Stability Of Organic Solar Cells Research Articles

How can we improve the stability of organic solar cells from materials design to device engineering?

AbstractAmong a promising photovoltaic technology for solar energy conversion, organic solar cells (OSCs) have been paid much attention, of which the power conversion efficiencies (PCEs) have rapidly surpassed over 20%, approaching the threshold for potential applications. However, the device stability of OSCs including storage stability, photostability and thermal stability, remains to be an enormous challenge when faced with practical applications. The major causes of device instability are rooted in the poor inherent properties of light‐harvesting materials, metastable morphology, interfacial reactions and highly sensitive to external stresses. To get rid of these flaws, a comprehensive review is provided about recent strategies and methods for improving the device stability from active layers, interfacial layers, device engineering and encapsulation techniques for high‐performance OSC devices. In the end, prospectives for the next stage development of high‐performance devices with satisfactory long‐term stability are afforded for the solar community.

Regulating Crystallization of A-D-A-Type Fused Acceptors for Enhanced Stability of Organic Solar Cells: Role of Recognition Interactions with Volatilizable Additives

Regulating Crystallization of A-D-A-Type Fused Acceptors for Enhanced Stability of Organic Solar Cells: Role of Recognition Interactions with Volatilizable Additives

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.

Improved Light Soaking and Thermal Stability of Organic Solar Cells by Robust Interfacial Modification

Improved Light Soaking and Thermal Stability of Organic Solar Cells by Robust Interfacial Modification

Synchronous Regulation of Donor and Acceptor Microstructure using Thiophene‐Derived Non‐Halogenated Solvent Additives for Efficient and Stable Organic Solar Cells

AbstractSolvent additives are pivotal for enhancing the morphology, efficiency, and stability of organic solar cells (OSCs). However, the widely used additive, 1,8‐diiodooctane (DIO), has drawbacks like harmful halogen content and potential OSC degradation. To address these issues, novel non‐halogenated, thienyl‐alkyl‐thienyl structural solvent additives—DTP, DTH, and DTN—featuring varying alkyl linker lengths of (CH2)3, (CH2)6, and (CH2)9, respectively are introduced. Additives with longer alkyl linkers, DTH and DTN, effectively dissolve and strongly interact with both the donor polymer PM6 and acceptor L8‐BO. This dual interaction enables precise tuning of their microstructures, resulting in enhanced crystallinity. Upon incorporating DTH as an additive in OSCs (PM6:L8‐BO), a minimal voltage loss is observed, leading to an impressive efficiency of 18.51%, surpassing the 17.90% achieved with DIO. Furthermore, DTH‐based devices demonstrated superior photostability. In a ternary blend system (PM6:D18‐Cl:L8‐BO), an efficiency of 19.07% is attained, outperforming previous non‐halogenated solvent additive‐based OSCs. Furthermore, employing a non‐halogenated processing solvent combination of toluene and carbon disulfide, a high PCE of 18.82% is achieved. These results underscore the efficacy of designing solvent additives with aromatic and alkyl units, enabling tailored interactions with the donor and acceptor, thereby presenting a robust strategy for optimizing OSC performance and stability.

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.

Recent Progress of Oligomeric Non-Fullerene Acceptors for Efficient and Stable Organic Solar Cells.

Organic solar cells (OSCs) have achieved remarkable power conversion efficiencies (PCEs) of over 19 % in the past few years due to the rapid development of non-fullerene acceptors (NFAs). However, the operational stability remains a great challenge that inhibits their commercialization. Recently, oligomeric NFAs (ONFAs) have attracted great attention, which not only can deliver excellent device performance, but also improve the thermal-/photo- stability of OSCs. This is attributed to the suppressed molecular diffusion of ONFAs associated with their high glass-transition temperature (Tg ) and improved thermodynamic properties of ONFAs. Herein, we focus on investigating the correction between the ONFA chemical structure, material properties, device performance, and stability. In addition, we also try to point out the challenges in synthesizing ONFAs and provide potential directions for future ONFA designs.

Enhancing efficiency and stability of organic solar cells through a simplified four-step synthesis of fully non-fused ring electron acceptor

Design and synthesis of superior cost-effective non-fullerene acceptors (NFAs) are still big challenges for facilitating the commercialization of organic solar cells (OSCs), yet to be realized. Herein, two medium bandgap fully non-fused ring electron acceptors (NFREAs, medium bandgap, i.e., 1.3–1.8 eV), namely PTR-2Cl and PTR-4Cl are synthesized with only four steps by using intramolecular noncovalent interaction central core, structured alkyl side chain orientation linking units and flanking with different electron-withdrawing end group. Among them, PTR-4Cl exhibits increased average electrostatic potential (ESP) difference with polymer donor, enhanced crystallinity and compact π-π stacking compared with the control molecule PTR-2Cl. As a result, the PTR-4Cl-based OSC achieved an impressive power conversion efficiency (PCE) of 14.72%, with a much higher open-circuit voltage (Voc) of 0.953 V and significantly improved fill factor (FF) of 0.758, demonstrating one of the best acceptor material in the top-performing fully NFREA-based OSCs with both high PCE and Voc. Notably, PTR-4Cl-based cells maintain a good T80 lifetime of its initial PCE after over 936 h under a continuous thermal annealing treatment and over 1300 h T80 lifetime without encapsulation. This work provides a cost-effective design strategy for NFREAs on obtaining high Voc, efficient exciton dissociation, and ordered molecular packing and thus high-efficiency and stable OSCs.

Non-Fully Conjugated Dimerized Giant Acceptors with Different Alkyl-Linked Sites for Stable and 19.13 % Efficiency Organic Solar Cells.

Achieving both high power conversion efficiency (PCE) and device stability is a major challenge for the practical development of organic solar cells (OSCs). Herein, three non-fully conjugated dimerized giant acceptors (named 2Y-sites, including wing-site-linked 2Y-wing, core-site-linked 2Y-core, and end-site-linked 2Y-end) are developed. They share the similar monomer precursors but have different alkyl-linked sites, offering the fine-tuned molecular absorption, packing, glass transition temperature, and carrier mobility. Among their binary active layers, D18/2Y-wing has better miscibility, leading to optimized morphology and more efficient charge transfer compared to D18/2Y-core and D18/2Y-end. Therefore, the D18/2Y-wing-based OSCs achieve a superior PCE of 17.73 %, attributed to enhanced photocurrent and fill factor. Furthermore, the D18/2Y-wing-based OSCs exhibit a balance of high PCE and improved stability, distinguishing them within the 2Y-sites. Building on the success of 2Y-wing in binary systems, we extend its application to ternary OSCs by pairing it with the near-infrared absorbing D18/BS3TSe-4F host. Thanks to the complementary absorption within 300-970 nm and further optimized morphology, ternary OSCs obtain a higher PCE of 19.13 %, setting a new efficiency benchmark for the dimer-derived OSCs. This approach of alkyl-linked site engineering for constructing dimerized giant acceptors presents a promising pathway to improve both PCE and stability of OSCs.

Non‐Fully Conjugated Dimerized Giant Acceptors with Different Alkyl‐Linked Sites for Stable and 19.13 % Efficiency Organic Solar Cells

AbstractAchieving both high power conversion efficiency (PCE) and device stability is a major challenge for the practical development of organic solar cells (OSCs). Herein, three non‐fully conjugated dimerized giant acceptors (named 2Y‐sites, including wing‐site‐linked 2Y‐wing, core‐site‐linked 2Y‐core, and end‐site‐linked 2Y‐end) are developed. They share the similar monomer precursors but have different alkyl‐linked sites, offering the fine‐tuned molecular absorption, packing, glass transition temperature, and carrier mobility. Among their binary active layers, D18/2Y‐wing has better miscibility, leading to optimized morphology and more efficient charge transfer compared to D18/2Y‐core and D18/2Y‐end. Therefore, the D18/2Y‐wing‐based OSCs achieve a superior PCE of 17.73 %, attributed to enhanced photocurrent and fill factor. Furthermore, the D18/2Y‐wing‐based OSCs exhibit a balance of high PCE and improved stability, distinguishing them within the 2Y‐sites. Building on the success of 2Y‐wing in binary systems, we extend its application to ternary OSCs by pairing it with the near‐infrared absorbing D18/BS3TSe‐4F host. Thanks to the complementary absorption within 300–970 nm and further optimized morphology, ternary OSCs obtain a higher PCE of 19.13 %, setting a new efficiency benchmark for the dimer‐derived OSCs. This approach of alkyl‐linked site engineering for constructing dimerized giant acceptors presents a promising pathway to improve both PCE and stability of OSCs.

Binary Organic Solar Cells with over 19 % Efficiency and Enhanced Morphology Stability Enabled by Asymmetric Acceptors.

The simultaneous improvement of efficiency and stability of organic solar cells (OSCs) for commercialization remains a challenging task. Herein, we designed asymmetric acceptors DT-C8Cl and DT-C8BTz with functional haloalkyl chains, in which the halogen atoms could induce noncovalent interactions with heteroatoms like O, S, and Se, etc., thus leading to appropriately manipulated film morphology. Consequently, binary devices based on D18: DT-C8Cl achieved a champion power conversion efficiency (PCE) of 19.40 %. The higher PCE of D18: DT-C8Cl could be attributed to the enhanced π-π stacking, improved charge transport, and reduced recombination losses. In addition, the noncovalent interactions induced by haloalkyl chains could effectively suppress unfavorable morphology evolutions and thereby reduce trap density of states, leading to improved thermal and storage stability. Overall, our findings reveal that the rational design of asymmetric acceptors with functional haloalkyl chains is a novel and powerful strategy for simultaneously enhancing the efficiency and stability of OSCs.

Binary Organic Solar Cells with over 19 % Efficiency and Enhanced Morphology Stability Enabled by Asymmetric Acceptors

AbstractThe simultaneous improvement of efficiency and stability of organic solar cells (OSCs) for commercialization remains a challenging task. Herein, we designed asymmetric acceptors DT‐C8Cl and DT‐C8BTz with functional haloalkyl chains, in which the halogen atoms could induce noncovalent interactions with heteroatoms like O, S, and Se, etc., thus leading to appropriately manipulated film morphology. Consequently, binary devices based on D18: DT‐C8Cl achieved a champion power conversion efficiency (PCE) of 19.40 %. The higher PCE of D18: DT‐C8Cl could be attributed to the enhanced π–π stacking, improved charge transport, and reduced recombination losses. In addition, the noncovalent interactions induced by haloalkyl chains could effectively suppress unfavorable morphology evolutions and thereby reduce trap density of states, leading to improved thermal and storage stability. Overall, our findings reveal that the rational design of asymmetric acceptors with functional haloalkyl chains is a novel and powerful strategy for simultaneously enhancing the efficiency and stability of OSCs.

Noncovalent Interaction Boosts Performance and Stability of Organic Solar Cells Based on Giant-Molecule Acceptors.

Designing giant-molecule acceptors is deemed as an up-and-coming strategy to construct stable organic solar cells (OSCs) with high performance. Herein, two giant dimeric acceptors, namely, DYV and DYFV, have been designed and synthesized by linking two Y-series derivatives with a vinyl unit. DYFV exhibits more red-shifted absorption, down-shifted energy levels, and enhanced intermolecular packing than DYV because the intramolecular noncovalent interaction (H···F) of DYFV leads to better coplanarity of the backbone. The D18:DYFV film owns a distinct nanofibrous nanophase separation structure, a more dominant face-on orientation, and more balanced carrier mobilities. Therefore, the D18:DYFV OSC achieves a higher photoelectron conversion efficiency of 17.88% and a longer-term stability with a t80 over 45,000 h compared with the D18:DYV device. The study demonstrates that the intramolecular noncovalent interaction is a superior strategy to design giant-molecule acceptors and boost the photovoltaic performance and stability of the OSCs.

Multiarmed Aromatic Ammonium Salts Boost the Efficiency and Stability of Inverted Organic Solar Cells.

Inverted organic solar cells (OSCs) have attracted much attention because of their outstanding stability, with zinc oxide (ZnO) being commonly used as the electron transport layer (ETL). However, both surface defects and the photocatalytic effect of ZnO could lead to serious photodegradation of acceptor materials. This, in turn, hampers the improvement of the efficiency and stability in OSCs. Herein, we developed a multiarmed aromatic ammonium salt, namely, benzene-1,3,5-triyltrimethanaminium bromide (PhTMABr), for modifying ZnO. This compound possesses mild weak acidity aimed at removing the residual amines present within ZnO film. In addition, the PhTMABr could also passivate surface defects of ZnO through multiple hydrogen-bonding interactions between its terminal amino groups and the oxygen anion of ZnO, leading to a better interface contact, which effectively enhances charge transport. As a result, an efficiency of 18.75% was achieved based on the modified ETL compared to the bare ZnO (PCE = 17.34%). The devices utilizing the modified ZnO retained 87% and 90% of their initial PCE after thermal stress aging at 65 °C for 1500 h and continuous 1-sun illumination with maximum power point (MPP) tracking for 1780 h, respectively. Importantly, the extrapolated T80 lifetime with MPP tracking exceeds 10 000 h. The new class of materials employed in this work to modify the ZnO ETL should pave the way for enhancing the efficiency and stability of OSCs, potentially advancing their commercialization process.

Highly efficient and stable organic solar cells with SnO2 electron transport layer enabled by UV-curing acrylate oligomers

The interfaces between the inorganic metal oxide and organic photoactive layer are of outmost importance for efficiency and stability in organic solar cells (OSCs). Tin oxide (SnO2) is one of the promising candidates for the electron transport layer (ETL) in high-performance inverted OSCs. When a solution-processed SnO2 ETL is employed, however, the presence of interfacial defects and suboptimal interfacial contact can lower the power conversion efficiency (PCE) and operational stability of OSCs. Herein, highly efficient and stable inverted OSCs by modification of the SnO2 surface with ultraviolet (UV)-curable acrylate oligomers (SAR and OCS) are demonstrated. The highest PCEs of 16.6% and 17.0% are achieved in PM6:Y6-BO OSCs with the SAR and OCS, respectively, outperforming a device with a bare SnO2 ETL (PCE 13.8%). The remarkable enhancement of PCEs is attributed to the optimized interfacial contact, leading to mitigated surface defects. More strikingly, improved light-soaking and thermal stability strongly correlated with the interfacial defects are demonstrated for OSCs based on SnO2/UV cross-linked resins compared to OSCs utilizing bare SnO2. We believe that UV cross-linking oligomers will play a key role as interfacial modifiers in the future fabrication of large-area and flexible OSCs with high efficiency and stability.

Amino-Functionalized Graphdiyne Derivative as a Cathode Interface Layer with High Thickness Tolerance for Highly Efficient Organic Solar Cells.

Efficient cathode interfacial materials (CIMs) are essential components for effectively enhancing the performance of organic solar cells (OSCs). Although high-performance CIMs are desired to meet the requirements of various OSCs, potential candidates for CIMs are scarce. Herein, an amino-functionalized graphdiyne derivative (GDY-N) is developed, which represents the first example of GDY that exhibits favorable solubility in alcohol. Utilizing GDY-N as the CIM, an outstanding champion PCE of 19.30% for devices based on the D18-Cl:L8-BO (certified result: 19.05%) is achieved, which is among the highest efficiencies reported to date in OSCs. Remarkably, the devices based on GDY-N exhibit a thickness-insensitive characteristic, maintaining 95% of their initial efficiency even with a film thickness of 25nm. Moreover, the GDY-N displays wide universality and facilitates exceptional stability in OSCs. This work not only enriches the diversity of GDYderivatives, but also demonstrates the feasibility of GDY derivatives as CIMs with high thickness tolerance in OSCs.

Improved Light Soaking and Thermal Stability of Organic Solar Cells by Robust Interfacial Modification

The most widely used material in electron transport layers (ETL) of inverted organic solar cells (iOSCs) is zinc oxide (ZnO). However, the brittleness, inorganic nature, surface defects, and photocatalytic activity of ZnO lead to poor stability in iOSCs. Herein, the light‐soaking and thermal stability of iOSCs are substantially improved by modifying ZnO surface with polyurethane diacrylate (SAR) or urethane acrylate (OCS)‐based ultraviolet (UV) resins. The UV resins significantly reduce the energy barrier, suppress surface defects, and improve interfacial contact between ZnO ETL and the organic photoactive layer. Notably, the SAR and OCS resins mitigate the photocatalytic activity of ZnO, electrical leakage, and interfacial resistance during photoaging of OSCs. As a result, iOSCs based on modified ZnOs retain over 80% of initial efficiency under 1 sun illumination for light soaking 1000 h. Furthermore, SAR and OCS resins on ZnO surfaces form a robust crosslinked network with excellent solvent resistant properties, which result in enhanced thermal stability. These results reveal that this simple and effective approach is a promising procedure to fabricate high‐performance iOSCs.

Reducing the Depletion Region Width at the Anode Interface via a Highly Doped Conjugated Polyelectrolyte Composite for Efficient Organic Solar Cells.

In the realm of organic solar cells (OSCs), the width of the depletion region at the anode interface is a critical factor that adversely impacts the open-circuit voltage (Voc) and the power conversion efficiency (PCE). To address this challenge, a novel approach involving a conjugated polyelectrolyte (CPE)-based composite, PCP-2F-Li:POM, has been developed. This composite serves as a solution-processed hole transport layer (HTL), effectively minimizing the depletion region width in high-performance OSCs. The innovative aspect of PCP-2F-Li:POM lies in its "mutual doping" mechanism. Polyoxometalate (POM) is utilized as a dopant, facilitating the formation of p-doped CPE and n-doped POM within the composite. This results in a substantial increase in doping density, nearly 2 orders of magnitude higher than that observed in unmodified CPE. Consequently, the width of depletion region is markedly reduced, shrinking from 76.4 to 6.0 nm. This reduction plays a pivotal role in enhancing hole transport via the tunneling effect. The practical impact of this development is notable. It leads to an increase in Voc from 0.84 to 0.86 V, thereby contributing significantly to an impressive PCE of 18.04% in OSCs. Moreover, the compatibility of PCP-2F-Li:POM with large-area processing techniques underscores its potential as a viable HTL material for future practical applications. Additionally, its contribution to the enhanced long-term stability of OSCs further bolsters its suitability for practical applications.

Non-halogenated and non-volatile solid additive for improving the efficiency and stability of organic solar cells

A non-halogenated and non-volatile solid additive PID can interact simultaneously with donor and acceptor molecules and stabilize the bulk-heterojunction morphology, increasing the efficiency and thermal stability of organic solar cell devices.

Unveiling the thermal stability of diketopyrrolopyrrole-based terpolymers: a key element for enhanced efficiency and stability of organic solar cells

Thermally stable DPP-based terpolymers with tunable broadband absorption for organic solar cells.