitals (LUMO) energy level alignment, a complementary absorption band with PM1 and PC6, higher and balanced hole and electron mobility, slightly smaller domain size, and a higher exciton dissociation probability for PM1:PC6:GDF (1:1.1:0.1) blend film. As a consequence, the PM1:PC6:GDF (1:1.1:0.1) ternary OSC achieves a champion PCE of 19.22%, with a significantly higher open-circuit voltage and short-circuit current density, compared to 18.45% for the PM1:PC6 (1:1.2) binary OSC. Our findings show that employing a π-extended giant dimeric acceptor as a third component significantly improves the photovoltaic performance of ternary OSCs.

Tailoring the Molecular Planarity of Perylene Diimide-Based Third Component toward Efficient Ternary Organic Solar Cells.

Incorporating a third component into binary organic solar cells (b-OSCs) has provided a potential platform to boost power conversion efficiency (PCEs). However, gaining control over the non-equilibrium blend morphology via the molecular design of the perylene diimide (PDI)-based third component toward efficient ternary organic solar cells (t-OSCs) still remains challenging. Herein, two novel PDI derivatives are developed with tailored molecular planarity, namely ufBTz-2PDI and fBTz-2PDI, as the third component for t-OSCs. Notably, after performing a cyclization reaction, the twisted ufBTz-2PDI with an amorphous character transferred to the highly planar fBTz-2PDI followed by a semi-crystalline character. When incorporating the semi-crystalline fBTz-2PDI into the D18:L8-BO system, the resultant t-OSC achieved an impressive PCE of 18.56%, surpassing the 17.88% attained in b-OSCs. In comparison, the addition of amorphous ufBTz-2PDI into the binary system facilitates additional charge trap sites and results in a deteriorative PCE of 14.37%. Additionally, The third component fBTz-2PDI possesses a good generality in optimizing the PCEs of several b-OSCs systems are demonstrated. The results not only provided a novel A-DA'D-A motif for further designing efficient third component but also demonstrated the crucial role of modulated crystallinity of the PDI-based third component in optimizing PCEs of t-OSCs.

Small molecule donor third component incorporating thieno[3,2-b]thiophene unit enables 19.18% efficiency ternary organic solar cells with improved operational stability

The rational design of the third component to enhance the efficiency and stability of organic solar cell (OSC) is a critical and challenge. Herein, a thieno[3,2-b]thiophene (TT) substituted wide-bandgap small molecule donor BTTC, was designed, synthesized and incorporated into the state-of-the-art PM6:L8-BO binary to construct ternary OSC. The rigid side chain and planar molecule skeleton enables strong crystallinity and complementary absorption with binary system. The introduction of BTTC enhanced the molecular packing, fibril-like film and preferred vertical phase separation, yielding balanced and higher charge transport, more efficient exciton dissociation and suppressed charge recombination. Besides, lower energy loss was attained and thus leading to higher open-circuit voltage (VOC). Consequently, the introduction of BTTC achieved the highest efficiency of 18.8% along with extended operational stability. Furthermore, replacing L8-BO to BTP-eC9 further boosted the ternary PCE to 19.18%, standing one of the best charge management in ternary OSC. This work presents efficient rigid side chain substitution strategy to construct the third component of small molecule donor for high performance ternary OSCs with comprehensively improved photovoltaic parameters. This strategy broadens the selection of guest materials toward realizing the actual commercial application of OSCs.

Efficient Ternary Organic Solar Cells with Suppressed Nonradiative Recombination and Fine-Tuned Morphology via IT-4F as Guest Acceptor.

The large open circuit voltage (VOC) loss is currently one of the main obstacles to achieving efficient organic solar cells (OSCs). In this study, the ternary OSCs comprising PM6:BTP-eC9:IT-4F demonstrate a superior efficiency of 18.2 %. Notably, the utilization of the medium bandgap acceptor IT-4F as the third component results in an exceptionally low nonradiative recombination energy loss of 0.28 V. The desirable energy level cascade is formed among PM6, BTP-eC9, and IT-4F due to the low-lying HOMO and LUMO energy levels of IT-4F. More importantly, the VOC of PM6:BTP-eC9:IT-4F OSCs can reach as high as 0.86 V, which is higher than both binary OSCs without sacrificing JSC and FF. Besides, this strategy proved that IT-4F can not only broaden the absorption range but also work as a morphology modifier in PM6:BTP-eC9:IT-4F OSCs, and there also exists efficient energy transfer between BTP-eC9 and IT-4F. This result provides a promising way to suppress the nonradiative recombination energy loss and realize higher VOC than the two binary OSCs in ternary OSCs to obtain high power conversion efficiencies.

Efficient Dual Mechanisms Boost the Efficiency of Ternary Solar Cells with Two Compatible Polymer Donors to Exceed 19.

Ternary strategyopens a simple avenue to improve the power conversion efficiency (PCE) of organic solar cells (OSCs). The introduction of wide bandgap polymer donors (PDs) as third component canbetter utilize sunlight andimprove the mechanical and thermal stability of active layer. However, efficient ternary OSCs (TOSCs) with two PDs are rarely reported due to inferior compatibility and shortage of efficient PDs match with acceptors. Herein, two PDs-(PBB-F and PBB-Cl) are adopted in the dual-PDs ternary systems to explore the underlying mechanisms and improve their photovoltaic performance. The findings demonstrate that the third components exhibit excellent miscibility with PM6 and are embedded in the host donor to form alloy-like phase. A more profound mechanism for enhancing efficiency through dual mechanisms, that are the guest energy transfer to PM6 and charge transport at the donor/acceptor interface, has been proposed. Consequently, the PM6:PBB-Cl:BTP-eC9 TOSCs achieve PCE of over 19%. Furthermore, the TOSCs exhibit better thermal stability than that of binary OSCs due to the reduction in spatial site resistance resulting from a more tightly entangled long-chain structure. This work not only provides an effective approach to fabricate high-performance TOSCs, but also demonstrates the importance of developing dual compatible PD materials.

A Fused-Ring Electron Acceptor with Phthalimide-Based Ending Groups for Efficient Ternary Organic Solar Cells.

The ternary strategy has been widely applied and recognized to be a valid strategy to enhance the organic photovoltaics' (OPVs) performance. Here, a new fused-ring electron acceptor, BTP-PIO, is designed and synthesized, whose ending groups were replaced by a phthalimide-based group (2-butylcyclopenta[f]isoindole-1,3,5,7(2H,6H)-tetraone) from traditional 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile. The phthalimide-based ending groups endow BTP-PIO with the highest lowest unoccupied molecular orbital (LUMO) level and wider band gap than those of Y6. The ternary device based on PM6:Y6 with BTP-PIO as a guest electron acceptor achieved an elevated open-circuit voltage (VOC) of 0.848 V, a short-circuit current density (JSC) of 27.31 mA cm-2, and a fill factor (FF) of 73.9%, generating a remarkable power conversion efficiency (PCE) of 17.10%, which is superior to the PM6:Y6 binary device of 16.08%. The ternary device exhibited improved charge transfer, suppressed carrier recombination, and lower energy loss. BTP-PIO exhibited a good miscibility with Y6, and an alloy phase between BTP-PIO and Y6 was formed in the ternary bulk heterojunction, leading to better phase separation and molecular packing. This research reveals that ending group modification of Y6 derivatives is a feasible way to produce highly efficient ternary devices.

Over 18% Efficiency Ternary Organic Solar Cells with 300nm Thick Active Layer Enabled by an Oligomeric Acceptor.

The development of high-efficiency thickness-insensitive organic solar cells (OSCs) is crucially important for the mass production of solar panels. However, increasing the active layer thickness usually induces a substantial loss in efficiency. Herein, a ternary strategy in which an oligomer DY-TF is incorporated into PM6:L8-BO system as a guest component is adopted to break this dilemma. The S···F intramolecular noncovalent interactions in the backbone endow DY-TF with a high planarity. Upon the addition of DY-TF, the crystallinity of the blend is effectively improved, leading to increased charge carrier mobility, which is highly desirable in the fabrication of thick-film devices. As a result, thin-film PM6:L8-BO:DY-TF-based device (110nm) shows a power conversion efficiency (PCE) of 19.13%. Impressively, when the active layer thickness increases to 300nm, an efficiency of 18.23% (certified as 17.8%) is achieved, representing the highest efficiency reported for 300 nm thick OSCs thus far. Additionally, blade-coated thick device (300nm) delivers a promising PCE of 17.38%. This work brings new insights into the construction of efficient OSCs with high thickness tolerance, showing great potential for roll-to-roll printing of large-area solar cells.

Highly efficient ternary organic solar cells with excellent open-circuit voltage and fill factor via precisely tuning molecular stacking and morphology

Highly efficient ternary organic solar cells with excellent open-circuit voltage and fill factor via precisely tuning molecular stacking and morphology

PC71BM as Morphology Regulator for Highly Efficient Ternary Organic Solar Cells with Bulk Heterojunction or Layer-by-Layer Configuration.

The ternary strategy is one of the effective methods to regulate the morphology of the active layer in organic solar cells (OSCs). In this work, the ternary OSCs with bulk heterojunction (BHJ) or layer-by-layer (LbL) active layers are prepared by using the polymer donor PM6 and the non-fullerene acceptor L8-BO as the main system and the fullerene acceptor PC71BM as the third component. The power conversion efficiencies (PCEs) of BHJ OSCs and LbL OSCs are increased from 17.10% to 18.02% and from 17.20% to 18.20% by introducing PC71BM into the binary active layer, respectively. The in situ UV-vis absorption spectra indicate that the molecular aggregation and crystallization process can be prolonged by introducing PC71BM into the PM6:L8-BO or PM6/L8-BO active layer. The molecular orientation and molecular crystallinity in the active layer are optimized by introducing the PC71BM into the binary BHJ or LbL active layers, which can be confirmed by the experimental results of grazing incidence wide-angle X-ray scattering. This study demonstrates that the third component PC71BM can be used as a morphology regulator to regulate the morphology of BHJ or LbL active layers, thus effectively improving the performance of BHJ and LbL OSCs.

High efficiency ternary organic solar cells based on two nonfused ring electron acceptors with similar molecular structure

Organic solar cells (OSCs) based on nonfused ring electron acceptors (NFREAs) have shown great potential for future commercial applications due to their reduced synthesis complexity and low cost, and ternary strategy is a promising path for further boosting the development of NFREAs-based OSCs. Herein, two NFREAs FO-4Cl and FO-N with similar molecular structure are employed to fabricate high-performance ternary OSCs via combining a commonly used polymer donor PBDB-T. The PBDB-T:FO-4Cl and PBDB-T:FO-N binary devices can exhibit PCEs of 12.05% and 11.33%, respectively. Incorporating FO-N into the binary blend PBDB-T:FO-4Cl, the PBDB-T:FO-4Cl:FO-N ternary device can achieve a significantly improved PCE of 13.15% with a Voc of 0.87 V, a Jsc of 20.59 mA/cm2 and an FF of 73.02%, which is 9% and 16% higher than the PBDB-T:FO-4Cl and PBDB-T:FO-N based binary devices, respectively. The enhanced Jsc and FF can be ascribed to the enhanced photon harvesting, improved film morphology and high and balanced charge transport. Meanwhile, the Voc of ternary devices are gradually improved after the introduction of the high-lying LUMO component FO-N, which demonstrates that the two acceptors may form alloy state in the blend system. Our results demonstrate that ternary strategy is an effective path for further boosting the performance of NFREA-based OSCs by incorporating isogenous acceptors.

Mitigating the Trade-Off between Non-Radiative Recombination and Charge Transport to Enable Efficient Ternary Organic Solar Cells.

Ternary organic solar cells (OSCs) have attracted intensive studies due to their promising potential for attaining high-performing photovoltaics, whereas there has been an opening challenge in minimizing the open circuit voltage (Voc) loss while retaining the optimal carrier extraction in the multiple mixture absorbers. Here, we systemically investigate a ternary absorber comprised of two acceptors and a donor, in which the resultant Voc and fill factor are varied and determined by the ratios of acceptor components as a result of the unbalance of non-radiative recombination rates and charge transport. The transient absorption spectroscopy and electroluminescence techniques verify two distinguishable charge-transfer (CT) states in the ternary absorber, and the mismatch of non-radiative recombination rates of those two CT states is demonstrated to be associated with the Voc deficit, whilst the high-emissive acceptor molecule delivers inferior electron mobility, resulting in poor charge transport and a subpar fill factor. These findings enable us to optimize the mixture configuration for attaining the maximal-performing devices. Our results not only provide insight into maximizing the photovoltage of organic solar cells but can also motivate researchers to further unravel the photophysical mechanisms underlying the intermolecular electronic states of organic semiconductors.

Two compatible non-fullerene acceptors towards efficient ternary organic photovoltaics

The composition of organic active layers plays significant role in determining the photovoltaic performance of organic solar cells (OSCs). Ternary strategy has shown promising advantages in fabrication for highly efficient OSCs due to its simple process and various donor and acceptor materials. Herein, a famous small molecule acceptor (ITIC) was employed as an assistant acceptor to make efficient ternary organic solar cells (TOSCs). The use of ITIC shows good compatibility and leads to the formation of alloyed state with the host acceptor (BTP-eC9). The middle bandgap of ITIC is also complementary with those of the host active materials (BTP-eC9 and PM6), which will be beneficial for the light-harvesting and thus enhance the photocurrent for OSC devices. Furthermore, the introduction of ITIC can fine-tune the film morphology with continuous nanofiber interpenetrating network, which is great for more balanced charge carrier transport and efficiently suppressed charge recombination. Consequently, a prominent power-conversion-efficiency (PCE) was achieved up to 18.25% with all-around enhancement photovoltaic parameters for the PM6:BTP-eC9:ITIC-based TOSCs.

18.9% Efficiency Ternary Organic Solar Cells Enabled by Isomerization Engineering of Chlorine‐Substitution on Small Molecule Donors

AbstractTernary organic solar cells (OSCs) represent an efficient and facile strategy to further boost the device performance. However, the selection criteria and rational design of the third guest small molecule (SM) material still remain less understood. In this study, two new SM donor isomers, with α‐chlorinated thiophene (αBTCl) and β‐chlorinated thiophene (βBTCl) as side chains, are systematically designed, synthesized and incorporated as a third component in PM6:L8‐BO binary blends. It is noticed that introducing the SM donors guest has extended the absorption of photo‐active layer, induced desired component distribution vertically with enhanced crystallinity and reduced recombination process, leading to increased short‐circuit current (JSC) and improved fill factor. Moreover, due to the synergetic suppressed nonradiative loss and preferable morphology, the ternary OSCs feature improves open‐circuit voltage (VOC). Consequently, an impressive champion power conversion efficiency of 18.96% and 18.55% is achieved by αBTCl‐based and βBTCl‐based ternary OSCs, respectively. Furthermore, a record efficiency of 17.46% is obtained with a 330 nm thickness of αBTCl‐based ternary OSCs. This study demonstrates that molecular isomerization can be a promising design approach for SM donors to construct high‐performance ternary OSCs with simultaneous enhancement of all photovoltaic parameters.

Isomeric acceptors incorporation enables 18.1% efficiency ternary organic solar cells with reduced trap-assisted charge recombination

The donor–acceptor miscibility is one of the most critical factors in controlling the active layer morphologies with multiple components. However, how to practically select the third component with the desired miscibility for efficient ternary organic solar cells remains unresolved. Herein, we demonstrate that the surface energy of thin films could be manipulated by altering the weight ratios of the isomeric acceptors in the blend films and, therefore, the regulation of donor–acceptor miscibility. When the acceptor weight ratio (M−Cl:O-Cl) is 1:0.3, low miscibility (χ = 5.43 × 10-2K) with PM6 is achieved, and the power conversion efficiency of organic solar cells composed of PM6:M−Cl (17.1%) is enhanced to 18.1% (PM6:M−Cl:O-Cl). The increased power conversion efficiency resulted from the surface energy-driven active layer morphology and donor–acceptor phase separations, associated with the significantly lower energetic disorder, trap density, and thus reduced free charge recombination. Our findings underline the significance of the isomeric approach to managing the blend film surface energy and, therefore, the donor–acceptor miscibility for improving the device performance, providing guidelines for the fabrication of high-performed ternary OSCs and material designs.

Efficient ternary organic solar cells enabled by asymmetric nonfullerene electron acceptor with suppressed nonradiative recombination

The open-circuit voltage (Voc) of organic solar cells (OSCs) is still far from the Shockley-Queisser limit due to the large non-radiative voltage loss (ΔVocnonrad). Reducing energy loss (Eloss) to obtain higher Voc without sacrificing Jsc and FF is the key to achieve further improvement in power conversion efficiency (PCE) of OSCs. In this work, we designed and synthesized a new asymmetric nonfullerene acceptor via a dual asymmetric strategy, named as SN-O. Under the synergistic effect of alkoxy chain and nitrogen atom substitution, the LUMO and HOMO energy levels of SN-O are significantly elevated compared to Y6, allowing SN-O to display a high open-circuit voltage with a reduced nonradiative energy loss (ΔEnonrad = 0.177 eV). The alkoxy side chain of SN-O brings an intramolecular conformational locking effect and the large dipole moment of asymmetric molecules facilitate the aggregation properties in thin films. The good miscibility allows Y6 and SN-O to form alloy acceptor attributing to the similar chemical structures. The addition of SN-O as the third component into the D18:Y6 system showed a significant reduction in the nonradiative energy loss and a favorable blend film morphology, thus improves exciton dissociation, charge transport and collection. Consequently, a high PCE of 18.3% was achieved for D18:Y6:SN-O ternary system with simultaneously enhancement of Voc, Jsc and FF, which is much higher than that of the binary devices.

18.7% Efficiency Ternary Organic Solar Cells Using Two Non-Fullerene Acceptors with Excellent Compatibility

In this work, a series of ternary organic solar cells (OSCs) were prepared with polymer PM6 as a donor and two non-fullerene materials, BTP-eC9 and ITIC-Th, with excellent compatibility as acceptors. The open-circuit voltage (VOC) of ternary OSCs is found to monotonically increase with increasing content of ITIC-Th, implying the formation of an alloying state between BTP-eC9 and ITIC-Th. Furthermore, the incorporation of ITIC-Th can effectively minimize energy loss, which effectively improves the VOC of ternary OSCs. Consequently, a remarkable power conversion efficiency (PCE) of 18.7% with a short-circuit current density (JSC) of 28.0 mA cm–2, a VOC of 0.87 V, and a fill factor (FF) of 77.0% is achieved from the optimal ternary OSCs with 15 wt % ITIC-Th in acceptors. Comprehensive characterizations show that the enhanced JSC and FF are likely due to enhanced photon harvesting, effective exciton dissociation, and balanced charge transport in the optimal ternary active layers. The findings provide a hopeful way to further improve the OSC performance by employing a ternary strategy with two compatible non-fullerene materials as acceptors.

Enhancing intermolecular packing and light harvesting through asymmetric non-fullerene acceptors for achieving 18.7% efficiency ternary organic solar cells

An asymmetric non–fullerene acceptor (AFIC) was deliberately developed as the third component for ternary organic solar cells. The ternary device with 10 wt% of AFIC achieved an outstanding efficiency of 18.7%.

All-small-molecule efficient ternary organic solar cells employing a coumarin donor and two fullerene-free acceptors

A ternary organic solar cell composed of two fullerene-free acceptors and a coumarin donor attained appropriate nano-scale phase separation, achieving a PCE of 15.54%.