Ternary Organic Photovoltaics Research Articles

CdSe/ZnS quantum dots as a booster in the active layer of distributed ternary organic photovoltaics.

Organic solar cells are a promising candidate for practical use because of their low material cost and simple production procedures. The challenge is selecting materials with the right properties and how they interrelate in the context of manufacturing the device. This paper presents studies on CdSe/ZnS nanodots as dopants in a polymer-fullerene matrix for application in organic solar cells. An assembly of poly(3-hexylthiophene-2,5-diyl) and 6,6-phenyl-C71-butyric acid methyl ester was used as the active reference layer. Absorption and luminescence spectra as well as the dispersion relations of refractive indices and extinction coefficient were investigated. The morphologies of the thin films were studied with atomic force microscopy. The chemical boundaries of the ternary layers were determined by Raman spectroscopy. Based on UPS studies, the energy diagram of the potential devices was determined. The resistivity of the layers was determined using impedance spectroscopy. Simulations (General-Purpose Photovoltaic Device Model) showed a performance improvement in the cells with quantum dots of 0.36-1.45% compared to those without quantum dots.

Dicyclopentadithienothiophene-based non-fullerene acceptors for ternary blend organic photovoltaics

The embedding of non-fullerene acceptor INDCDTT-b16 to PM6:Y6 binary blend devices enables the adjustment of the blend morphology, leading to improvements in carrier mobility, bimolecular/trap-assisted recombination, and charge collection, and promotes a PCE of 16.27%.

Side‐Chain Engineering of Y‐Series Acceptors with Halogenated End‐Group for Efficient Indoor Organic Photovoltaics

AbstractDiverse design strategies for nonfullerene acceptors (NFAs) have aided the development of efficient indoor organic photovoltaics (OPVs) for Internet‐of‐things‐enabled gadgets. However, the side‐chain approach to Y‐series NFAs for fabricating indoor OPVs remains largely unexplored. In this study, the synthesis and photovoltaic characteristics of two side‐chain engineered NFAs with halogenated end‐groups (BTP‐PO‐4F and BTP‐PO‐4Cl) are investigated. NFAs with a Y6 core unit are modified with butyloctyl inner side chains and ethylhexyloxynaphthyl outer side chains. The extended conjugation moiety contributed to red‐shifted absorption, with the chlorination effect presenting a more pronounced influence than fluorination. Further, the outer moiety introduced a slight electron‐withdrawing effect on the Y6 core unit, resulting in energy‐level downshifts. An excellent power conversion efficiency (PCE) of 23.2% is achieved in fluorinated OPVs under a light‐emitting diode lamp (1000 lux). Moreover, integrating the Y6 NFA into the binary blend further enhanced the PCE, reaching 28.3% in PM6:Y6:halogenated NFA ternary OPVs. The panchromatic absorption, high crystallinity, and cascaded energy levels of the ternary blends contribute to achieving a sufficient spectral match and suppress trap‐assisted recombination, ultimately fostering a substantially enhanced fill factor and PCEs under indoor lighting.

Advances in polymerized small-molecule acceptors for improved performance in all-polymer solar cells

This mini-review discusses the progress made in the development of polymerized small-molecule acceptors (PSMAs) for use in all-polymer solar cells (all-PSCs). These PSMAs combine the advantages of both small-molecule acceptors (SMAs) and polymers. Various studies have been conducted using different building blocks to synthesize these acceptors, including indacenodithiophene and indacenodithienothiophene. They exhibit many advantages such as strong absorption in the near infrared region, high electron mobility, and appropriate energy levels, making them good candidate for PSAMs. The improved efficiency of all-PSCs is attributed to several factors, including stronger absorption, improved blend morphology, and redistribution of composition in the film. Additionally, new materials have been incorporated as third components in ternary organic photovoltaics, with some achieving high power conversion efficiencies of up to 17.0%. The development of new acceptors with different building blocks has resulted in improved stability and reproducibility in all-PSCs, paving the way toward high-performance and stable devices. Overall, these developments demonstrate significant potential for further advancements in the field.

Miscibility screening promotes the efficiency and stability of P3HT‐based organic solar cells

AbstractThe power conversion efficiency of organic photovoltaics (OPVs) has witnessed continuous breakthroughs in the past few years, mostly benefiting from the extensive use of a facile ternary blending strategy by blending the host polymer donor:small molecule acceptor mixture with a second small molecule acceptor. Nevertheless, this rather general strategy used in the well‐known PM6 systems fails in constructing high‐performance P3HT‐based ternary OPVs. As a result, the efficiencies of all resulting ternary blends based on a benchmark host P3HT:ZY‐4Cl and a second acceptor are no more than 8%. Employing the mutual miscibility of the binary blends as a guide to screen the second acceptor, here we were able to break the longstanding 10%‐efficiency barrier of ternary OPVs based on P3HT and dual nonfullerene acceptors. With this rational approach, we identified a multifunctional small molecule acceptor BTP‐2Br to simultaneously improve the photovoltaic performance in both P3HT and PM6‐based ternary OPVs. Attractively, the P3HT:ZY‐4Cl:BTP‐2Br ternary blend exhibited a record‐breaking efficiency of 11.41% for P3HT‐based OPVs. This is the first‐ever report that over 11% efficiency is achieved for P3HT‐based ternary OPVs. Importantly, the study helps the community to rely less on trial‐and‐error methods for constructing ternary solar cells.

Embedded Host/Guest Alloy Aggregations Enable High-Performance Ternary Organic Photovoltaics.

Ternary strategy has been intensively studied to improve the power conversion efficiencies of organic photovoltaics. Thereinto, the location of the guest component plays a critical role, but few reports have devoted to this concern. Hereon, we disclose the distribution of LA1 as guest acceptor in varieties of ternary scenarios, and outline the dominating driving forces of managing the guest distribution and operating modes. Governed by appropriate relationship of compatibility, crystallinity, and surface energies between host and guest acceptors, as well as interfacial interactions between donor and dual acceptors, most of the LA1 molecules permeate into the internal of host acceptor phases, forming embedded host/guest alloy-like aggregations. The characteristic distributions greatly optimize the morphologies, maximize energy transfer, and enhance exciton/charge behaviors. Particularly, PM6:IT-4F:LA1 ternary cells afford high efficiency of 15.27% with impressive fill factors (FF) over 81%. The popularization studies further verify the superiority of the LA1-involved alloy structures, and with Y6-family acceptor as host component, an outstanding efficiency of 19.17% was received. The results highlight the importance of guest distribution in ternary systems, and shed light on the governing factors of distributing the guests in ternary cells. This article is protected by copyright. All rights reserved.

A2 -A1 -D-A1 -A2 -Type Nonfullerene Acceptors.

The A2 -A1 -D-A1 -A2 -type molecules consist of one electron-donating (D) core flanked by two electron-accepting units (A1 and A2 ) and have emerged as an essential branch of nonfullerene acceptors (NFAs). These molecules generally possess higher molecular energy levels and wider optical bandgaps compared with those of the classic A-D-A- and A-DA'D-A-type NFAs, owing to the attenuated intramolecular charge transfer effect. These characteristics make them compelling choices for the fabrication of high-voltage organic photovoltaics (OPVs), ternary OPVs, and indoor OPVs. Herein, the recent progress in the A2 -A1 -D-A1 -A2 -type NFAs are reviewed, including the molecular engineering, structure-property relationships, voltage loss (Vloss ), device stability, and photovoltaic performance of binary, ternary, and indoor OPVs. Finally, the challenges and provided prospects are discussed for the further development of this type of NFAs.

Efficient Ternary Indoor Organic Photovoltaics with Fullerene Derivative as the Host Acceptor and Nonfullerene Material as the Guest Acceptor

Efficient Ternary Indoor Organic Photovoltaics with Fullerene Derivative as the Host Acceptor and Nonfullerene Material as the Guest Acceptor

Role of Fullerene ICxA and Non-fullerene Y6 in P3HT-based Ternary Organic Photovoltaics

In recent years, organic photovoltaics (OPVs) have emerged as a promising technology for producing renewable energy. Developing high-performance ternary OPVs requires the discovery of new compounds. In this comprehensive study, we investigated the role of fullerene ICxA and non-fullerene Y6 acceptors as third components in improving the performance of P3HT-based ternary OPVs. Our devices exhibited the good light-harvesting ability of the non-fullerene acceptor and the efficient electron mobility of the fullerene acceptor. Raman and X-ray diffraction (XRD) tests show that increasing the ICxA content increases the molecular order of the ternary thin films, whereas increasing the Y6 content reduces their crystallisation. Results showed the synergistic effects of the weight ratio and the additional component on OPV performance.

Nonfullerene Ternary Organic Photovoltaics with Long-Wavelength Light-Absorption Guest Donor Materials to Improve Photovoltaic Performance

Nonfullerene Ternary Organic Photovoltaics with Long-Wavelength Light-Absorption Guest Donor Materials to Improve Photovoltaic Performance

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.

Indolocarbazole-based small molecules as guest donors for High-Performance ternary organic photovoltaics

This study explores the use of A-D-A or A-D-A′-type small molecule donors that contain an indolocarbazole-based moiety with both symmetric and asymmetric structures as the third component in PM6:Y6 systems to develop ternary organic photovoltaics (OPVs). The guest donor, Ema-OEt, was found to be highly miscible with Y6, resulting in an optimized morphology of an alloy-like structure in the blended film. This, in turn, led to balanced charge transport, high charge mobility, and low charge recombination in the devices, resulting in a synergistic improvement in PV parameters, ultimately leading to an advanced power conversion efficiency (PCE) of 17.64 % in the optimized (PM6:Ema-OEt:Y6 = 1: 0.07: 1.2) ternary device. Furthermore, despite having a higher HOMO energy level than PM6, Ema-OEt, doped as a guest donor in the ternary OPV device, demonstrated a remarkable indoor PCE of 28.67 % under TL84 (Pin = 311.9 μW cm−2). These findings provide an effective and innovative approach to enhance the performance of OPVs.

Recycling the Energy of Indoor Light: Highly Efficient Organic Photovoltaics via a Ternary Strategy

A ternary approach in organic photovoltaics (OPVs) is simple and reliable to effectively tune the optical, electrical, and morphological properties of the photoactive layer for high efficiency as well as long-term stability under 1 sun. However, there have been few papers reporting the benefits of ternary systems for recycling the energy of indoor light, which has narrow emission spectra and weak illumination compared to outdoor light. In this study, by using two compatible donor polymers (PM7 and PM7 D1) with slightly different band gaps and similar chemical structures, we demonstrate a simultaneous modulation of light absorption and molecular packing under ambient conditions, which resulted in efficient indoor OPVs exhibiting power conversion efficiency (PCE) over 20% under 1000 lx of warm white light-emitting diode (2900 K). From morphological analysis, we infer that PM7 serves to seed the nucleation of PM7 D1 in the ternary blend, templating its crystallization and alignment along the PM7 backbone. Such templating effect leads to increased domain spacing and relative degree of crystallinity (rDoC) compared to those of each binary system. We further show that higher rDoC helps suppress both bimolecular and trap-assisted recombination of photogenerated charges in the ternary devices. As a result, the complementary absorption and synergistic molecular assembly of the two donor polymers enhance the short-circuit current density as to increase the average PCEs from 9.6 to 10.3% under 1 sun and from 18.7 to 20.0% under 1000 lx. We envision that our strategy of incorporating both a planar and a flexible donor polymer with similar chemical structures can be generally applicable to attain a high-performance ternary OPV under both 1 sun and indoor light.

The molecular origin of high performance in ternary organic photovoltaics identified using a combination of in situ structural probes

Using a combination of in situ techniques we unravel the role of the tertiary component in the morphological evolution of a model organic photovoltaic ternary blend system and show how this results in a higher efficiency and more stable device.

Stabilized Efficiency of Nonfullerene Organic Solar Cells Under UV‐Filtered Sunlight

The ultraviolet (UV) part in the sunlight is known to cause most damage to organic photovoltaics (OPV). UV filters therefore can improve stability. The lifetime of the UV‐filtered OPV is determined by visible light. Herein, visible sunlight is divided into several bands and modeled by light‐emitting diodes to study the stability of ternary OPV. Poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl‐3‐fluoro)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione)] (PM6) is used as the donor. 2,2′‐((2Z,2′Z)‐((12,13‐bis(2‐ethylhexyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2",3″:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2‐g]thieno[2′,3′:4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (Y6) is used as the acceptor. Another polymer is added as the second donor to improve the stability. As expected, the deep and light blue bands dominate the decay under visible light. After about 1200 h of blue irradiation, the devices enter a relatively stable state up to 3000 h of tracking, in sharp contrast to the continuous decay under UV. No chemical reaction is observed under blue light. Years of outdoor lifetime for nonfullerene OPV are projected with the UV filter.

Ternary organic photovoltaic using long wavelength light absorption polymer as guest donor with enhance photovoltaic performance

Ternary organic photovoltaics (OPVs) are fabricated by PTQ10 as donor materials, Y6 as an acceptor, and PTB7-Th as a guest donor. The lowest unoccupied molecular orbital (LUMO) energy levels of PTB7-Th are deeper than those of PTQ10, and a cascade of LUMO energy levels is formed among the different device materials. The PTQ10:Y6 binary OPVs show an open-circuit voltage (VOC) of 0.870 V, which is relatively higher than that obtained for the ternary OPVs. The decrease in the VOC of the ternary OPVs is mainly ascribed to an upshift in the HOMO energy levels of the blend donor and a narrow energy bandgap. The short-circuit current density (JSC) for the ternary OPVs can be increased from 25.07 mA cm−2 to 26.60 mA cm−2 with a PTB7-Th content of up to 15 wt%, which is mainly attributed to efficient photon harvesting and reduced charge recombination. Therefore, these results indicate that JSC and PCE can be significantly enhanced by the incorporation of PTB7-Th into PTQ10:Y6 binary films despite a significant decrease in VOC.

Manipulating Charge Transfer and Transport via Intermediary Electron Acceptor Channels Enables 19.3% Efficiency Organic Photovoltaics

AbstractBalancing and improving the open‐circuit voltage (Voc) and short‐circuit current density (Jsc) synergistically has always been the critical point for organic photovoltaics (OPVs) to achieve high efficiencies. Here, this work adopts a ternary strategy to regulate the trade‐off between Voc and Jsc by combining the symmetric‐asymmetric non‐fullerene acceptors that differ at terminals and alkyl side chains to build the ternary OPV (TOPV). It is noticed that the reduced energy disorder and the enhanced luminescence efficiency of TOPV enable a mitigated energy loss and a higher Voc. Meanwhile, the third component, which is distributed at the host donor–acceptor interface, acts as the charge transport channel. The prolonged exciton lifetime, the boosted charge mobility, and the depressed charge recombination promote the TOPV to obtain an improved Jsc. Finally, with synergistically improved Voc and Jsc, the TOPV delivers an optimal efficiency of 19.26% (certified as 19.12%), representing one of the highest values reported so far.

Achieving and Understanding of Highly Efficient Ternary Organic Photovoltaics: From Morphology and Energy Loss to Working Mechanism.

Ternary strategy, adding an additional donor (D) or acceptor (A) into conventional binary D:A blend, has shown great potential in improving photovoltaic performances of organic photovoltaics (OPVs) for practical applications. Herein, this review is presented on how efficient ternary OPVs are realized from the aspects of morphology, energy loss, and working mechanism. As to morphology, the role of third component on the formation of preferred alloy-like-phase and vertical-phase, which are driven by the miscibility tuning, is discussed. For energy loss, the effect of the third component on the luminescence enhancement and energetic disordering suppression, which lead to favorable increase of voltage, is presented. Regarding working mechanism, dilution effect and relationships between two acceptors or donor/acceptor, which explain the observed device parameters variations, are analyzed. Finally, some future directions concerning ternary OPVs are pointed out. Therefore, this review can provide a comprehensive understanding of working principles and effective routes for high-efficiency ternary systems, advancing the commercialization of OPVs.

Anion‐Induced Catalytic Reaction in a Solution‐Processed Molybdenum Oxide for Efficient Inverted Ternary Organic Photovoltaics

AbstractSolution‐processed transition metal oxides (TMOs) prepared from complex ion precursors are developed as promising scalable interfacial layers for non‐fullerene organic photovoltaics (OPVs); however, challenges remain in achieving defect‐free and highly oriented metal‐oxygen networks without post‐deposition treatments due to the presence of residual organic metal‐binding ligands in films. Herein, the novel strategy that the problematic organic metal‐binding ligands in TMO precursors can be successfully eliminated by an anion‐induced catalytic reaction (ACR) at room temperature is demonstrated, in which the low‐level anions induce electron redistribution and instability of TMO precursors, expediting binding ligand removal during the hydrolysis reaction. The subsequent condensation process facilitates a dimensionally confined and continuous metal‐oxygen network with a 20‐fold increase in electrical conductivity (from 8.4 × 10−4 to 1.8 × 10−2 S m−1) and superior work function tunability (from 5.1 to 5.3 eV) compared to the pristine film. The ACR‐derived TMO thin film on top of a ternary PBDB‐TF:Y6:PC71BM photoactive layer enables an inverted device configuration with improved efficiency of 17.6%, as well as enhanced stability over 70% of the initial efficiency for up to 100 h AM 1.5G illumination.

Tuning Acceptor Composition in Ternary Organic Photovoltaics–Impact of Domain Purity on Non‐Radiative Voltage Losses

AbstractExaggerated charge losses from excited to charge transfer (CT) and ground states in bulk heterojunction (BHJ) structures results in small voltages (< 1 V) for organic solar cells (OSCs). Characterizing morphology‐voltage loss correlations is difficult due to the complexity of BHJ structures but promises the realization of 20% efficiency for OSCs. By utilizing two similar non‐fullerene acceptors (NFA) in a ternary blend, a pseudo‐binary system is constructed to control the acceptor composition and donor‐acceptor (D‐A) miscibility. Within the framework of miscibility‐morphology controlled device photovoltaics, it is found that higher D‐A miscibility results in enhanced domain purity, which is associated with inefficient excitons dissociation and improves the excited and CT state emission, thereby resulting in enhanced electroluminescence efficiency to reduce the non‐radiative (NR) loss contribution to device voltage. The simple but effective composition mediated morphology control identifies domain purity as one key feature to lower the NR recombination in high quantum yield polymer/NFA blends.