Lowest Unoccupied Molecular Orbital Levels Research Articles

Side chain-engineered pseudocapacitive semiconducting polymer electrodes for symmetrical supercapacitors operable at wide potentials

Pseudocapacitive electrodes based on inorganic metal oxides exhibit superior capacitance. However, they suffer from limited operational voltage, resulting in low energy and power densities. To address these issues, redox semiconducting polymer (SP)-based pseudocapacitive electrodes, integrating electron donor and acceptor functionalities, offer a promising solution. In this study, we introduce two novel pseudocapacitive SP electrodes composed of highly planar electron-donating building blocks 4,8-bis ((5-octylthiophen-2-yl)ethynyl)benzo[1,2-b:4,5-b'] dithiophene (TBDT) with an electron-accepting building blocks benzo[c][1,2,5]thiadiazole (BT) and its side chain manipulated counterpart, i.e., OBT, denoted as SP1 and SP2, respectively. Among them, SP2 demonstrates a maximum specific capacitance of 117 F/g at 1 A/g. Furthermore, a symmetric supercapacitor fabricated for full-cell applications exhibits a significant energy density, reaching 29.1 Wh kg−1, and a maximum power density of 12.4 kW kg−1 within the wide operating potential window of 2.5 V. The exceptional performance of the pseudocapacitive electrode can be attributed to its highly planar backbone, nanoporous morphology, low crystallinity, and low lowest unoccupied molecular orbital levels. Overall, this new class of pseudocapacitive polymer electrode holds great potential for diverse sustainable energy storage technologies, addressing the limitations of traditional inorganic metal oxide-based electrodes by offering wide potentials window.

Unexpected Electronic Features of NiO Quantum Dots Produced by Femtosecond Pulsed Laser Ablation in Water.

This study examines the effect of quantum confinement and surface orientations on the electronic properties of NiO quantum dots. It compares NiO nanocrystals produced via atmospheric-pressure microplasma and femtosecond laser (fs-laser) ablation in water, finding that both methods yield quantum-confined nanocrystals with a defined face-centered cubic lattice. Notably, fs-laser synthesis generates crystalline nanocrystals from both crystalline and amorphous targets. While the electronic properties, i.e., energy of the highest occupied molecular orbital and lowest unoccupied molecular orbital (LUMO), of microplasma-synthesized NiO nanocrystals are consistent with the literature, the electronic characteristics of NiO nanocrystals produced by a fs-laser, particularly the high-lying LUMO level, are unusual for NiO quantum dots. Supported by density functional theory calculations, we show that the observed level positions are related to the different polar and nonpolar faces of the nanocrystal surface.

Surfactant Composition Dependent Evolution of Electronic/Structural Properties of P3HT Nanoparticle Colloids Synthesized via Mini-Emulsion Technique

: This study investigates the influence of surfactant (sodium dodecyl sulfate, SDS) concentration on the size and optoelectronic properties of poly(3-hexylthiophene) (P3HT) nanoparticles (NPs) synthesized via the mini-emulsion technique. P3HT NPs were fabricated with varying SDS concentrations. The size dependent optoelectronic properties, including the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels, were analyzed through photoelectron spectroscopy in air, UV-Vis absorption spectroscopy and cyclic voltammetry. A clear trend of decreasing NP size with increasing SDS concentration was observed. Higher SDS levels resulted in smaller NPs with enhanced pi-pi stacking and shorter conjugation lengths. This structural change led to a noticeable shift in HOMO and LUMO levels, indicating a direct correlation between surfactant concentration and the electronic properties of the P3HT NPs. The absorption spectra revealed a decrease in the A0-0/A0-1 ratio with smaller NP size, suggesting a transition towards more pronounced H-aggregate characteristics. As the size of the P3HT NPs decreases, there is a notable increase in H-aggregate formation. This increase can be attributed to enhanced interchain interactions between the polymer chains. In smaller NPs, the surface area-to-volume ratio is higher, leading to more significant interactions between adjacent polymer chains. These interactions promote the formation of H-aggregates, characterized by their interchain pi-pi stacking, which differs from the intrachain coupling observed in J-aggregates.

Photocatalytic activity in graded off-valent cations substituted NaNbO3

This study investigates the impact of off-valent doping on the photocatalytic properties of NaNbO3 concerning the degradation of Methylene Blue. Compositions with x values of 0.00 (representing pure NaNbO3, denoted as NBO) and 0.05 within the material system Na1-xAxNbO3 (where A is K1+, Ba2+, La3+, abbreviated as K-NBO, Ba-NBO, and La-NBO respectively) were synthesized using the conventional solid-state reaction method. The UV–visible analysis revealed a decrease in the band gap for samples K-NBO and Ba-NBO, while an increase was observed for sample La-NBO. Raman modes of lower wave numbers merged and shifted towards the higher wave number side. The determination of valence band edge and conduction band edge involved computational analysis based on XPS survey scans, and the band gap energy values were derived from UV–Visible spectroscopy results. Examining the band diagram of the samples (NBO, K-NBO, Ba-NBO, and La-NBO) in conjunction with the highest occupied molecular orbital and lowest unoccupied molecular orbital levels of MB dye provided insights into potential degradation mechanisms. Photocatalytic dye degradation experiments for Methylene Blue demonstrated that doping increased the degradation efficiency of samples K-NBO, Ba-NBO, and La-NBO compared to NBO. Among all NaNbO3 based prepared samples, Ba-NBO exhibited the highest degradation efficiency of 96%, however slightly less than the reference sample P25 TiO2.

Bis(benzoselenadiazol)ethane: A π‐Extended Acceptor‐Dimeric Unit for Ambipolar Polymer Transistors with Hole and Electron Mobilities Exceeding 10 cm2 V−1 s−1

AbstractThe lack of ambipolar polymers with balanced hole (μh) and electron mobilities (μe) >10 cm2 V−1 s−1 is the main bottleneck for developing organic integrated circuits. Herein, we show the design and synthesis of a π‐extended selenium‐containing acceptor‐dimeric unit, namely benzo[c][1,2,5]selenadiazol‐4‐yl)ethane (BBSeE), to address this dilemma. In comparison to its sulfur‐counterpart, BBSeE demonstrates enlarged co‐planarity, selective noncovalent interactions, polarized Se−N bond, and higher electron affinity. The successful stannylation of BBSeE offers a great opportunity to access acceptor‐acceptor copolymer pN‐BBSeE, which shows a narrower band gap, lower‐lying lowest unoccupied molecular orbital level (−4.05 eV), and a higher degree of backbone planarity. Consequently, the pN‐BBSeE‐based organic transistors display an ideally balanced ambipolar transporting property with μh and μe of 10.65 and 10.72 cm2 V−1 s−1, respectively. To the best of our knowledge, the simultaneous μh/μe values >10.0 cm2 V−1 s−1 are the best performances ever reported for ambipolar polymers. In addition, pN‐BBSeE shows an excellent shelf‐storage stability, retaining over 85 % of the initial mobility values after two months storage. Our study demonstrates the π‐extended acceptor‐dimeric BBSeE is a promising acceptor building block for constructing high‐performance ambipolar polymers applied in next‐generation organic integrated circuit.

Bis(benzoselenadiazol)ethane: A π-Extended Acceptor-Dimeric Unit for Ambipolar Polymer Transistors with Hole and Electron Mobilities Exceeding 10 cm2 V-1 s-1.

The lack of ambipolar polymers with balanced hole (μh) and electron mobilities (μe) >10 cm2 V-1 s-1 is the main bottleneck for developing organic integrated circuits. Herein, we show the design and synthesis of a π-extended selenium-containing acceptor-dimeric unit, namely benzo[c][1,2,5]selenadiazol-4-yl)ethane (BBSeE), to address this dilemma. In comparison to its sulfur-counterpart, BBSeE demonstrates enlarged co-planarity, selective noncovalent interactions, polarized Se-N bond, and higher electron affinity. The successful stannylation of BBSeE offers a great opportunity to access acceptor-acceptor copolymer pN-BBSeE, which shows a narrower band gap, lower-lying lowest unoccupied molecular orbital level (-4.05 eV), and a higher degree of backbone planarity. Consequently, the pN-BBSeE-based organic transistors display an ideally balanced ambipolar transporting property with μh and μe of 10.65 and 10.72 cm2 V-1 s-1, respectively. To the best of our knowledge, the simultaneous μh/μe values >10.0 cm2 V-1 s-1 are the best performances ever reported for ambipolar polymers. In addition, pN-BBSeE shows an excellent shelf-storage stability, retaining over 85 % of the initial mobility values after two months storage. Our study demonstrates the π-extended acceptor-dimeric BBSeE is a promising acceptor building block for constructing high-performance ambipolar polymers applied in next-generation organic integrated circuit.

Bifunctional Urea–Polyethyleneimine‐Mediated Surface Engineering in SnO2 Electron‐Transport Layer for Efficient and Stable Organic Solar Cells

Because of its high conductivity, wide bandgap, and excellent photostability, tin oxide (SnO2) has long been recognized as an electron‐transport layer (ETL) in organic solar cells (OSCs). However, the energy‐level mismatch between the work function (WF) of SnO2 and the lowest unoccupied molecular orbital level of Y‐series nonfullerene acceptors (NFAs), along with the abundance of surface defects on SnO2, have limited its widespread application as ETLs in OSCs. Herein, a novel approach utilizing urea‐functionalized polyethyleneimine (PEI) materials called u‐PEIs for modifying SnO2 is introduced. This modification, which serves dual purposes of WF modulation and surface‐defect passivation, can mitigate the energy barriers of SnO2/Y‐series NFA and increase the conductivity of the SnO2 film. PM6:Y6‐based OSCs with u‐PEI‐modified SnO2 (SnO2:u‐PEI) ETLs exhibit a remarkable efficiency of 16%, which significantly exceeds that (13.5%) achieved with bare SnO2‐based OSCs, along with outstanding photo‐ and thermal stability. This study confirms the efficacy of urea‐functionalized PEI for efficient and stable OCSs, paving the way for SnO2 applications.

Design of Chlorinated Indaceno[1,2-b:5,6-b']dithiophene Acceptors toward Efficient Organic Photovoltaics.

Chlorinated modifications have been extensively employed to modulate the optoelectronic properties of π-conjugated materials. Herein, the Cl substitution in designing nonfullerene acceptors (NFAs) with various bandgaps is studied. Four narrow-bandgap electron acceptors (GS-40, GS-41, GS-42, and GS-43) were synthesized by tuning the electrostatic potential distributions of the molecular conjugated backbones. The optical absorption onset of these NFAs ranges from 900 to 1030 nm. Compared to the nonchlorinated analogue, the introduction of Cl atoms on the core of indaceno[1,2-b:5,6-b'] dithiophene (IDT) and π spacer results in an upward shift of the lowest unoccupied molecular orbital levels and induces a blue shift in the absorption spectra of the NFAs. This alteration facilitates achieving appropriate energy-level alignment and favorable bulk heterojunction morphology when blended with the widely used donor PBDB-TF. The PBDB-TF:GS-43-based solar cells show an optimal power conversion efficiency of 13.3%. This work suggests the potential of employing chlorine-modified IDT and thiophene units as fundamental building blocks for developing high-performance photoactive materials.

Improved Capacitive Energy Storage at High Temperature via Constructing Physical Cross‐Link and Electron–Hole Pairs Based on P‐Type Semiconductive Polymer Filler

AbstractIn this work, p‐type polymer semiconductor poly(2‐((3,6,7,10,11‐pentakis (hexyloxy) triphenylene‐2‐yl)oxy)ethyl methacrylate) (PMHT) is added into polyetherimide (PEI). Benefiting from the electrostatic interaction between strong electrophilic charged phenyls of the PEI matrix and strong electronegative benzophenanthrene unit of the PMHT filler, the physical cross‐linked networks are formed in polymer blends. Meanwhile, the lowest unoccupied molecular orbital level of PEI is close to the highest occupied molecular orbital level of PMHT, which is easy to establish electron–hole pair by Coulomb force. Thus, the carrier trap is constructed in the heterojunction region between PMHT filler and PEI matrix. Both physically cross‐linked networks and electron–hole pairs can promote breakdown strength (Eb) of PEI and decrease energy loss. Importantly, PMHT filler can improve the dielectric constant of PEI. As a result, 0.75 wt% PMHT/PEI delivers an ultrahigh discharge energy density (Ud) of 10.7 J cm−3 at an Eb of 680 MV m−1 and at room temperature, and maintains a charge and discharge efficiency of above 90%. In addition, a superior Ud of 5.1 and 3.3 J cm−3 is achieved at 150 and 200 °C, respectively. This paper creates a new perspective for preparing high‐properties polymer dielectrics by combining the advantages of cross‐linking and electron–hole pairs.

Lifetime enhancement in QDLEDs via an electron-blocking hole transport layer

This study investigates the impact of an engineered hole transport layer (HTL) on the stability of electroluminescent quantum dot light-emitting devices (QDLEDs). The 9-Phenyl-3,6-bis(9-phenyl-9Hcarbazol-3-yl)-9H-carbazole (Tris-PCz) HTL, which possesses a shallower lowest unoccupied molecular orbital (LUMO) energy level compared to the widely used 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) HTL, is employed to confine electron overflow toward the HTL. Utilizing the Tris-PCz HTL results in a 20× improvement in the electroluminescence half-life (LT50) of QDLEDs compared with conventional QDLEDs using the CBP HTL. Electric and optoelectronic analyses reveal that the migration of excess electrons toward the HTL is impeded by the up-shifted LUMO level of Tris-PCz, contributing to prolonged operational device stability. Furthermore, the augmented electric field at the QD/Tris-PCz interface, due to accumulated electrons, expedites hole injection rates, leading to better charge injection balance and the confinement of the exciton recombination zone within the QD and thus the device stability enhancement. This study highlights the significant influence of the HTL on QDLED stability and represents one of the longest LT50 for a QDLED based on the conventional core/shell QD structure.

Effect of fluorine substitution on the electronic states and conductance of CuPc on Cu(100)

The electronic states and conductance of CuPc, F8CuPc, and F16CuPc on Cu(100) were studied by using scanning tunneling microscopy (STM) and the density functional theory (DFT) calculations. For all molecules, the lowest unoccupied molecular orbital (LUMO) was observed around the Fermi level (EF), regardless of the difference in the original LUMO levels of the free molecules. This indicates that the strong interaction causes the pinning of EF at LUMO levels. Meanwhile, the differential conductance at EF is drastically affected by the substitution: it increases and decreases for CuPc and F16CuPc, respectively, suggesting that the Fano effect plays a major role in the conductance. This finding provides a new strategy for the control of molecular conductance by chemical substitution.

Sequential Cyanation of Polythiophenes: Tuning Charge Carrier Polarity in Organic Electrochemical Transistors

AbstractPolythiophenes, built on head‐to‐head (HH) linked 3,3′‐oligomer ethylene glycol‐2,2′‐bithiophene (gT2), have simple chemical structure, good backbone planarity, and relatively high‐lying the lowest unoccupied molecular orbital (LUMO) energy levels, hence showing excellent p‐type performance in organic electrochemical transistors (OECTs) with µC* of several hundred F cm−1 V−1 s−1. In this study, sequential cyano substitution is utilized to enable transformation of charge carrier polarity from p‐type to n‐type in OECTs, based on the parent polythiophene g4T2‐T2. With the increase of cyano group number, the polythiophenes exhibit gradually lowered LUMO levels from −2.55 to −3.90 eV. As a result, from g4T2‐T2 to CNg4T2‐CNT2, the p‐type performance dramatically diminishes accomplished by the enhancement of n‐type one when applied in OECTs. To the authors' delight, polymer CNg4T2‐CNT2 with the highest content of cyano groups exhibits a remarkable n‐type µC* of 27.01 F cm−1 V−1 s−1 and high gm,norm of 6.75 S cm−1 with negligible p‐type character. This study demonstrates that sequential cyano substitution provides a powerful approach for developing high‐performance n‐type polymers for OECT applications.

Manipulating cation-water chemistry to inhibit hydrogen evolution of zinc metal anodes

The electrochemical behavior of zinc metal anodes is dominated by the interfacial chemistry between the anode and the electrolyte. The local enrichment of cation-solvent complexes with strong interactions in the Helmholtz plane can lead to the evolution of hydrogen on the Zn anode surface during cycling. To tackle this issue, we propose the addition of low doses of N-dimethylformamide (DMF) solvent into 2 M of ZnSO4 electrolyte (D-ZS) to inhibit hydrogen evolution from water splitting and dendrite growth. Molecular dynamics simulation and nuclear magnetic resonance spectroscopy reveal that high donor-number DMF molecules replace part of H2O molecules, thereby reducing the amount of H2O in the solvated sheath of Zn2+. Furthermore, density functional theory calculations demonstrate that DMF increases the lowest unoccupied molecular orbital level of bound water owing to reduced Zn2+ cation-water interaction, preventing the breakage of O−H bond and reducing side reactions of Zn anodes. In addition, the desolvated DMF molecules prefer to adsorb on the zinc anode surface, hindering the migration of Zn2+ to low surface-energy positions that could lead to dendritic formation. As a result, a symmetric cell with D-ZS electrolyte can operate for over 1970 h at 0.5 mA cm−2 for 0.25 mAh cm−2, and Zn-ion hybrid supercapacitors achieve an exemplary cycle performance (93% of capacity retention rate after 30,000 cycles at 2 A g−11). The present work provides a roadmap for regulating electrolyte structure to inhibit hydrogen evolution of zinc metal anodes by manipulating Zn2+ cation-water chemistry.

D-A-D type small molecule donors based on BODIPY skeleton for bulk heterojunction organic solar cells

In recent years, structural modification for boron-dipyrromethene (BODIPY) derivatives has been proven to be an effective way to improve their performance of organic solar cells (OSCs). Here, three D-A-D type small molecule donors BDP-1, BDP-2 and BDP-3 were synthesized based on 3,5,8-trimethyl BODIPY dye as the core by the introduction of 4-(diethylamino)phenyl, 4-diethylamino-2-methoxyphenyl and 4-(diphenylamino)phenyl at the 3, 5 and 8 positions, respectively, and used for the construction of organic solar cells. BDP-1, BDP-2, and BDP-3 are synthesized. Due to the strong electron-donating ability of the substituted groups at 3, 5, and 8 positions of BODIPY core, three donors exhibit extended π-conjugation and effective intramolecular charge transfer, resulting in the strong absorption in the range of 500–––900 nm with narrow band gaps below 1.52 eV. BDP-1, BDP-2 and BDP-3 display complementary absorption spectra and suitable highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital levels (LUMO) with fullerene derivative PC71BM. These molecules (BDP-1, BDP-2 or BDP-3) as electron donor were applied into BHJ solar cells by using PC71BM as electron acceptor. The performance of BHJ organic solar cells is systematically investigated and compared. The optimized solar cells based on BDP-1, BDP-2 and BDP-3 show high power conversion efficiencies (PCEs) of 9.52%, 11.83% and 5.27%, respectively. The OSCs based on BDP-2: PC71BM exhibited excellent short-circuit current density (Jsc), high electron mobility and open-circuit voltage (Voc). This work demonstrates that BODIPY derivatives with simple-structured show great potential for high performance OSCs.

Fine‐Tuning Alkyl Chains on Quinoxaline Nonfullerene Acceptors Enables High‐Efficiency Ternary Organic Solar Cells with Optimizing Molecular Stacking and Reducing Energy Loss

AbstractMaterial design of guest acceptor is always a big challenge for improving the efficiency of ternary organic solar cells (OSCs). Here, a pair of isomeric nonfullerene acceptors based on quinoxaline core, Qx–p‐C7H8O and Qx–m‐C7H8O, is designed and synthesized. By moving the alkoxy chain attached on side phenyl from meta‐position to para‐position, both π–π stacking distance and crystallinity are enhanced simultaneously. They obtain the uplifted lowest unoccupied molecular orbital level. Compared to Qx–m‐C7H8O, Qx–p‐C7H8O exhibits wider absorption spectrum and higher extinction coefficient. Using D18‐Cl:N3 as host materials, the addition of guest acceptor Qx–p‐C7H8O significantly improves the power conversion efficiency (PCE) from 17.61% to 18.49% because of higher open‐circuit voltage (0.875 V) and short‐circuit current density (27.85 mA cm−2). This can be attributed to the faster exciton dissociation, more balanced carrier mobility, fine fiber morphology, and lower energy loss in the ternary devices. However, Qx–m‐C7H8O‐based ternary device achieves relatively low PCE of 17.17% because this device shows extremely low electron mobility. The results indicate that molecular stacking, film morphology, etc., can be effectively modulated by fine‐tuning the side chains of guest materials, which may be an effective design rule for further improving the PCE of OSCs.

Role of cations in the photovoltaic performance optimization of ternary stannates, MSnO3 (M = Ca, Sr, and Ba) and N2SnO4 (N = Ca, Sr, Ba, and Zn)

Given the tremendous interest in next-generation photoelectric conversion devices, such as tandem solar cells, indoor photoelectric conversion devices, and image sensors, the development of device-specific electron transport materials is essential for achieving high performance. Sn-based semiconductors are one of the edge materials with the potential to satisfy these requirements. In particular, ternary stannate compounds have shown high potential as electron transport electrodes in several impressive studies. However, systematic research on the electronic band structure and chemical bonding characteristics of these materials remains insufficient. In this study, we present the effect of cations on the crystal structure and electronic band structure of ternary stannate compounds, MSnO3 (MSO, M = Ca, Sr, and Ba) and N2SnO4 (N2SO, N = Ca, Sr, Ba, and Zn). Additionally, their potential as electron transport electrodes is verified by application in dye-sensitized solar cells (DSCs). Notably, although BaSnO3 (BSO) and Zn2SnO4 (Z2SO) had inferior dye adsorption properties, they exhibited higher overall performance in DSCs than the other stannate compounds. The origin of the excellent performances of BSO and Z2SO is attributed to their supportive electronic band features, including the lower flat-band potential and conduction band than that of the lowest unoccupied molecular orbital level of N719 dye and excellent charge transport property. This study highlights the decisive impact of the electronic band structure and charge transport ability of stannate compounds on the photoelectric conversion performance and provides design guidelines for developing new charge transport materials.

Effects of HAT-CN Layer Thickness on Molecular Orientation and Energy-Level Alignment with ZnPc.

Efficient energy-level alignment is crucial for achieving high performance in organic electronic devices. Because the electronic structure of an organic semiconductor is significantly influenced by its molecular orientation, comprehensively understanding the molecular orientation and electronic structure of the organic layer is essential. In this study, we investigated the interface between a 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) hole injection layer and a zinc-phthalocyanine (ZnPc) p-type organic semiconductor. To determine the energy-level alignment and molecular orientation, we conducted in situ ultraviolet and X-ray photoelectron spectroscopies, as well as angle-resolved X-ray absorption spectroscopy. We found that the HAT-CN molecules were oriented relatively face-on (40°) in the thin (5 nm) layer, whereas they were oriented relatively edge-on (62°) in the thick (100 nm) layer. By contrast, ZnPc orientation was not significantly altered by the underlying HAT-CN orientation. The highest occupied molecular orbital (HOMO) level of ZnPc was closer to the Fermi level on the 100 nm thick HAT-CN layer than on the 5 nm thick HAT-CN layer because of the higher work function. Consequently, a considerably low energy gap between the lowest unoccupied molecular orbital level of HAT-CN and the HOMO level of ZnPc was formed in the 100 nm thick HAT-CN case. This may improve the hole injection ability of the anode system, which can be utilized in various electronic devices.

Nonfullerene Agent Enables Efficient and Stable Tin‐Based Perovskite Solar Cells

Tin‐based perovskites have emerged as the most promising lead‐free perovskite materials due to the characteristics of the environmentally friendly and more suitable bandgap. However, the power conversion efficiency still lags behind the lead perovskite owing to unfavorable defects of the perovskite film and poor interface contact between tin perovskite and electron transporting layers. Herein, an n‐type conjugated nonfullerene molecule, termed IO‐4Cl, is developed for efficient and stable tin perovskite solar cells (TPSCs). The IO‐4Cl possesses electron‐donating functional groups that can enlarge grain size and passivate defect states of perovskite films through Lewis acid–base interactions. Besides, the IO‐4Cl exhibits an appropriate lowest unoccupied molecular orbital level and interface‐modification ability, enabling superior electron extraction and transport ability of TPSCs. More importantly, the hydrophobic characteristic of IO‐4Cl prevents the decomposition of perovskite films under moisture conditions, improving the moisture stability of TPSCs. Consequently, the TPSCs with IO‐4Cl achieve a champion efficiency of 11.49% with an open‐circuit voltage increase of 100 mV, and excellent moisture stability under ambient air condition with 30% relative humidity, without encapsulation. The work provides a new inspiration for the introduction of functional nonfullerene materials to obtain highly efficient and stable TPSCs.

Achieving 17.7% Efficiency of Ternary Organic Solar Cells by Incorporating a High Lowest Unoccupied Molecular Orbital Level and Miscible Third Component

A ternary strategy has been demonstrated as being an effective method to improve the power conversion efficiency (PCE); however, general rules for materials selection are not fully comprehended. Herein, nonfullerene acceptor ITIC‐M and fullerene acceptor PC70BM possessing higher lowest unoccupied molecular orbital (LUMO) and good miscibility with nonfullerene acceptor Y7 are incorporated as third components in the state‐of‐the‐art of PM6:Y7 binary blend. As a result, the device PCE for both ternary devices improves from 16.46% for binary host to 17.73% and 17.67% for ITIC‐M‐ and PC70BM‐based ternary devices, respectively. The higher LUMO of the guest acceptor can play multiple roles to elevate the open‐circuit voltage such as reducing energy‐loss and reverse saturation current, creating less‐localized shallow trap sites along with suppressing charge recombination, and decreasing Urbach energy. Moreover, the good miscibility facilitates an alloy‐like phase in acceptors domain for efficient exciton dissociation and electron transport, which leads to improved short‐circuit current density and fill factor in ternary devices. The results provide a promising approach to realize high‐performance ternary organic solar cells by synergizing the compatible third component with host acceptor.

Third component with a high LUMO energy level enables 17.69% efficiency in ternary organic solar cells

The ternary strategy is thought to be a practical method for improving the power conversion efficiency (PCE) of organic solar cells (OSCs). To create ternary OSCs, a PM6:BTP-BO-4F host blend was combined with the non-fullerene small molecule acceptor BTA3, which has a high lowest unoccupied molecular orbital (LUMO). BTA3 demonstrated complementary absorption spectra and excellent compatibility with BTP-BO-4F, which made it easier to modulate the ternary film's morphology and catch more photons. As a result, the short circuit current density increased. Additionally, BTA3's LUMO level was marginally higher than BTP- BO-4F's, which led to a higher open-circuit voltage of the TOSCs. The addition of BTA3 improved the OSCs' energy transfer and phase separation, which in turn sped up charge transfer and reduced exciton recombination. The PCE of the TOSCs included with 10 wt% BTA3 rose to 17.69% in comparison to a PCE of 16.46% based on host binary OSCs. This research demonstrated that the incorporation of BTA3 with a high LUMO level enabled the fabrication of ternary OSCs with good performance.