Materials For Organic Solar Cells Research Articles

Graphene oxide-titanium oxide-polyaniline hybrid materials for high-performance dye-sensitized solar cells

A new solar cell that comprises a graphene oxide and titanium oxide nanoparticle (NP) composite with graphitized polyaniline (PANI) has been tested in polymer solar cells (PSCs). In this study, a series of conjugated polymers were synthesized and evaluated as the absorber and hole-transport layer materials in organic solar cells, demonstrating the significant impact of the chemical structure of the polymers on solar cell performance. The incorporation of graphene oxide (GOX) and titanium oxide TiO2 NP in conjugated polymers, particularly when graphitized within the PANI layer, led to improved open-circuit voltages compared to structurally similar polymers without NP. The morphology of the composite films was analyzed and related to the photovoltaic performance of polymers synthesized with polyaniline PANI-base and PANI-salt. Optimal NP addition in PANI-salt, PANI-base, PANI-base-TiO2, and PANI-base-GOX resulted in open-circuit voltages and efficiencies of 433 mV and 3.67%, 250 mV and 0.595%, 310 mV and 1.358%, and 520 mV and 2.366%, respectively. This study underscores the importance of polymer film uniformity in the performance of PSCs, with the highest efficiency obtained using a conjugated polymer with the best PANI-salt and PANI-base-GOX films. The research sheds light on the relationship between polymer structure and device photovoltaic performance, which is crucial for the design of new polymeric materials for efficient use and stable OSCs and PSCs.

Enhancing predictive modeling of photovoltaic materials’ solar power conversion efficiency using explainable AI

We present a study on Explainable AI-based prediction of power conversion efficiency (PCE) of organic solar cells, conducted on a dataset of 566 small-molecule organic solar cell materials samples with varying donor and acceptor species combinations. This research uncovers an interesting phenomenon, the first of its kind to be reported, of PCE quantization, where the PCE values increase in steps with the increase in feature values. Our findings have significant implications for the development of efficient organic solar cells, as they provide a better understanding of the factors that influence PCE, and highlight the feature value ranges for which more efficient PCE would be achieved. Our study demonstrates the power of XAI techniques in uncovering hidden patterns in scientific datasets and highlights the importance of interdisciplinary research in the field of materials science.

Single‐Layer Carbon Nitride as an Efficient Metal‐Free Organic Electron‐Transport Material with a Tunable Work Function

AbstractSingle‐layer carbon nitride (SLCN) is introduced as a metal‐free organic electron transport material (ETL) for organic solar cells, delivering a performance comparable to that of the benchmark nanocrystalline ZnO. SLCN is produced in the form of stable aqueous inks and can serve as an efficient electron transport layer for three different types of active layers, showing high stability to photodegradation. A lower conductivity of SLCN films as compared to ZnO is counter‐balanced by their higher transparency and lower light scattering losses. The SLCN ETL provides a unique opportunity to tune the work function from ca. −4.1 to −4.6 eV by varying the annealing temperature due to partial thermal oxidation of the SLCN film. The PL band position follows the oxidation‐induced changes of the work function allowing PL properties of SLCN to be used to predict the PV efficiency. The 2D structure of SLCN coupled with unique structural and compositional variability, and tunability of the work function show a high promise for emerging organic PV devices.

Triselenasumanene-based organic molecules as donor and hole-transporting materials for next-generation solar cells

The optoelectronic and charge transport properties of triselenasumanene-based organic molecules were studied using electronic structure calculations to explore their potential as a hole-transporting material (HTM) in perovskite solar cells (PSCs) and as electron donors in organic solar cells (OSCs). Based on the recently synthesized triselenasumanene (SESUM) molecule, nine molecules (SESUMXn, where X = anthracene (A), tetracene (T) and pentacene (P), n = number of attached A, T and P, i.e. 1, 2 and 3) were designed by extending the π-conjugation. The newly designed molecules possessed suitable energy-level alignment with the energy bands of commonly used perovskite material, CH3NH3PbI3, in PSCs, and are suitable as electron-donor material with the commonly used acceptor material, PC61BM, in OSCs. The calculated ionic state properties and electrophilicity index also showed that the studied molecules were potential donor materials for OSCs. Further, the calculated open circuit voltage and fill factor of SESUM and anthracene- and tetracene-substituted SESUM molecules were comparable with those of recently reported donor molecules. The calculated absorption spectra, effective hole transfer integral and stacking angle distribution showed the suitability of SESUMX2 and SESUMX3 molecules as HTM in PSCs. The results of periodic density functional theory calculations showed that the tri-substituted SESUM molecules, SESUMX3 (where, X = A, T and P), were effectively adsorbed on the CH3NH3PbI3 surface and abstracted the hole carrier from the perovskite surface.

The impact of ester groups on 1,8-naphthalimide electron transport material in organic solar cells

Recently, 1,8-naphthalimide (NI) molecules have emerged as a new category of organic electron transport materials (ETMs) employed in organic solar cells (OSCs). Among them, NI molecules with a "NI-π-NI" molecular structure commonly exhibit over aggregation in films owing to their planar molecular structures, which is unfavorable for solution-processed film fabrication in OSC devices. In this work, we successfully synthesized a new NI molecule named NDT-2, employing a strategy that incorporates a solubilizing ester group modification to induce twisted molecular planarity, thereby reducing intermolecular over-aggregation and optimizing quality of the film. Interestingly, the NDT-2 modified by ester groups as a π bridge exhibits an enlarged molecular dihedral angle, enhanced alcohol solubility, a smoother film surface morphology, and improved film forming quality. Ultimately, OSCs incorporating NDT-2 as the ETM achieved a notable power conversion efficiency (PCE) of 17.1%. This study introduces a design strategy that utilizes ester functional groups to improve film forming quality of ETM, offering valuable insights for the development of advanced, alcohol-soluble NI molecules as efficient ETMs in OSCs.

Hybrid Organic-Inorganic ZnO/PCBM Electron Transport Layer with Organic Lead Halide Perovskite Solar Cell Materials CH3NH3PbIX2, X is Cl or I

An experimental investigation has been undertaken to explore a variety of properties of organic perovskite solar cells (OPSCs) that are distinct in their photovoltaic response. In this study, OPSCs were constructed using zinc oxide, ZnO and [6,6]-phenylC[Formula: see text]-acid methyl ester, PCBM, as electron transfer materials (ETM), poly(3-hexylthiophene), P3HT, as hole transport material (HTM), and CH3NH3PbIX2 as a photosensitizer, where X is either Cl or I. The structural and optical characteristics of the ETM and HTM layers and the perovskite materials of OPSCs were investigated. The [Formula: see text]–[Formula: see text] and [Formula: see text]–[Formula: see text] curves of each solar cell prepared in OPSCs were measured using an integrated cell tester. This comprises a photovoltaic [Formula: see text]–[Formula: see text] measurement system and a solar simulation system. As a result of these results, the OPSC’s performance is evaluated. The calculations in this work suggest that the highest power conversion efficiency (PCE = 6.31%) was achieved in photovoltaic devices using CH3NH3PbI3 as the effective absorber layer and ZnO with PCBM as the ETM layer. At a light intensity of 100 mW/cm2, each OPSC cell was performed. Under the same conditions, the [Formula: see text]–[Formula: see text] curves were evaluated for each OPSC device. By improving the selection of organic and inorganic active materials in the ETM layer, OPSC performance may be improved.

Development of fullerene acceptors and the application of non-fullerene acceptors in organic solar cells

Organic solar cells (OSCs) enjoy a huge market and public attention as an emerging renewable and clean energy source due to their accessibility, sustainability, translucency, good flexibility, non-toxicity, and low preparation cost. However, the choice of an acceptor material is now the pivotal factor restricting the development of OSCs. To continuously improve stability and increase power conversion efficiency (PCE) for better performance, high-performance acceptor materials are an important part of enabling OSCs. From fullerenes and their derivatives and non-fullerenes, we sum up the latest research progress on high-performance acceptor materials for OSCs and then introduce the synthesis methods of non-fullerenes. The latest strategies to enhance the performance of organic solar cells and the wide range of applications of non-fullerene acceptors (NFAs) on different OSCs are also discussed. In addition, challenges faced by OSCs in improving their performance and the prospects for future development are revealed, providing new ideas for designing the next generation of high-performance OSCs.

Rational molecular engineering towards efficient heterojunction solar cells based on organic molecular acceptors

The selection of photoactive layer materials for organic solar cells (OSCs) is essential for the photoelectric conversion process. It is well known that chlorophyll is an abundant pigment in nature and is extremely valuable for photosynthesis. However, there is little research on how to improve the efficiency of chlorophyll-based OSCs by matching chlorophyll derivatives with excellent non-fullerene acceptors to form heterojunctions. Therefore in this study we utilize a chlorophyll derivative, Ce6Me3, as a donor material and investigate the performance of its heterojunction with acceptor materials. Through density functional theory, the photoelectric performances of acceptors, including the fullerene derivative PC71BM and the terminal halogenated non-fullerene DTBCIC series, are compared in detail. It is found that DTBCIC-Cl has better planarity, light absorption, electron affinity, charge reorganization energy and charge mobility than others. Ce6Me3 has good energy level matching and absorption spectral complementarity with the investigated acceptor molecules and also shows good electron donor properties. Furthermore, the designed Ce6Me3/DTBCIC interfaces have improved charge separation and reorganization rates (K CS/K CR) compared with the Ce6Me3/PC71BM interface. This research provides a theoretical basis for the design of photoactive layer materials for chlorophyll-based OSCs.

Chemical similarity-based design of materials for organic solar cells: Visualizing the generated chemical space of polymers

Potential candidates for photovoltaic applications can be found using chemical similarity analysis. Compounds with similar structural characteristics may perform similarly. Designing of materials for organic solar cells (OSCs) is a difficult and time-consuming process. An existing polymer database is mined to find polymers for OSCs, three polymers (PM6, PBT7-Th, and D18) are used as standard. However, good polymers are not found from this database. A large database of polymers is generated using an automatic method that is implemented on RDkit. Synthetic accessibility of generated polymers is calculated. Similarity analysis is conducted to search the polymers from the generated database. Similarity analysis is performed using Tanimoto index. Large number of potential candidates for polymer solar cells are found. Structure Activity Landscape Index (SALI) plot is used to quantitatively characterize activity landscapes.

Tunning interfacial interaction strategy by asymmetric configuration to construct self-assembly materials for efficient organic solar cells

Developing highly ordered self-assembled monolayer is very critical and challenging for realizing high-performance organic solar cells. Herein, we develop an asymmetric carbazole derived molecule 1Cl-PACz by the introduction of single Cl atom to modulate energy level alignment and induce densely assembly. 1Cl-PACz exhibits an improved molecular dipole moment, thus modulating the work function of indium tin oxide (ITO) electrodes to facilitate charge extraction. Moreover, 1Cl-PACz is proven to have strengthened π-π interaction observed in its single crystal, forming densely assembly on the substrates. Excitingly, a champion power conversion efficiency of 19.0 % can be obtained when 1Cl-PACz is evaluated as hole-extraction channel, among the highest values for the SAMs derived cells to date. This study opens new avenues for exploring high-performance SAMs materials to boost the performance of OSC devices.

A Scalable and Chromatography‐Free Synthesis of N,N‐Bis(9,9‐dimethyl‐9H‐fluoren‐2‐yl)‐3′,3′,4′,7′‐tetramethyl‐2′,3′‐dihydrospiro[fluorene‐9,1′‐indene]‐2‐amine, a new Hole Transport Material for Organic Solar Cells

AbstractThe title triarylamine N,N‐bis(9,9‐dimethyl‐9H‐fluoren‐2‐yl)‐3′,3′,4′,7′‐tetramethyl‐2′,3′‐dihydrospiro[fluorene‐9,1′‐indene]‐2‐amine is a new hole transport material for organic solar cells. After investigating different discovery approaches (Schemes 1 + 2), a multi gram‐scale synthetic sequence was developed (Scheme 4). The key intermediate 2‐bromo‐9‐(2,5‐dimethylphenyl)‐9H‐fluorene was accessible from 2‐bromo‐9‐fluorenone by either the sequence Grignard reaction, Et3SiH/BF3 reduction or by direct arylation of the corresponding 2‐bromo‐9‐fluorenol. Alkylation at C(9) of 2‐bromo‐9‐(2,5‐dimethylphenyl)‐9H‐fluorene with methallyl chloride and cyclization by an intramolecular Friedel‐Crafts alkylation led to the key building block 2‐bromo‐3′,3′,4′,7′‐tetramethyl‐2′,3′‐dihydrospiro[fluorene‐9,1′‐indene] (Scheme 4). A Buchwald‐Hartwig coupling was employed (Scheme 3 + 4) for the assembly of the final triarylamines. The developed gram‐scale synthesis of the title compound is scalable and chromatography‐free with an overall yield >25 % over 5 steps.

A Three-Dimensional Non-Fullerene Acceptor with Contorted Hexabenzocoronene and Perylenediimide for Organic Solar Cells.

Although fullerene derivatives such as [6,6]-phenyl-C61/C71-butyric acid methyl ester (PC61BM/PC71BM) have dominated the the photoactive acceptor materials in bulk heterojunction organic solar cells (OSCs) for decades, they have several drawbacks such as weak absorption, limited structural tunability, prone to aggregation, and high costs of production. Constructing non-fullerene small molecules with three-dimensional (3D) molecular geometry is one of the strategies to replace fullerenes in OSCs. In this study, a 3D molecule, contorted hexa-cata-hexabenzocoronene tetra perylenediimide (HBC-4-PDI), was designed and synthesized. HBC-4-PDI shows a wide and strong light absorption in the whole UV-vis region as well as suitable energy levels as an acceptor for OSCs. More importantly, the 3D construction effectively reduced the self-aggregation of c-HBC, leading to an appropriate scale phase separation of the blend film morphology in OSCs. A preliminary power conversion efficiency of 2.70 % with a champion open-circuit voltage of 1.06 V was obtained in OSCs with HBC-4-PDI as the acceptor, which was the highest among the previously reported OSCs based on c-HBC derivatives. The results indicated that HBC-4-PDI may serve as a good non-fullerene acceptor for OSCs.

Propeller-shaped NI isomers of cathode interfacial material for efficient organic solar cells

Propeller-shaped NI isomers of cathode interfacial material for efficient organic solar cells

Graphene and Graphene Derived Nanomaterials as Versatile Candidates for Organic Solar Cells and Smart Windows Applications – A Review

AbstractGraphene and related materials have been employed in several applications till date due to the unique set of properties. Research in the area of organic solar cells and smart windows are important to meet the increasing global energy demands and to realize the future goal of zero energy buildings. Here, we present a summary of the important research progress in application of graphene and related materials in organic solar cells and smart windows. This review starts by introducing the need of photovoltaic technology including organic solar cells and smart windows. The remaining sections are broadly divided into two sections – the first one briefly introduces organic cells and their different types, and the next section focuses on the different chromogenic technologies used in smart windows. After a brief overview of graphene, the application of graphene and related materials in organic cells and smart windows are presented. In the end, some of the major challenges and possible research directions are also outlined. Hopefully, this review will shed light on the recent trends and directions to achieve enhancement in performance of organic solar cells and smart windows with integration of graphene and provide overview for researchers about this novel field.

Understanding photochemical degradation mechanisms in photoactive layer materials for organic solar cells.

Over the past decades, the field of organic solar cells (OSCs) has witnessed a significant evolution in materials chemistry, which has resulted in a remarkable enhancement of device performance, achieving efficiencies of over 19%. The photoactive layer materials in OSCs play a crucial role in light absorption, charge generation, transport and stability. To facilitate the scale-up of OSCs, it is imperative to address the photostability of these electron acceptor and donor materials, as their photochemical degradation process remains a challenge during the photo-to-electric conversion. In this review, we present an overview of the development of electron acceptor and donor materials, emphasizing the crucial aspects of their chemical stability behavior that are linked to the photostability of OSCs. Throughout each section, we highlight the photochemical degradation pathways for electron acceptor and donor materials, and their link to device degradation. We also discuss the existing interdisciplinary challenges and obstacles that impede the development of photostable materials. Finally, we offer insights into strategies aimed at enhancing photochemical stability and discuss future directions for developing photostable photo-active layers, facilitating the commercialization of OSCs.

Conjugated backbone optimization of an all-fused-ring acceptor for efficient and stable organic solar cells.

Three all-fused-ring acceptors with different conjugated backbone are designed as acceptor materials for organic solar cells. It is found that the horizontally extended conjugation of all-fused-ring acceptors leads to better photovoltaic performance compared to the vertically extended analogue. The results provide a guideline for designing high-performance and stable all-fused-ring acceptor materials.

Ternary polythiophene enables over 17% efficiency organic solar cells

Two ternary polythiophenes (PTs), PT-CN and PT-2CN, as donors are developed to deepen energy levels, reduce miscibility and regulate crystallinity. PT-CN:BTP-eC9 based OSCs gain an impressive PCE of 17.27%, which is the record for PT-based OSCs.

Additive-assisted strategy for high-efficiency organic solar cells

Herein, we summarize the recent advances of the additive-assisted strategy with solvent/solid additives and binary additives and their working mechanism in OSCs.

Flexible, transparent, and sustainable cellulose-based films for organic solar cell substrates.

Cellulose, often considered a highly promising substitute for petroleum-based plastics, offers several compelling advantages, including abundant availability, cost-effectiveness, environmental friendliness, and biodegradability. However, its inherent highly crystalline structure and extensive hydrogen-bonded network pose challenges for processing and recycling. In this study, we introduce the concept of cellulose vitrimers (CVs), wherein dynamic bonds are incorporated to reconfigure the hydrogen-bonded network, resulting in a mechanically robust, highly transparent material. CVs exhibit exceptional malleability, thermal stability, and noteworthy resistance to water and solvents. Due to the dynamic bond disassociation, CVs can be effectively chemically recycled using a well-established "dissolution-and-reforming" process. Moreover, CVs have proven successful as flexible substrate materials for organic solar cells, outperforming traditional petroleum-based polyethylene naphthalate (PEN). Given these advantages, CVs have the potential to replace conventional petroleum-based materials as recyclable and environmentally friendly alternatives, particularly within the realm of electronic devices and displays.

Accelerating the generation and discovery of high-performance donor materials for organic solar cells by deep learning

A deep learning-based framework (DeepDonor) has been developed to find high-performance donor materials. The experimental PCEs of devices based on two discovered candidates were 16.27% and 15.07%.