Performance Of Organic Solar Cells Research Articles

Designing A–D–A Type Fused‐Ring Electron Acceptors with a Bulky 3D Substituent at the Central Donor Core to Minimize Non‐Radiative Losses and Enhance Organic Solar Cell Efficiency

AbstractDesigning and synthesizing narrow band gap acceptors that exhibit high photoluminescence quantum yield (PLQY) and strong crystallinity is a highly effective, yet challenging, approach to reducing non‐radiative energy losses (▵Enr) and boosting the performance of organic solar cells (OSCs). We have successfully designed and synthesized an A–D–A type fused‐ring electron acceptor, named DM‐F, which features a planar molecular backbone adorned with bulky three‐dimensional camphane side groups at its central core. These bulky substituents effectively hinder the formation of H‐aggregates of the acceptors, promoting the formation of more J‐aggregates and notably elevating the PLQY of the acceptor in the film. As anticipated, DM‐F showcases pronounced near‐infrared absorption coupled with impressive crystallinity. Organic solar cells (OSCs) leveraging DM‐F exhibit a high EQEEL value and remarkably low ▵Enr of 0.14 eV‐currently the most minimal reported value for OSCs. Moreover, the power conversion efficiency (PCE) of binary and ternary OSCs utilizing DM‐F has reached 16.16 % and 20.09 %, respectively, marking a new apex in reported efficiency within the OSCs field. In conclusion, our study reveals that designing narrow band gap acceptors with high PLQY is an effective way to reduce ▵Enr and improve the PCE of OSCs.

Designing A-D-A Type Fused-Ring Electron Acceptors with a Bulky 3D Substituent at the Central Donor Core to Minimize Non-Radiative Losses and Enhance Organic Solar Cell Efficiency.

Designing and synthesizing narrow band gap acceptors that exhibit high photoluminescence quantum yield (PLQY) and strong crystallinity is a highly effective, yet challenging, approach to reducing non-radiative energy losses (▵Enr) and boosting the performance of organic solar cells (OSCs). We have successfully designed and synthesized an A-D-A type fused-ring electron acceptor, named DM-F, which features a planar molecular backbone adorned with bulky three-dimensional camphane side groups at its central core. These bulky substituents effectively hinder the formation of H-aggregates of the acceptors, promoting the formation of more J-aggregates and notably elevating the PLQY of the acceptor in the film. As anticipated, DM-F showcases pronounced near-infrared absorption coupled with impressive crystallinity. Organic solar cells (OSCs) leveraging DM-F exhibit a high EQEEL value and remarkably low ▵Enr of 0.14 eV-currently the most minimal reported value for OSCs. Moreover, the power conversion efficiency (PCE) of binary and ternary OSCs utilizing DM-F has reached 16.16 % and 20.09 %, respectively, marking a new apex in reported efficiency within the OSCs field. In conclusion, our study reveals that designing narrow band gap acceptors with high PLQY is an effective way to reduce ▵Enr and improve the PCE of OSCs.

Correlating crystallinity and performance in single-component organic solar cells based on double-cable conjugated polymers

The thin film morphology of double-cable conjugated polymers is critical to the performance of single-component organic solar cells (SCOSCs). Here, we explore the effect of thin film crystallinity on device performance by varying the thermal annealing temperature used during device fabrication. Our investigations reveal that a moderate annealing temperature of 150 °C optimizes the power conversion efficiency in SCOSCs. Although higher annealing temperatures leads to increased crystalline order, a decrease in device performance is observed, attributed to imbalanced carrier transport and increased charge recombination. Additionally, the progressive decrease in the open-circuit voltage of these cells with increasing annealing temperature is linked to augmented non-radiative voltage losses, stemming from the increase in film crystallinity. This study underscores the critical necessity of achieving a delicate optimization of film microstructure in order to maximize the efficiency of SCOSCs, while also delineating prospective avenues for refining the molecular design and processing of double-cable polymers to bolster solar cell performance.

Theoretical study on the effect of end groups and core ring numbers in non-fullerene acceptors for organic solar cells

Modifying the skeleton, side chains and end groups of non-fullerene acceptors (NFAs) is important approach to improve the photovoltaic performance of organic solar cells. We selected PBDB-T as the donor and INIC, INIC1, INIC2, ITCC, ITCPTC and ITIC as the acceptors in order to study the difference in NFAs. The geometries, electronic structures, excited state properties, excited-state lifetimes and rate constants of charge transfer (CT), charge recombination (CR) and exciton dissociation (ED) processes of the monomers and PBDB-T:NFA complexes have been investigated by means of density functional theory and time-dependent density functional theory. The research reveals that fluorination of end groups, thienyl substitution and increase in the number of central rings result in the decrease in the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital. Fluorine substitution and increase in central ring numbers cause redshift of the absorption spectrum for NFAs. NFAs with fluorine substitution have a larger maximum electrostatic potential, which facilitates CT at the donor:NFA heterojunction interfaces. Fluorine substitution and thienyl substitution decrease the NFA's CT distances, indicating that both fluorine and thienyl substitutions affect the CT rate. Fluorine substitution, thienyl modification of end groups and increase in central ring numbers also reduce the exciton binding energy, which is beneficial for decreasing CR and improving ED efficiency.

High-Performance PM6:Y6-Based Ternary Solar Cells with Enhanced Open Circuit Voltage and Balanced Mobilities via Doping a Wide-Band-Gap Amorphous Acceptor.

Great progress has been made in organic solar cells (OSCs) in recent years, especially after the report of the highly efficient small-molecule electron acceptor Y6. However, the relatively low open circuit voltage (VOC) and unbalanced charge mobilities remain two issues that need to be resolved for further improvement in the performance of OSCs. Herein, a wide-band-gap amorphous acceptor IO-4Cl, which possessed a shallower lowest unoccupied molecular orbital (LUMO) energy level than Y6, was introduced into the PM6:Y6 binary system to construct a ternary device. The mechanism study revealed that the introduced IO-4Cl was alloyed with Y6 to prevent the overaggregation of Y6 and offer dual channels for effective hole transportation, resulting in balanced hole and electron mobilities. Taking these advantages, an enhanced VOC of 0.894 V and an improved fill factor of 75.58% were achieved in the optimized PM6:Y6:IO-4Cl-based ternary device, yielding a promising power conversion efficiency (PCE) of 17.49%, which surpassed the 16.72% efficiency of the PM6:Y6 binary device. This work provides an alternative solution to balance the charge mobilities of PM6:Y6-based devices by incorporating an amorphous high-performance LUMO A-D-A small molecule as the third compound.

Realizing over 18% Efficiency for M‐Series Acceptor‐Based Polymer Solar Cells by Improving Light Utilization

AbstractM‐series molecules are one kind of promising acceptor‐donor‐acceptor (A‐D‐A)‐type acceptors for constructing high‐performance organic solar cells (OSCs). However, their power conversion efficiencies (PCEs) are lagging behind that of current state‐of‐the‐art OSCs, limited by the relatively low fill factor (FF) and photocurrent. Herein, combined strategies of layer‐by‐layer (LBL) deposition and interface engineering are conducted to systematically improve light utilization and thus PCEs for M36‐based OSCs. Through choosing a proper processing solvent, a PCE of 17.3% with an FF of 77.9% is achieved for the resulting LBL devices, much higher than those (15.9%/74.0%) from the blend‐casting devices. The improvement is assigned to the favorable morphological evolution that facilitates carrier generation and transport as well as reduces charge recombination. More importantly, light‐harvesting of the active layers can be enhanced upon employing a self‐assembled monolayer of (2‐(9H‐carbazol‐9‐yl)ethyl)phosphonic acid (2PACz) instead of the widely used PEDOT:PSS as the hole‐selecting layer, due to the decreased parasitic absorption of the former. Consequently, 2PACz‐based LBL devices exhibit significantly increased photocurrent, affording a PCE up to 18.2%, which is the highest among the reported A‐D‐A‐type acceptor‐based OSCs. These results deliver important strategies to enhance the performance of OSCs and thus highlight the great potential of M‐series acceptors for practical applications.

A Theoretical Investigation for Exploring the Potential Performance of Non-Fullerene Organic Solar Cells Through Side-Chain Engineering Having Diphenylamino Groups to Enhance Photovoltaic Properties.

The development of ecofriendly fabrication phenomenon is essential requirement for commercialization of non-fullerene acceptors. Recently, end-capped modeling is employed for computational design of five non-fullerene acceptors to elevate various photovoltaic properties. All new molecules are formulated by altering the peripheral acceptors of CH3-2F and DFT methodology is employed to explore the opto-electronic, morphological and charge transfer analysis. From the computational investigation, all reported molecules manifested red shifted absorption with remarkable reduced band gap. Among investigated molecules, FA1-FA3 evinced effectively decreased value of band gaps and designed molecules have low excitation energy justifying proficient charge transference. The lower values of binding energy of FA1 and FA2 suggest their facile exciton dissociation leading to improved charge mobility. By blending with J61 donor, FA4 have sufficiently enhanced value of VOC (1.72eV) and fill factor (0.9228). Energy loss of the model (R) is 0.57eV and statistical calculation demonstrate that all our modified molecules except FA3 has profoundly reduced energy loss compelling in its pivotal utilization. From accessible supportive outcomes of recent investigation, it is recommended that our modified chromophore exhibit remarkable noteworthy applications in solar cells for forthcoming innovations.

The Development of Quinoxaline-Based Electron Acceptors for High Performance Organic Solar Cells.

In the recent advances of organic solar cells (OSCs), quinoxaline (Qx)-based nonfullerene acceptors (QxNFAs) have attracted lots of attention and enabled the recorded power conversion efficiency approaching 20%. As an excellent electron-withdrawing unit, Qx possesses advantages of many modifiable sites, wide absorption range, low reorganization energy, and so on. To develop promising QxNFAs to further enhance the photovoltaic performance of OSCs, it is necessary to systematically summarize the QxNFAs reported so far. In this review, all the focused QxNFAs are classified into five categories as following: SM-Qx, YQx, fused-YQx, giant-YQx, and polymer-Qx according to the molecular skeletons. The molecular design concepts, relationships between the molecular structure and optoelectronic properties, intrinsic mechanisms of device performance are discussed in detail. At the end, the advantages of this kind of materials are summed up, the molecular develop direction is prospected, the challenges faced by QxNFAs are given, and constructive solutions to the existing problems are advised. Overall, this review presents unique viewpoints to conquer the challenge of QxNFAs and thus boost OSCs development further toward commercial applications.

Isomerization Engineering of Solid Additives Enables Highly Efficient Organic Solar Cells via Manipulating Molecular Stacking and Aggregation of Active Layer.

Morphology control is crucial in achieving high-performance organic solar cells (OSCs) and remains a major challenge in the field of OSC. Solid additive is an effective strategy to fine-tune morphology, however, the mechanism underlying isomeric solid additives on blend morphology and OSC performance is still vague and urgently requires further investigation. Herein, two solid additives based on pyridazine or pyrimidine as core units, M1 and M2, are designed and synthesized to explore working mechanism of the isomeric solid additives in OSCs. The smaller steric hindrance and larger dipole moment facilitate better π-π stacking and aggregation in M1-based active layer. The M1-treated all-small-molecule OSCs (ASM OSCs) obtain an impressive efficiency of 17.57%, ranking among the highest values for binary ASM OSCs, with 16.70% for M2-treated counterparts. Moreover, it is imperative to investigate whether the isomerization engineering of solid additives works in state-of-the-art polymer OSCs. M1-treated D18-Cl:PM6:L8-BO-based devices achieve an exceptional efficiency of 19.70% (certified as 19.34%), among the highest values for OSCs. The work provides deep insights into the design of solid additives and clarifies the potential working mechanism for optimizing the morphology and device performance through isomerization engineering of solid additives.

Efficient and Photostable Organic Solar Cells Achieved by Alloyed Dimer Acceptors with Tailored Linker Structures

AbstractHigh power conversion efficiency (PCE) and long‐term stability are prerequisites for commercialization of organic solar cells (OSCs). Herein, two dimer acceptors (DYTVT and DYTCVT) are developed with different properties through linker engineering, and study their effects as alloy‐like acceptors on the photovoltaic performance and photostability of OSCs. These ternary OSCs effectively combine the advantages of both dimer acceptors. DYTVT, characterized by its high backbone planarity, ensures elevated electron mobility and high glass‐transition temperature (Tg), leading to efficient charge transport and enhanced photostability of OSCs. Conversely, DYTCVT, with its significant dipole moment and electrostatic potential, enhances compatibility of the alloy acceptors with donors and refines the blend morphology, facilitating efficient charge generation in OSCs. Consequently, D18:DYTVT:DYTCVT OSCs exhibit higher PCE (18.4%) compared to D18:MYT (monomer acceptor, PCE = 16.5%), D18:DYTVT (PCE = 17.4%), and D18:DYTCVT (PCE = 17.0%) OSCs. Furthermore, owing to higher Tg of alloy acceptors (133 °C) than MYT (Tg = 80 °C) and DYTCVT (Tg = 120 °C), D18:DYTVT:DYTCVT OSCs have significantly higher photostability (t80% lifetime = 4250 h under 1‐sun illumination) compared to D18:MYT (t80% lifetime = 40 h) and D18:DYTCVT OSCs (t80% lifetime = 2910 h).

Simultaneously Improving Stretchability and Efficiency of Flexible Organic Solar Cells by Incorporating a Copolymer Interlayer in Active Layer

AbstractMechanical stretchability is a vital criterion for the wearable application of organic solar cells (OSCs), while the excessive rigidity of fused‐ring small molecular acceptors make the photovoltaic film hard to meet the stretchable requirements. Herein, an effective strategy is developed to construct an intrinsically stretchable active layer by inserting copolymer PM6‐b‐PYSe as an interlayer between layer‐by‐layer processed D18 and BTP‐eC9. The copolymer interlayer shunts the penetration of BTP‐eC9 and facilitates an appropriate phase separation, favoring the enhanced crack onset strain of 17.69% compared to the D18/BTP‐eC9 film (9.67%). Combining with the optimal energy levels, prolonged carrier lifetime, and suppressed bimolecular recombination aroused by the incorporation of PM6‐b‐PYSe, the D18/PM6‐b‐PYSe/BTP‐eC9‐based OSC yields an encouraging efficiency of 17.97%. In particular, the device demonstrates excellent mechanical property, which can retain over 80% after 4000 bending cycles. This work provides an effective strategy to simultaneously enhance the intrinsic mechanical stretchability and photovoltaic performance of flexible OSCs.

Insights Into Preaggregation Control of Y-Series Nonfullerene Acceptors in Liquid State for Highly Efficient Binary Organic Solar Cells.

Leveraging breakthroughs in Y-series nonfullerene acceptors (NFAs), organic solar cells (OSCs) have achieved impressive power conversion efficiencies (PCEs) exceeding 19%. However, progress in advancing OSCs has decelerated due to constraints in realizing the full potential of the Y-series NFAs. Herein, a simple yet effective solid additive-induced preaggregation control method employing 2-chloro-5-iodopyridine (PDCI) is reported to unlock the full potential of the Y-series NFAs. Specifically, PDCI interacts predominantly with Y-series NFAs enabling enhanced and ordered phase-aggregation in solution. This method leads to a notable improvement and a redshifted absorption of the acceptor phase during film formation, along with improved crystallinity. Moreover, the PDCI-induced preaggregation of NFAs in the solution enables ordered molecule packing during the film-formation process through delicate intermediate states transition. Consequently, the PDCI-induced preaggregated significantly improves the PCE of PM6:Y6 OSCs from 16.12% to 18.12%, among the best values reported for PM6:Y6 OSCs. Importantly, this approach is universally applicable to other Y-series NFA-based OSCs, achieving a champion PCE of 19.02% for the PM6:BTP-eC9 system. Thus, the preaggregation control strategy further unlocks the potential of Y-series NFAs, offering a promising avenue for enhancing the photovoltaic performance of Y-series NFA-based OSCs.

N-type small molecule electrolyte cathode interface layer with thickness insensitivity for organic solar cells

Interface engineering has a critical impact on the performances of organic solar cells (OSCs). And cathode interface layer (CIL) with thickness insensitivity is urgently pursued to improve the possibility of industrialization of OSCs. N-type self-doping has been proven effective in increasing electron mobility. Here, four novel n-type small molecule electrolytes (SMEs) with diverse counter anions (CAs), PDIN-BF4, PDIN-BPh4, PDIN-BPhF4, and PDIN-BIm4 were synthesized and employed as cathode interface layers (CILs). Among them, PDIN-BIm4-based OSCs with PM6:Y6 active layer achieved the most glorious electron mobility and thickness insensitivity with a power conversion efficiency (PCE) of 16.98 % due to outstanding self-doping effect and interfacial regulation ability. However, the multi-F atoms on PDIN-BPhF4 may prevent self-doping progress and impede electron transport, thus leading to a low PCE of 11.53 %. Meanwhile, the PDIN-BIm4-based device can maintain over 80 % of the optimal PCE with a thickness of 43 nm or storing in a glove box for 600 h. In addition, PM6: BTP-eC9-based device with PDIN-BIm4 CIL acquired a PCE of 17.82 %, highlighting the broad applicability of PDIN-BIm4. Our work demonstrates that the introduction of CAs into n-type organic materials helps promote the progress of efficient and stable OSCs.

Combined Charge Extraction by Linearly Increasing Voltage and Time-Resolved Microwave Conductivity to Reveal the Dynamic Charge Carrier Mobilities in Thin-Film Organic Solar Cells.

This article reports a purely experiment-based method to evaluate the time-dependent charge carrier mobilities in thin-film organic solar cells (OSCs) using simultaneous charge extraction by linearly increasing the voltage (CELIV) and time-resolved microwave conductivity (TRMC) measurements. This method enables the separate measurement of electron mobility (μe) and hole mobility (μh) in a metal-insulator-semiconductor (MIS) device. A slope-injection-restoration voltage profile for MIS-CELIV is also proposed to accurately determine the charge densities. The dynamic behavior of μe and μh is examined in five bulk heterojunction (BHJ) OSCs of polymer:fullerene (P3HT:PCBM and PffBT4T:PCBM) and polymer:nonfullerene acceptor (PM6:ITIC, PM6:IT4F, and PM6:Y6). While the former exhibits fast decays of μh and μe, the latter, in particular, PM6:IT4F and PM6:Y6, exhibits slow decays. Notably, the high-performing PM6:Y6 demonstrates both a balanced mobility (μe/μh) of 1.0-1.1 within 30 μs and relatively large CELIV-TRMC mobility values among the five BHJs. The results exhibit reasonable consistency with a high fill factor. The proposed new CELIV-TRMC technique offers a path toward a comprehensive understanding of dynamic mobility and its correlation with the OSC performance.

Wide Bandgap Polymer Donors Based on Succinimide-Substituted Thiophene for Nonfullerene Organic Solar Cells.

The advent of nonfullerene acceptors (NFAs) has greatly improved the photovoltaic performance of organic solar cells (OSCs). However, to compete with other solar cell technologies, there is a pressing need for accelerated research and development of improved NFAs as well as their compatible wide bandgap polymer donors. In this study, a novel electron-withdrawing building block, succinimide-substituted thiophene (TS), is utilized for the first time to synthesize three wide bandgap polymer donors: PBDT-TS-C5, PBDT-TSBT-C12, and PBDTF-TSBT-C16. These polymers exhibit complementary bandgaps for efficient sunlight harvesting and suitable frontier energy levels for exciton dissociation when paired with the extensively studied NFA, Y6. Among these donors, PBDTF-TSBT-C16 demonstrates the highest hole mobility and a relatively low highest occupied molecular orbital (HOMO) energy level, attributed to the incorporation of thiophene spacers and electron-withdrawing fluorine substituents. OSC devices based on the blend of PBDTF-TSBT-C16:Y6 achieve the highest power conversion efficiencyof 13.21%, with a short circuit current density (Jsc) of 26.83mA cm-2, an open circuit voltage (Voc) of 0.80V, and a fill factorof 0.62. Notably, the Voc × Jsc product reaches 21.46mW cm-2, demonstrating the potential of TS as an electron acceptor building block for the development of high-performance wide bandgap polymer donors in OSCs.

Control of Multi-Fluorination Number and Position in D-π-A Type Polymers and Their Impact on High-Voltage Organic Photovoltaics.

Exploring the structure-performance relationship of high-voltage organic solar cells (OSCs) is significant for pushing material design and promoting photovoltaic performance. Herein, we chose a D-π-A type polymer composed of 4,8-bis(thiophene-2-yl)-benzo[1,2-b:4,5-b']dithiophene (BDT-T) and benzotriazole (BTA) units as the benchmark to investigate the effect of the fluorination number and position of the polymers on the device performance of the high-voltage OSCs, with a benzotriazole-based small molecule (BTA3) as the acceptor. F00, F20, and F40 are the polymers with progressively increasing F atoms on the D units, while F02, F22, and F42 are the polymers with further attachment of F atoms to the BTA units based on the above three polymers. Fluorination positively affects the molecular planarity, dipole moment, and molecular aggregations. Our results show that VOC increases with the number of fluorine atoms, and fluorination on the D units has a greater effect on VOC than on the A unit. F42 with six fluorine atom substitutions achieves the highest VOC (1.23 V). When four F atoms are located on the D units, the short-circuit current (JSC) and fill factor (FF) plummet, and before that, they remain almost constant. The drop in JSC and FF in F40- and F42-based devices may be attributed to inefficient charge transfer and severe charge recombination. The F22:BTA3 system achieves the highest power conversion efficiency of 9.5% with a VOC of 1.20 V due to the excellent balance between the photovoltaic parameters. Our study provides insights for the future application of fluorination strategies in molecular design for high-voltage organic photovoltaics.

Enhanced and Balanced Carrier Mobility Via n‐Type SnS Dopant Enables High‐Performance Non‐Fullerene Organic Solar Cells

AbstractThe unbalanced electron‐hole mobility is the major bottleneck for boosting the photovoltaic performance of organic solar cells. In this study, 2D n‐type inorganic semiconductor material tin sulfide (SnS) is prepared and introduced into the PM6:Y6 bulk heterojunction organic solar cells to improve photovoltaic performance. The incorporation of SnS promotes Y6 crystallization, and renders the face‐on orientation of Y6 molecules dominant. The improved active layer morphology suppresses carrier recombination and strengthens the electron transport. The electron mobility increases significantly from 4.71 × 10−4 cm2 V−1 s−1 to 7.61 × 10−4 cm2 V−1 s−1 with the hole/electron mobilities (µh/µe) value reducing from 1.67 to 1.11. With enhanced and balanced carrier mobility, the open‐circuit voltage, short‐circuit current density and fill factor of the SnS‐doped PM6:Y6 organic solar cells are improved simultaneously, and the power conversion efficiency is boosted from 16.66 to 18.50%. Additionally, the SnS doped devices exhibit better thermal and storage stability. The improved photovoltaic performance is further verified in PM6:L8‐BO and D18:Y6 based organic solar cells. This work demonstrates that n‐type SnS dopant is an efficient and universal method to improve photovoltaic performance of non‐fullerene organic solar cells.

Highly Efficient and Stable Organic Solar Cells Enabled by a Commercialized Simple Thieno[3,2-b]thiophene Additive.

Delicately manipulating nanomorphology is recognized as a vital and effective approach to enhancing the performance and stability of organic solar cells (OSCs). However, the complete removal of solvent additives with high boiling points is typically necessary to maintain the operational stability of the device. In this study, two commercially available organic intermediates, namely thieno[3,2-b]thiophene (TT) and 3,6-dibromothieno[3,2-b]thiophene (TTB) are introduced, as solid additives in OSCs. The theoretical simulations and experimental results indicate that TT and TTB may exhibit stronger intermolecular interactions with the acceptor Y6 and donor PM6, respectively. This suggests that the solid additives (SAs)can selectively intercalate between Y6 and PM6 molecules, thereby improving the packing order and crystallinity. As a result, the TT-treated PM6:Y6 system exhibits a favorable morphology, improved charge carrier mobility, and minimal charge recombination loss. These characteristics contribute to an impressive efficiency of 17.75%. Furthermore, the system demonstrates exceptional thermal stability (T80>2800h at 65°C) and outstanding photostability. The universal applicability of TT treatment is confirmed in OSCs employing D18:L8-BO, achieving a significantly higher PCE of 18.3%. These findings underscore the importance of using appropriate solid additives to optimize the blend morphology of OSCs, thereby improving photovoltaic performance and thermal stability.

Powerful Role of Benzotriazole Polymers and Small Molecules in Organic Solar Cells.

In the dynamic landscape of renewable energy technologies, organic solar cells (OSCs) have emerged as frontrunners, offering a sustainable and promising alternative for harnessing solar energy. This review article delves into the recent strides made in leveraging the potential of the benzotriazole nucleus within the context of organic solar cells. The unique electronic properties of benzotriazole, coupled with its structural adaptability, position it as a key component in the pursuit of enhancing OSC performance. As researchers delve deeper into the intricacies of this compound, a clearer understanding of its impact on light absorption, charge transport, and overall device stability emerges. The exploration of recent literature in the last three years reveals a rich landscape with innovation and discovery, showcasing the diverse approaches taken to incorporate benzotriazole into different OSC architectures. From fundamental studies elucidating its electronic interactions to applied research refining its integration strategies, the potential of benzotriazole in advancing the capabilities of organic solar cells becomes increasingly evident, and showing that, with the most important advances in the last three years, is the main goal of this article.

Understanding the impact of thiazole unit sequence in π-bridge on the performance of small molecule donor materials

Energy level regulation and crystallization optimization of materials are the key ideas to improve the performance of organic solar cells. In this work, based on clarifying small molecule structure, we introduce thiazole into different positions of π-bridge and investigate its effect on the properties of small molecule donors (SMDs) and related device performance. As thiazole gradually moves towards BDT, the electron clouds of these three SMDs (BTTTzR, BTTzTR and BTzTTR) tend to be divided on the framework, gradually deepened the energy level, and enlarged band gaps. In terms of device performance, the BTTzTR:Y6 device shows good inhibition of charge recombination and phase separation performance, and the efficiency of the related OSCs is 7.87 %. Morphological analysis shows that BTTTzR is prone to form nanoscale microcrystals after thermal annealing treatment, with slightly decreased performance of 6.79 %. BTzTTR is affected by difficult intramolecular charge transfer and weak intermolecular interactions, shows the worst performance of 5.77 %. This work is conducive to a deeper understanding of the electron-deficient substitution of the π-bridge in SMDs.