Inner/Outer Side Chain Engineering of Non-Fullerene Acceptors for Efficient Large-Area Organic Solar Modules Based on Non-Halogenated Solution Processing in Air.

Achieving efficient and large-area organic solar modules via non-halogenated solution processing is vital for the commercialization yet challenging. The primary hurdle is the conservation of the ideal film-formation kinetics and bulk-heterojunction (BHJ) morphology of large-area organic solar cells (OSCs). A cutting-edge non-fullerene acceptor (NFA), Y6, shows efficient power conversion efficiencies (PCEs) when processed with toxic halogenated solvents, but exhibits poor solubility in non-halogenated solvents, resulting in suboptimal morphology. Therefore, in this study, the impact of modifying the inner and outer side-chains of Y6 on OSC performance is investigated. The study reveals that blending a polymer donor, PM6, with one of the modified NFAs, namely N-HD, achieved an impressive PCE of 18.3% on a small-area OSC. This modified NFA displays improved solubility in o-xylene at room temperature, which facilitated the formation of a favorable BHJ morphology. A large-area (55 cm2) sub-module delivered an impressive PCE of 12.2% based on N-HD using o-xylene under ambient conditions. These findings underscore the significant impact of the modified Y6 derivatives on structural arrangements and film processing over a large-area module at room temperature. Consequently, these results are poised to deepen the comprehension of the scaling challenges encountered in OSCs and may contribute to their commercialization.

Colloidal InSb Quantum Dots for 1500 nm SWIR Photodetector with Antioxidation of Surface.

III-V quantum dots (QDs) have emerged as significant alternatives to Cd- and Pb-based QDs, garnering notable attention over the past two decades. However, the understanding of III-V QDs, particularly in the short wave-infrared (SWIR) region, remains limited. InAs QDs are widely recognized as the most prominent SWIR QDs, but their absorption beyond 1400 nm presents various challenges. Consequently, InSb QDs with relatively narrower bandgaps have been investigated; however, research on their device applications is lacking. In this study, InSb QDs are synthesized with absorption ranging from 1000 to 1700 nm by introducing Cl- ions to enhance QD surface stability during synthesis. Additionally, it coated InAs and ZnSe shells onto the InSb QDs to validate photoluminescence in the SWIR region and improve photostability. Subsequently, these QDs are employed in the fabrication of photodetector devices, resulting in photodetection above 1500 nm using Pb-free QDs. The photodetection device exhibited an external quantum efficiency (EQE) of 11.4% at 1370 nm and 6.3% at 1520 nm for InSb core QDs, and 4.6% at 1520 nm for InSb/InAs core/shell QDs, marking the successful implementation of such a device. In detail, the 1520 nm for InSb core device showed a dark current density(JD ) value of: 1.46 × 10-9 A/cm2 , responsivity(R): 0.078 A/W, and specific detectivity based on the shot noise(Dsh *): 3.6 × 1012 Jones at 0 V.

Trifluoromethyl-Substituted Conjugated Random Terpolymers Enable High-Performance Small and Large-Area Organic Solar Cells Using Halogen-Free Solvent.

The advancement of non-fullerene acceptors with crescent-shaped geometry has led to the need for polymer donor improvements. Additionally, there is potential to enhance the photovoltaic parameters in high-efficiency organic solar cells (OSCs). The random copolymerization method is a straightforward and effective strategy to further optimize photoactive morphology and enhance device performance. However, finding a suitable third component in terpolymers remains a crucial challenge. In this study, a series of terpolymer donors (PTF3, PTF5, PTF10, PTF20, and PTF50) is synthesized by introducing varying amounts of the trifluoromethyl-substituted unit (CF3) into the PM6 polymer backbone. Even subtle changes in the CF3 content can significantly enhance all the photovoltaic parameters due to the optimized energy levels, molecular aggregation/miscibility, and bulk-heterojunction morphology of the photoactive materials. Thus, the best binary OSC based on the PTF5:Y6-BO achieves an outstanding power conversion efficiency (PCE) of 18.2% in the unit cell and a PCE of 11.6% in the sub-module device (aperture size: 54.45 cm2 ), when using halogen-free solvent o-xylene. This work showcases the remarkable potential of the easily accessible CF3 unit as a key constituent in the construction of terpolymer donors in high-performance OSCs.

Morphology and Performance Enhancement through the Strong Passivation Effect of Amphoteric Ions in Tin-based Perovskite Solar Cells.

Despite the optoelectronic similarities between tin and lead halide perovskites, the performance of tin-based perovskite solar cells remains far behind, with the highest reported efficiency to date being ≈14%. This is highly correlated to the instability of tin halide perovskite, as well as the rapid crystallization behavior in perovskite film formation. In this work, l-Asparagine as a zwitterion plays a dual role in controlling the nucleation/crystallization process and improving the morphology of perovskite film. Furthermore, tin perovskites with l-Asparagine show more favorable energy-level matching, enhancing the charge extraction and minimizing the charge recombination, leading to an enhanced power conversion efficiency of 13.31% (from 10.54% without l-Asparagine) with remarkable stability. These results are also in good agreement with the density functional theory calculations. This work not only provides a facile and efficient approach to controlling the crystallization and morphology of perovskite film but also offers guidelines for further improved performance of tin-based perovskite electronic devices.

Performance data of CH3NH3PbI3 inverted planar perovskite solar cells via ammonium halide additives.

The data provided in this data set is the study of organic-inorganic hybrid perovskite solar cells fabricated through incorporating the small amounts of ammonium halide NH4X (X = F, Cl, Br, I) additives into a CH3NH3PbI3 (MAPbI3) perovskite solution and is published as "High-Performance CH3NH3PbI3 Inverted Planar Perovskite Solar Cells via Ammonium Halide Additives", available in Journal of Industrial and Engineering Chemistry [1]. A compact and uniform perovskite absorber layer with large perovskite crystalline grains, is realized by simply incorporating small amounts of additives into precursor solutions, and utilizing the anti-solvent engineering technique to control the nucleation and growth of perovskite crystal, turning out the enhanced device efficiency (NH4F: 14.88 ± 0.33%, NH4Cl: 16.63 ± 0.21%, NH4Br: 16.64 ± 0.35%, and NH4I: 17.28 ± 0.15%) compared to that of a reference MAPbI3 device (Ref.: 12.95 ± 0.48%). In addition, this simple technique of ammonium halide addition to precursor solutions increase the device reproducibility as well as long term stability.

Synthesis of ITIC Derivatives with Extended π-Conjugation as Non-Fullerene Acceptors for Organic Solar Cells.

The realization of printed organic solar cells (OSCs) as a commercial technology is dependent on the development of high-performance photovoltaic materials suitable for large-scale device manufacture. In this study, the design, synthesis, and characterization of a series of A-D-A'-D-A-type molecular acceptors based on indacenodithienothiophene (IDTT) and thiophene-flanked 2,1,3-benzothiadiazole (DTBT) are reported. The synthesized molecular acceptors showed broader absorption ranges and narrower band gap energies than those of well-known 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)-based molecular acceptors. Furthermore, the synthesized acceptors could tune the frontier molecular orbital energy levels, dipole moments, and their crystallinities by introducing fluorine (F) atoms and cyano (CN) groups on DTBT as a core A' unit. The cyano-substituted DTBT-based molecular acceptor (CNDTBT-IDTT-FINCN) showed a strong molar absorptivity and dipole moment, high hole/electron charge mobilities, and a favorable face-on orientation using films blended with 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). An inverted organic photovoltaic (OPV) device using CNDTBT-IDTT-FINCN exhibits a power conversion efficiency (PCE) of 9.13% when using PBDB-T as a donor material in small cells (0.12 cm2). Sub-module devices with an active area of 55.45 cm2 are fabricated using bar-coating and exhibit PCEs of up to 7.50%. This demonstration of a high-efficiency large-area device makes CNDTBT-IDTT-FINCN a suitable and promising candidate for printed OPV devices.

Simple and Versatile Non-Fullerene Acceptor Based on Benzothiadiazole and Rhodanine for Organic Solar Cells.

Most non-fullerene acceptors (NFAs) are designed in a complex planar molecular conformation containing fused aromatic rings in high-efficiency organic solar cells (OSCs). To obtain the final molecules, however, numerous synthetic steps are necessary. In this work, a novel simple-structured NFA containing alkoxy-substituted benzothiadiazole and a rhodanine end group (BTDT2R) is designed and synthesized. We also investigate the photovoltaic properties of BTDT2R-based OSCs employing representative polymer donors (wide band gap and high-crystalline P3HT, medium band gap and semicrystalline PPDT2FBT, and narrow band gap and low-crystalline PTB7-Th) to compare the performance capabilities of fullerene acceptor-based OSCs, which are well matched with various polymer donors. OSCs based on P3HT:BTDT2R, PPDT2FBT:BTDT2R, and PTB7-Th:BTDT2R achieved efficiency as high as 5.09, 6.90, and 8.19%, respectively. Importantly, photoactive films incorporating different forms of optical and molecular ordering characteristics exhibit favorable morphologies by means of solvent vapor annealing. This work suggests that the new n-type organic semiconductor developed here is highly promising as a universal NFA that can be paired with various polymer donors with different optical and crystalline properties.

Amine-Based Interfacial Engineering in Solution-Processed Organic and Perovskite Solar Cells.

Solution-processed organic solar cells (OSCs) and hybrid perovskite solar cells (PvSCs) generally require appropriate transparent electrode with a low work function, which improves the electron extraction, increases the built-in potential, and suppresses charge recombinations. Hence, interfacial modifiers between the cathode and the photoactive layer play a significant role in OSCs and PvSCs, as they provide suitable energy-level alignment, leading to desirable charge carrier selectivity and suppressing charge carrier recombinations at the interfaces. Here, we present a comprehensive study of the energy-level mapping between a transparent electrode and photoactive layers to enhance the electron-transport ability by introducing amine-based interfacial modifiers (ABIMs). Among the ABIMs, polyethylenimine ethoxylated (PEIE) incorporating inverted OSCs shows enhanced power conversion efficiencies (PCEs) from 0.32 to 9.83% due to large interfacial dipole moments, leading to a well-aligned energy level between the cathode and the photoactive layer. Furthermore, we explore the versatility of the PEIE ABIM by employing different photoactive layers with fullerene derivatives, a nonfullerene acceptor, and a perovskite layer. Promisingly, inverted nonfullerene OSCs and planar n-i-p PvSCs with PEIE ABIM show outstanding PCEs of 11.88 and 17.15%, respectively.

Stable P3HT: amorphous non-fullerene solar cells with a high open-circuit voltage of 1 V and efficiency of 4.

A non-fullerene small molecule acceptor, SF-HR composed of 3D-shaped spirobifluorene and hexyl rhodanine, was synthesized for use in bulk heterojunction organic solar cells (OSCs). It possesses harmonious molecular aggregation between the donor and acceptor, due to the interesting diagonal molecular shape of SF-HR. Furthermore, the energy level of SF-HR matches well with that of the donor polymer, poly(3-hexyl thiophene) (P3HT) in this system which can affect efficient charge transfer and transport properties. As a result, OSCs made from a P3HT:SF-HR photoactive layer exhibited a power conversion efficiency rate of 4.01% with a high V OC of 1.00 V, a J SC value of 8.23 mA cm-2, and a FF value of 49%. Moreover, the P3HT:SF-HR film showed superior thermal and photo-stability to P3HT:PC71BM. These results indicate that SF-HR is specialized as a non-fullerene acceptor for use in high-performance OSCs.

High-Efficiency Nonfullerene Polymer Solar Cells with Band gap and Absorption Tunable Donor/Acceptor Random Copolymers.

Energy level alignment between a donor and an acceptor has a critical role in determining the open-circuit voltage ( VOC) in polymer solar cells (PSCs). Also, broad absorption of the photoactive layer is required to generate a high photocurrent. Herein, non-fullerene PSCs with D/A random copolymers and 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) has been demonstrated. The D/A random copolymers are composed of a 2-ethylhexylthienyl-substituted benzo[1,2- b:4,5- b']dithiophene (BDT) donor unit (D) and a fluorinated thieno[3,4- b]thiophene (TT-F) acceptor unit (A). By controlling the D/A unit ratio in the polymer backbone, it is possible to modulate both the energy levels and absorption spectra of random copolymers. As the ratio of the donor unit in the polymer back bone increases, the highest occupied molecular orbital energy level is located deeper, leading to higher VOC. Also, the absorption spectra of random copolymers become blue-shifted with an increase of the donor unit ratio; it compensates the weak absorption region of ITIC. This complementary absorption enhances the photocurrent, leading to higher power conversion efficiency (PCE). Because of the optimization of the D/A ratio of random copolymers, a notable PCE of 10.27% can be achieved in PSCs with D5A and ITIC.

Effective Molecular Engineering Approach for Employing a Halogen-Free Solvent for the Fabrication of Solution-Processed Small-Molecule Solar Cells.

To utilize the potential of small-molecule-based organic solar cells, proper designs of the photoactive materials which result in reasonable performance in a halogen-free solvent system and thickness tolerance over a range are required. One of the best approaches to achieve these requirements is via the molecular engineering of small-molecule electron donors. Here, we have modified a previously reported dithienobenzodithiophene (DTBDT)-based small molecule (SM1) via the dimerization approach, that is, the insertion of an additional DTBDT into the main backbone of the small molecule (SM2). An SM1-based photoactive film showed severe pinhole formation throughout the film when processed with a halogen-free o-xylene solvent. On the other hand, the modified small-molecule SM2 formed an excellent pinhole-free film when processed with the o-xylene solvent. Because of the dimerization of the DTBDT in the SM2 core, highly crystalline films with compact lamellae and an enhanced donor/acceptor interdigitation were formed, and all of these factors led to a high efficiency of 8.64% with chloroform and 8.37% with the o-xylene solvent systems. To the best of our knowledge, this study represents one of the best results with the SM donor and fullerene derivative acceptor materials that have shown the device performance with halogen-free solvents.

High-Performance CH3NH3PbI3-Inverted Planar Perovskite Solar Cells with Fill Factor Over 83% via Excess Organic/Inorganic Halide.

The reduction of charge carrier recombination and intrinsic defect density in organic-inorganic halide perovskite absorber materials is a prerequisite to achieving high-performance perovskite solar cells with good efficiency and stability. Here, we fabricated inverted planar perovskite solar cells by incorporation of a small amount of excess organic/inorganic halide (methylammonium iodide (CH3NH3I; MAI), formamidinium iodide (CH(NH2)2I; FAI), and cesium iodide (CsI)) in CH3NH3PbI3 perovskite film. Larger crystalline grains and enhanced crystallinity in CH3NH3PbI3 perovskite films with excess organic/inorganic halide reduce the charge carrier recombination and defect density, leading to enhanced device efficiency (MAI+: 14.49 ± 0.30%, FAI+: 16.22 ± 0.38% and CsI+: 17.52 ± 0.56%) compared to the efficiency of a control MAPbI3 device (MAI: 12.63 ± 0.64%) and device stability. Especially, the incorporation of a small amount of excess CsI in MAPbI3 perovskite film leads to a highly reproducible fill factor of over 83%, increased open-circuit voltage (from 0.946 to 1.042 V), and short-circuit current density (from 18.43 to 20.89 mA/cm2).

Two-dimensional TiO2 honeycomb structure for enhanced light extraction from polymer light-emitting diodes.

We have demonstrated the preparation of an ordered hole pattern via a simple colloidal assembly technique and a sol-gel process without the use of any special equipment to enhance light extraction from polymer light-emitting diodes (LEDs). From two-dimensional (2D) polystyrene (PS) colloidal crystals, 2D TiO2 honeycomb structures were easily obtained after depositing TiO(x) sol solution onto the colloidal crystals by a doctor blade technique and removing the PS colloidal particles. In order to optimize the thickness of the deposited TiO(x) materials for fabricating 2D TiO2 honeycomb structures, the concentration of the TiO(x) sol solution was controlled. By applying the 2D TiO2 honeycomb structure on the backside of the glass substrate, the efficiency of a polymer LED, compared to the device without the structure, was increased without a significant change in the electroluminescence spectrum. This enhancement is attributed to the improved light extraction, which is due to the suppression of total internal reflection at the interface between the glass substrate and the air.

Dye-sensitized solar cells with Pt- and TCO-free counter electrodes.

Here for the first time, we demonstrate novel DSSCs with a Pt- and TCO-free counter electrode, which have a highly conductive polymer exhibiting high catalytic ability and charge transport, and the photovoltaic performance increases as we increase the PEDOT film conductivity.