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Polymer Films for Photovoltaic Applications II

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A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Membranes and Films".

Deadline for manuscript submissions: closed (1 February 2024) | Viewed by 23779

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Prof. Dr. Bożena Jarząbek

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Center of Polymer and Carbon Materials of the Polish Academy of Sciences, 41-819 Zabrze, Poland
Interests: organic materials and conjugated polymers; thin films and nanotechnology; materials characterization; optical spectroscopy; absorption edge parameters; electronic transitions; thermo-optical properties; doping; polymer films in optoelectronic structures
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Dear Colleagues,

This Special Issue focuses on polymer thin films and polymer blend films in photovoltaic (PV) structures. Organic materials are widely used in optoelectronic devices (e.g., organic solar cells (OSCs)), mainly due to the low cost of production (thin films may be deposited at low temperature on a large surface, on flexible substrates). However, polymer compounds in OSC systems also have certain limitations, such as low efficiency and short lifetime of devices, resulting from an insufficient thermal and time stability. Polymers, which may be utilized in PV systems, should exhibit the appropriate optical properties (e.g., a wide range of absorption and low energy gap), good durability and stability (not undergoing any phase transitions or degradation in the temperature range in which the system is working), and relevant electronic structure (good alignment of molecular orbitals of donor and acceptor compounds in bulk heterojunction (BHJ) organic solar cells).

This Special Issue covers all fields related to polymer films for photovoltaic applications, but special attention will be given to the following aspects:

Synthesis and suitable modification of polymer structure, to obtain polymer thin films for PV devices;
Influence of film deposition (thermal vacuum evaporation (TVE), chemical vapor deposition (CVD), spin coating, spray, etc.) on the properties of polymer films;
Thermo-optical properties of polymer thin films and blends of polymer films, as potential parts of PV systems;
Influence of doping or protonation of polymer thin films and blend polymer films on their properties;
Polymer thin films as active layers in PV solar cells—correlation of chemical structure and PV properties;
BHJ solar cells with polymer blends films—the choice of blend film composition to obtain the best PV parameters.

Authors are welcome to submit their latest research in the form of original full articles, communications, or reviews on this topic.

Prof. Dr. Bożena Jarząbek
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

polymer thin films
polymer blends films
doped polymer films
thermo-optical properties
organic solar cells
BHJ photovoltaic structures

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Published Papers (10 papers)

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Research

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13 pages, 2707 KiB

Open AccessArticle

Highly Efficient Flexible Roll-to-Roll Organic Photovoltaics Based on Non-Fullerene Acceptors

by Yu-Ching Huang, Hou-Chin Cha, Shih-Han Huang, Chia-Feng Li, Svette Reina Merden Santiago and Cheng-Si Tsao

Polymers 2023, 15(19), 4005; https://doi.org/10.3390/polym15194005 - 6 Oct 2023

Cited by 4 | Viewed by 1873

Abstract

The ability of organic photovoltaics (OPVs) to be deposited on flexible substrates by roll-to-roll (R2R) processes is highly attractive for rapid mass production. Many research teams have demonstrated the great potential of flexible OPVs. However, the fabrication of R2R-coated OPVs is quite limited. There is still a performance gap between the R2R flexible OPVs and the rigid OPVs. In this study, we demonstrate the promising photovoltaic characteristics of flexible OPVs fabricated from blends of low bandgap polymer poly[(2,6-(4,8-bis(5-(2-ethylhexyl)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)] (PBDB-T) and non-fullerene 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC). We successfully R2R slot-die coated the flexible OPVs with high power conversion efficiency (PCE) of over 8.9% under irradiation of simulated sunlight. Our results indicate that the processing parameters significantly affect the PCE of R2R flexible OPVs. By adjusting the amount of solvent additive and processing temperature, as well as optimizing thermal annealing conditions, the high PCE of R2R slot-die coated OPVs can be obtained. These results provide significant insights into the fundamentals of highly efficient OPVs for the R2R slot-die coating process. Full article

(This article belongs to the Special Issue Polymer Films for Photovoltaic Applications II)

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16 pages, 2464 KiB

Open AccessArticle

Optimization and Efficiency Enhancement of Modified Polymer Solar Cells

by Muhammad Raheel Khan and Bożena Jarząbek

Polymers 2023, 15(18), 3674; https://doi.org/10.3390/polym15183674 - 6 Sep 2023

Cited by 3 | Viewed by 1998

Abstract

In this study, an organic bulk heterojunction (BHJ) solar cell with a spiro OMeTAD as a hole transport layer (HTL) and a PDINO as an electron transport layer (ETL) was simulated through the one-dimensional solar capacitance simulator (SCAPS-1D) software to examine the performance of this type of organic polymer thin-film solar cell. As an active layer, a blend of polymer donor PBDB-T and non-fullerene acceptor ITIC-OE was used. Numerical simulation was performed by varying the thickness of the HTL and the active layer. Firstly, the HTL layer thickness was optimized to 50 nm; after that, the active-layer thickness was varied up to 80 nm. The results of these simulations demonstrated that the HTL thickness has rather little impact on efficiency while the active-layer thickness improves efficiency significantly. The temperature effect on the performance of the solar cells was considered by simulations performed for temperatures from 300 to 400 K; the efficiency of the solar cell decreased with increasing temperature. Generally, polymer films are usually full of traps and defects; the density of the defect (N_t) value was also introduced to the simulation, and it was confirmed that with the increase in defect density (N_t), the efficiency of the solar cell decreases. After thickness, temperature and defect density optimization, a reflective coating was also applied to the cell. It turned out that by introducing the reflective coating to the back side of the solar cell, the efficiency increased by 2.5%. Additionally, the positive effects of HTL and ETL doping on the efficiency of this type of solar cells were demonstrated. Full article

(This article belongs to the Special Issue Polymer Films for Photovoltaic Applications II)

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13 pages, 3498 KiB

Open AccessArticle

All-Polymer Solar Cells Sequentially Solution Processed from Hydrocarbon Solvent with a Thick Active Layer

by Yajie Wang, Chaoyue Zhao, Ziqi Cai, Lihong Wang, Liangxiang Zhu, Hui Huang, Guoping Zhang, Peng You, Chen Xie, Yaping Wang, Qing Bai, Tao Yang, Shunpu Li and Guangye Zhang

Polymers 2023, 15(16), 3462; https://doi.org/10.3390/polym15163462 - 18 Aug 2023

Cited by 1 | Viewed by 1643

Abstract

Organic solar cells (OSCs) have gained increasing attention. Among the various directions in OSCs, all-polymer solar cells (all-PSCs) have emerged as a highly promising and currently active research area due to their excellent film formation properties, mechanical properties, and thermal stabilities. However, most of the high-efficiency all-PSCs are processed from chloroform with an active layer thickness of ~100 nm. In order to meet the requirements for industrialization, a thicker active layer processed from low-vapor pressure solvents (preferentially a hydrocarbon solvent) is strongly desired. Herein, we employ toluene (a hydrocarbon solvent with a much higher boiling point than chloroform) and a method known as sequential processing (SqP) to mitigate the rapid decline in efficiency with increasing film thickness. We show that SqP enables a more favorable vertical phase segregation that leads to less trap-assisted recombination and enhanced charge extraction and lifetime than blend-cast devices at higher film thicknesses. Full article

(This article belongs to the Special Issue Polymer Films for Photovoltaic Applications II)

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18 pages, 4293 KiB

Open AccessArticle

Preparation and Interfacial Properties of Hydroxyl-Containing Polyimide Fibers

by Jiang Du, Chuanzhi Pu, Xianyu Sun, Qi Wang, Hongqing Niu and Dezhen Wu

Polymers 2023, 15(4), 1032; https://doi.org/10.3390/polym15041032 - 19 Feb 2023

Cited by 4 | Viewed by 2288

Abstract

Developing polyimide (PI) fibers with excellent interfacial adhesion and high mechanical properties for the PI fiber-reinforced polymer matrix composites (PFRPs) industry has been challenging. In this work, 4,4′-diamino-(1,1′-biphenyl)-3,3′-diol (HAB) diamine was introduced into the rigid molecular chains, and the high-performance PI fibers, presenting an interfacial shear strength (IFSS) value of 46.33 MPa, tensile strength of 2.62 GPa, and modulus of 100.15 GPa, were successfully manufactured when the content of HAB in mixed diamines was 30 mol %. Fourier transform infrared (FTIR) spectroscopy identified the presence of intermolecular H-bonding interactions, and 2D small-angle X-ray scattering indicated that the introduction of HAB moiety contributed to reducing the radii of microvoids in the fibers, which were considered to be the key factors leading to a significant enhancement in the mechanical properties of the fibers. X-ray photoelectron spectroscopy (XPS) and the static contact angle intuitively illustrated that the synthetic fiber surface contained active hydroxyl groups. The IFSS value of PI fiber/epoxy resin composites (PI/EPs) was 56.47 MPa when the content of HAB reached 70 mol %. Failure morphologies confirmed that the interfacial adhesion of PI/EPs was enhanced owing to the surface activity of PI fibers. Consequently, this study provides an effective strategy to the long-standing problems of high mechanical performances and poor surface activity for traditional PI fibers used in the PFRPs industry. Full article

(This article belongs to the Special Issue Polymer Films for Photovoltaic Applications II)

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18 pages, 5294 KiB

Open AccessArticle

Molecular Weight-Dependent Oxidation and Optoelectronic Properties of Defect-Free Macrocyclic Poly(3-hexylthiophene)

by Ryohei Sato, Atsuo Utagawa, Koji Fushimi, Feng Li, Takuya Isono, Kenji Tajima, Toshifumi Satoh, Shin-ichiro Sato, Hiroshi Hirata, Yoshihiro Kikkawa and Takuya Yamamoto

Polymers 2023, 15(3), 666; https://doi.org/10.3390/polym15030666 - 28 Jan 2023

Cited by 1 | Viewed by 2389

Abstract

The redox behaviors of macrocyclic molecules with an entirely π-conjugated system are of interest due to their unique optical, electronic, and magnetic properties. In this study, defect-free cyclic P3HT with a degree of polymerization (DP_n) from 14 to 43 was synthesized based on our previously established method, and its unique redox behaviors arising from the cyclic topology were investigated. Cyclic voltammetry (CV) showed that the HOMO level of cyclic P3HT decreases from –4.86 eV (14 mer) to –4.89 eV (43 mer), in contrast to the linear counterparts increasing from –4.94 eV (14 mer) to –4.91 eV (43 mer). During the CV measurement, linear P3HT suffered from electro-oxidation at the chain ends, while cyclic P3HT was stable. ESR and UV–Vis–NIR spectroscopy suggested that cyclic P3HT has stronger dicationic properties due to the interactions between the polarons. On the other hand, linear P3HT showed characteristics of polaron pairs with multiple isolated polarons. Moreover, the dicationic properties of cyclic P3HT were more pronounced for the smaller macrocycles. Full article

(This article belongs to the Special Issue Polymer Films for Photovoltaic Applications II)

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18 pages, 5505 KiB

Open AccessArticle

Investigation of the Conditions for the Synthesis of Poly(3,4-ethylenedioxythiophene) ATRP Macroinitiator

by Marin Božičević, Lucija Fiket, Magdalena Vujasinović, Roko Blažic, Marin Kovačić and Zvonimir Katančić

Polymers 2023, 15(2), 253; https://doi.org/10.3390/polym15020253 - 4 Jan 2023

Cited by 2 | Viewed by 1744

Abstract

One of the most widely used conductive polymers in the growing conductive polymer industry is poly(3,4-ethylenedioxythiophene) (PEDOT), whose main advantages are good thermal and chemical stability, a conjugated backbone, and ease of functionalization. The main drawback of PEDOT for use as wearable electronics is the lack of stretchable and self-healing properties. This can be overcome by grafting PEDOT with flexible side branches. As pure PEDOT is highly stable and grafting would not be possible, a new bromine-functionalized thiophene derivative, 2-(tiophen-3-yl) ethyl 2-bromo-2-methylpropanoate (ThBr), was synthesized and copolymerized with EDOT for the synthesis of a poly(EDOT-co-ThBr) ATRP macroinitiator. After the synthesis of the macroinitiator, flexible polymers could be introduced as side branches by atom-transfer radical polymerization (ATRP) to modify mechanical properties. Before this last synthesis step, the conditions for the synthesis of the ATRP macroinitiator should be investigated, as only functionalized units can function as grafting sites. In this study, nine new copolymers with different monomer ratios were synthesized to investigate the reactivity of each monomer. The ratios used in the different syntheses were ThBr:EDOT = 1:0.2, 1:0.4, 1:0.6, 1:0.8, 1:1, 0.8:1, 0.6:1, 0.4:1, and 0.2:1. In order to determine the effect of reaction time on the final properties of the polymer, macroinitiator synthesis at a 1:1 ratio was carried out at different time periods: 8 h, 16 h, 24 h, and 48 h. The obtained products were characterized by different techniques, and it was found that polymerizations longer than 24 h yielded practically insoluble macroinitiators, thus limiting its further application. Reactivity ratios of both monomers were found to be similar and close to 1, making the copolymerization reaction symmetrical and the obtained macroinitiators almost random copolymers. Full article

(This article belongs to the Special Issue Polymer Films for Photovoltaic Applications II)

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14 pages, 1906 KiB

Open AccessFeature PaperArticle

PEDOT:PSS Conductivity Enhancement through Addition of the Surfactant Tween 80

by Joseph L. Carter, Catherine A. Kelly, Jean E. Marshall, Vicki Hammond, Vannessa Goodship and Mike J. Jenkins

Polymers 2022, 14(23), 5072; https://doi.org/10.3390/polym14235072 - 22 Nov 2022

Cited by 7 | Viewed by 3177

Abstract

Replacement of indium tin oxide with the intrinsically conducting polymer poly(3,4–ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been of significant interest in recent years as a result of lower processing and material costs. In addition, the inclusion of additives has been reported to further enhance the conductivity, rheology, and wettability of PEDOT:PSS. In this study, Tween 80 was shown to decrease the sheet resistance of PEDOT:PSS films from approximately 1000 to 76 Ω□⁻¹ at a 2.67 wt% surfactant concentration. Through X-ray diffraction, Raman spectroscopy, and atomic force microscopy, it was shown that the surfactant caused phase separation and structural ordering of the PEDOT and PSS components, leading to this improvement in conductivity. Furthermore, Tween 80 altered the rheological properties and decreased the surface tension of PEDOT:PSS, making coating common commodity polymers, often used as flexible substrates, more viable. Full article

(This article belongs to the Special Issue Polymer Films for Photovoltaic Applications II)

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14 pages, 3453 KiB

Open AccessArticle

Fabrication and Characterization of Hybrid Hole Transporting Layers of Organotin (IV) Semiconductors within Molybdenum Oxide/Poly(3,4-ethylenedyoxithiophene) Polystyrene Sulfonate Matrices

by María Elena Sánchez Vergara, César Raúl Monzón González, José Ramón Álvarez Bada, Leon Hamui and Cecilio Álvarez Toledano

Polymers 2022, 14(19), 4143; https://doi.org/10.3390/polym14194143 - 3 Oct 2022

Cited by 1 | Viewed by 1819

Abstract

The hybrid film of molybdenum oxide (MoO₃) and poly(3,4-ethylenedyoxithiophene) polystyrene sulfonate (PEDOT:PSS) is a promising candidate for use as hole transport layer (HTL) in low-cost devices. A fast, controllable and economic process was used to fabricate high-performance HTLs by adding organotin (IV) semiconductors to the MoO₃/PEDOT:PSS films. These hybrid films were fabricated by spin-coating and the MoO₃/PEDOT:PSS-organotin (IV) complex films were characterized by infrared spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Some mechanical and optical properties of the hybrid films were obtained and, to electrically characterize the hybrid films, hetero-junction glass/ITO/MoO₃/PEDOT:PSS-organotin (IV) complex/Ag devices were prepared. Regarding the mechanical properties, the films have high plastic deformation, with a maximum stress of around 40 MPa and a Knoop hardness of 0.14. With respect to optical behavior, the films showed high transparency, with optical gap values between 2.8 and 3.5 eV and an onset gap of around 2.4 eV, typical of semiconductors. Additionally, the films in their respective devices show ambipolar and ohmic behavior with small differences depending on the substituent in organotin (IV) semiconductors. The MoO₃/PEDOT:PSS matrix defines the mechanical behavior of the films and the tin complexes contribute their optoelectronic properties. Full article

(This article belongs to the Special Issue Polymer Films for Photovoltaic Applications II)

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14 pages, 4962 KiB

Open AccessArticle

Structural, Thermal, and Electrical Properties of Poly(Ethylene Oxide)—Tetramethyl Succinonitrile Blend for Redox Mediators

by Ravindra Kumar Gupta, Hamid Shaikh, Ahamad Imran, Idriss Bedja and Abdullah Saleh Aldwayyan

Polymers 2022, 14(18), 3728; https://doi.org/10.3390/polym14183728 - 7 Sep 2022

Cited by 2 | Viewed by 1930

Abstract

An all-solid–state dye-sensitized solar cell is one of the non-fossil fuel-based electrochemical devices for electricity generation in a high-temperature region. This device utilizes a redox mediator, which is a fast ion-conducting solid polymer electrolyte (SPE). The SPE makes the device economical, thinner, and safer in high-temperature regions. The SPE generally has a form of matrix−plasticizer−redox salts. Succinonitrile (SN) is generally employed as a plasticizer for reducing the crystallinity of poly(ethylene oxide), abbreviated as PEO, a common polymeric matrix. In the present paper, the structural and thermal properties of tetramethyl succinonitrile (TMSN) were compared with SN for its application as a solid plasticizer. TMSN and SN both are plastic crystals. TMSN has four methyl groups by replacing the hydrogen of the SN, resulting in higher molecular weight, solid–solid phase transition temperature, and melting temperature. We thoroughly studied the structural, thermal, and electrical properties of the [(1−x)PEO: xTMSN] blend for utilizing it as a matrix, where x = 0–0.25 in mole fraction. The FT-IR spectra and XRD patterns of the blends exhibited PEO-alike up to x = 0.15 mole and TMSN-alike for x > 0.15 mole. Differential scanning calorimetry revealed formation of a eutectic phase from x = 0.1 mole and phase separation from x = 0.15 mole. The blends with x = 0.1–0.15 mole had a low value of PEO crystallinity. Thermogravimetric analysis showed thermal stability of the blends up to 75 °C. The blends exhibited electrical conductivity, σ_25°C more than 10⁻⁹ S cm⁻¹, and Arrhenius behavior (activation energy, ~0.8 eV) in a temperature region, 25–50 °C. Full article

(This article belongs to the Special Issue Polymer Films for Photovoltaic Applications II)

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Review

Jump to: Research

29 pages, 11342 KiB

Open AccessReview

Crystallization of D-A Conjugated Polymers: A Review of Recent Research

by Yibo Hu, Xinxiu Cao and Hui Fan

Polymers 2022, 14(21), 4612; https://doi.org/10.3390/polym14214612 - 30 Oct 2022

Cited by 7 | Viewed by 3394

Abstract

D-A conjugated polymers are key materials for organic solar cells and organic thin-film transistors, and their film structure is one of the most important factors in determining device performance. The formation of film structure largely depends on the crystallization process, but the crystallization of D-A conjugated polymers is not well understood. In this review, we attempted to achieve a clearer understanding of the crystallization of D-A conjugated polymers. We first summarized the features of D-A conjugated polymers, which can affect their crystallization process. Then, the crystallization process of D-A conjugated polymers was discussed, including the possible chain conformations in the solution as well as the nucleation and growth processes. After that, the crystal structure of D-A conjugated polymers, including the molecular orientation and polymorphism, was reviewed. We proposed that the nucleation process and the orientation of the nuclei on the substrate are critical for the crystal structure. Finally, we summarized the possible crystal morphologies of D-A conjugated polymers and explained their formation process in terms of nucleation and growth processes. This review provides fundamental knowledge on how to manipulate the crystallization process of D-A conjugated polymers to regulate their film structure. Full article

(This article belongs to the Special Issue Polymer Films for Photovoltaic Applications II)

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