Bulk Heterojunction Devices Research Articles

Designed Polar Cosolvent-Prepared Zinc Oxide Film for Efficient and Stable Inverted Organic Solar Cells.

Here, a simple method of applying dimethylformamide (DMF) as cosolvent in the sol-gel technology is used to improve the quality of ZnO bulk films. First-principles calculations show that with the addition of polar solvent DMF, the adsorption energy (Eads) between the solvent and Zn(OH)₂ increases from -1.42 to -1.74eV, which can stabilize the existence of Zn(OH)₂, thereby promoting the ZnO synthesis. Besides, the elimination of amine residues in the DMF-ZnO film significantly suppress the photocatalytic activity induced by amine-induced coordination or redox reactions. Inverted organic solar cells (OSCs) based on PM6:Y6 and PM6:BTP-eC9 achieves impressive power conversion efficiencies (PCE) of 17.58 and 18.14%, respectively. Furthermore, benefiting from the reduced defects of bulk ZnO, pseudo-bilayer bulk heterojunction (PBHJ) devices based on the optimized ZnO film exhibited superior stability, the PM6:Y6 devices based on DMF-ZnO ETLs can maintain 90.28% of their initial PCE after 1000 h of thermal aging at 85°C, and 80.98% of their initial PCE after 168 h of UV aging. This simple solvent optimization strategy can significantly improve the charge transport of ZnO bulk films, making it a reliable strategy for the preparation of electron transport layers in OSCs.

Tuning the hole transporting layer using the NiO@X2C (X = W or Mo) composites for polymer solar cells and X-ray detectors

In this paper, we showcased the augmentation in power conversion efficiency (PCE) and photodetectivity of bulk heterojunction (BHJ) organic solar cells and photodetectors through the integration of functionalized metal carbides interacted NiO composites with PEDOT:PSS as a hole transport (HT) material. The 2D metal carbides (Mo2C and W2C), quintessential representatives of the MXenes family, integrated NiO were synthesized and employed to tune the HT in BHJ solar cells and photodetectors. These materials exhibit exceptional electronic conductivity, high mobility, enhanced electron extraction, excellent optical transparency, and desirable mechanical properties, rendering them as ideal candidates for enhancing the performance of BHJ devices. The constructed devices with NiO@Mo2C and NiO@W2C blended PEDOT:PSS HT achieved a PCE of ∼7.49 % and ∼8.32 %, representing the ∼28 % and ∼43 % improvement, respectively compared to the PCE obtained with the pure PEDOT:PSS active layer (PCE = 5.86 %). Additionally, the photodetector utilizing the NiO@Mo2C and NiO@W2C blended PEDOT:PSS HT demonstrated a maximum sensitivity of 2.25 and 2.62 mA/Gy·cm² better than the pure HT under X-ray irradiation. This work suggests the integration of 2D metal carbides integrated NiO into the HT as a promising approach to enhance the efficiency of BHJ devices.

The selenium substitution of solvent additive enables efficient polymer solar cells with efficiency of 19.4 %

Solvent additives, which are widely used as versatile tools for refining active layer morphology, have been considered as important role in enhancing the power conversion efficiency (PCE) of polymer solar cells (PSCs). Herein, innovative solvent additive 2,5-dibromoselenophene (BrS), is devised and synthesized by substituting the sulfur atom in 2,5-dibromothiophene (BrT) with selenium atom. The facile polarization properties of selenium atoms enable selenophene to participate in intermolecular interactions with oxygen or sulfur atoms. Therefore, incorporating BrS into the blend solution leads to refined intermolecular interactions and molecular packing, and crystallinity, resulting in a refined bulk heterojunction (BHJ) morphology compared to using the solvent additives 1-chloronaphthalene (CN) and BrT. Consequently, the BrS outperform their BrT and CN in improving photon absorption, exciton dissociation, and charge collection properties of PSCs, yielding an enhanced PCE of 18.0 % in PM6:Y6 BHJ devices. Moreover, the BrS solvent additive exhibit general applicability in both non-fullerene small molecules PSCs and all-polymer PSCs. High efficiency of 18.8 %, 19.4 % and 18.1 % are obtained in PM6:L8-BO, D18:L8-BO, and PM6:PY-IT BHJ solar cells, respectively, which is rankable among the paramount performance reported to date. Our results highlight the potential of selenophene-based solvent additives as an observable pathway for nanomorphology of active layer and effective enhancement of PCE in PSCs.

Trifluoromethylation Enables Compact 2D Linear Stacking and Improves the Efficiency and Stability of Q‐PHJ Organic Solar Cells

AbstractCompared to the bulk heterojunction (BHJ) devices, the quasiplanar heterojunction (Q‐PHJ) exhibits a more stable morphology and superior charge transfer performance. To achieve both high efficiency and long‐term stability, it is necessary to design new materials for Q‐PHJ devices. In this study, QxIC‐CF3 and QxIC‐CH3 are designed and synthesized for the first time. The trifluoromethylation of the central core exerts a modulatory effect on the molecular stacking pattern, leveraging the strong electrostatic potential and intermolecular interactions. Compared with QxIC‐CH3, the single crystal structure reveals that QxIC‐CF3 exhibits a more compact 2D linear stacking behavior. These benefits, combined with the separated electron and hole transport channels in Q‐PHJ device, lead to increased charge mobility and reduced energy loss. The devices based on D18/QxIC‐CF3 exhibit an efficiency of 18.1%, which is the highest power conversion efficiency (PCE) for Q‐PHJ to date. Additionally, the thermodynamic stability of the active layer morphology enhances the lifespan of the aforementioned devices under illumination conditions. Specifically, the T80 is 420 h, which is nearly twice that of the renowned Y6‐based BHJ device (T80 = 220 h). By combining the advantages of the trifluoromethylation and Q‐PHJ device, efficient and stable organic solar cell devices can be constructed.

Spectrally Resolved Exciton Polarizability for Understanding Charge Generation in Organic Bulk Hetero-Junction Diodes.

Despite decades of research, the dominant charge generation mechanism in organic bulk heterojunction (BHJ) devices is not completely understood. While the local dielectric environments of the photoexcited molecules are important for exciton dissociation, conventional characterizations cannot separately measure the polarizability of electron-donor and electron-acceptor, respectively, in their blends, making it difficult to decipher the spectrally different charge generation efficiencies in organic BHJ devices. Here, by spectrally resolved electroabsorption spectroscopy, we report extraction of the excited state polarizability for individual donors and acceptors in a series of organic blend films. Regardless of the donor and acceptor, we discovered that larger exciton polarizability is linked to larger π-π coherence length and faster charge transfer across the heterojunction, which fundamentally explains the origin of the higher charge generation efficiency near 100% in the BHJ photodiodes. We also show that the molecular packing of the donor and acceptor influence each other, resulting in a synergetic enhancement in the exciton polarizability.

Molecular and Heterojunction Device Engineering of Solution-Processed Conjugated Reticular Oligomers: Enhanced Photoelectrochemical Hydrogen Evolution through High-Effective Exciton Separation.

Covalent organic frameworks (COFs) face limited processability challenges as photoelectrodes in photoelectrochemical water reduction. Herein, sub-10nm benzothiazole-based colloidal conjugated reticular oligomers (CROs) are synthesized using an aqueous nanoreactor approach, and the end-capping molecular strategy to engineer electron-deficient units onto the periphery of a CRO nanocrystalline lattices (named CROs-Cg). This results in stable and processable "electronic inks" for flexible photoelectrodes. CRO-BtzTp-Cg and CRO-TtzTp-Cg expand the absorption spectrum into the infrared region and improve fluorescence lifetimes. Heterojunction device engineering is used to develop interlayer heterojunction and bulk heterojunction (BHJ) photoelectrodes with a hole transport layer, electron transport layer, and the main active layers, using a CROs/CROs-Cg or one-dimensional (1D) electron-donating polymer HP18 mixed solution via spinning coating. The ITO/CuI/CRO-TtzTp-Cg-HP18/SnO2/Pt photoelectrode shows a photocurrent of 94.9µA cm‒2 at 0.4V versus reversible hydrogen electrode (RHE),which is 47.5 times higher than that of ITO/Bulk-TtzTp. Density functional theory calculations show reduced energy barriers for generating adsorbed H* intermediates and increased electron affinity in CROs-Cg. Mott-Schottky and charge density difference analyses indicate enhanced charge carrier densities and accelerated charge transfer kinetics in BHJ devices. This study lays the groundwork for large-scale production of COF nanomembranes and heterojunction structures, offering the potential for cost-effective, printable energy systems.

Optimizing Spin-Coat Speed for Fabrication of P3HT: PCBM Solar Cells

The effect of spin speed on the orientation of the conjugated polymer chains becomes a matter of concern while fabricating bulk heterojunction devices such as solar cells. The stability and performance strongly depend on the intertwining of the two molecules that form the bulk heterojunctions. In the case of P3HT: PCBM, it is the long chains of P3HT that encompasses the PCBM molecules. This work investigates the fabricating conditions of Poly (3-hexylthiophene) (P3HT) on the glass substrates in terms of spin coating speeds to obtain favourable geometry of P3HT. For this purpose, three different samples were prepared, keeping spin rate as 6850, 8150 and 9700 rpm, respectively. It was observed that at high spin rates, a large centrifugal force acts upon polymer chains, unfolding them into highly oriented structures. These P3HT chains are free from twists, kinks and are not intermingled. The results of the present work advocate fabricating P3HT: PCBM films at spin speeds less than 6850 rpm.

Comparative performance analysis of poly (3-hexylthiophene-2, 5-dial) and [6,6]-phenyl-C61 butyric acid methyl ester-based organic solar cells in bulk-heterojunction and bilayer structure using SCAPS

This work is concerned with the design and photovoltaic performance study of organic semiconducting materials-based solar cells using a SCAPS simulator. Organic solar cells are one form that absorbs light and produces electricity. They exhibit high power conversion efficiency, low manufacturing costs, lightweight, and flexibility which makes them a promising technology for renewable energy. We developed and designed organic solar cell devices with the structure ITO/PEDOT: PSS/P3HT: PCBM/PFN-Br/Al for bulk-heterojunction structure and ITO/PEDOT: PSS/P3HT: PCBM/PFN-Br/Al for bilayer structure where PEDOT: PSS and PFN-Br were used as hole and electron transporting layers (HTL and ETL) respectively. The short circuit current density versus voltage (J-V) characteristics as well as photovoltaic parameters namely open circuit voltage (VOC), short circuit current density (JSC), fill factor (FF), and power conversion efficiency (PCE) have been examined. In addition, the quantum efficiency (QE) of the two structures has been also studied. The effectiveness of the photovoltaic simulated systems has also been attempted to be enhanced by varying the absorber layer's thickness for both architectures. Later, this turned out that variations in the band gap of the absorber layer had an impact on the factors that determined how well solar cells performed. It has been found that the simulated bulk-heterojunction device exhibits 20.43% PCE whereas 3.52% PCE has been calculated from the simulated bilayer device.

Polymer-Entangled Spontaneous Pseudo-Planar Heterojunction for Constructing Efficient Flexible Organic Solar Cells.

Flexible organic solar cells (FOSCs) have attracted considerable attention from researchers as promising portable power sources for wearable electronic devices. However, insufficient power conversion efficiency (PCE), intrinsic stretchability, and mechanical stability of FOSCs remain severe obstacles to their application. Herein, an entangled strategy is proposed for the synergistic optimization of PCE and mechanical properties of FOSCs through green sequential printing combined with polymer-induced spontaneous gradient heterojunction phase separation morphology. Impressively, the toughened-pseudo-planar heterojunction (Toughened-PPHJ) film exhibits excellent tensile properties with a crack onset strain (COS) of 11.0%, twice that of the reference bulk heterojunction (BHJ) film (5.5%), which is among the highest values reported for the state-of-the-art polymer/small molecule-based systems. Finite element simulation of stress distribution during film bending confirms that Toughened-PPHJ film can release residual stress well. Therefore, this optimal device shows a high PCE (18.16%) with enhanced (short-circuit current density) JSC and suppressed energy loss, which is a significant improvement over the conventional BHJ device (16.99%). Finally, the 1cm2 flexible Toughened-PPHJ device retains more than 92% of its initial PCE (13.3%) after 1000 bending cycles. This work provides a feasible guiding idea for future flexible portable power supplies.

Achieving Desired Pseudo-Planar Heterojunction Organic Solar Cells via Binary-Dilution Strategy.

The sequential deposition process has demonstrated the great possibility to achieve a photolayer architecture with an ideal gradient phase separation morphology, which has a vital influence on the physical processes that determine the performance of organic solar cells (OSCs). However, the controllable preparation of pseudo-planar heterojunction (P-PHJ) with gradient distribution has not been effectively elucidated. Herein, a binary-dilution strategy is proposed, the PM6 solution with micro acceptor BO-4Cl and the L8-BO solution with micro donor PM6 respectively, to form P-PHJ film. This architecture exists good donor (D) and acceptor (A) vertical gradient distribution and larger D/A interpenetrating regions, which promotes exciton generation and dissociation, shortens charge transport distance and optimizes carrier dynamics. Moreover, the dilution of PM6 by BO-4Cl promotes the regulation of active layer aggregation size and phase purity, thus alleviating energy disorder and voltage loss. As a result, the P-PHJ device exhibits an outstanding power conversion efficiency of 19.32% with an excellent short-circuit current density of 26.92mA cm-2 , much higher than planar binary heterojunction (17.67%) and ternary bulk heterojunction (18.49%) devices. This research proves a simple but effective method to provide an avenue for constructing desirable active layer morphology and high-performance OSCs.

Different Energetics at Donor:Acceptor Interfaces in Bilayer and Bulk‐Heterojunction Polymer:Non‐Fullerene Organic Solar Cells

To understand the limitations placed on the open‐circuit voltage of bulk heterojunction (BHJ) organic solar cells, the energy levels of neat donor and acceptor samples are often characterized and applied to study BHJ blends. However, energy levels derived from neat samples may not necessarily reflect those at the donor:acceptor interface in blends. The properties of organic semiconductors are sensitive to microstructural changes, with non‐fullerene acceptors (NFAs) in particular known to exhibit different thin‐film polymorphs. To investigate the influence of differences in molecular packing in neat and blend films, temperature‐dependent current–voltage characteristics are measured for bilayer (BL) and BHJ devices. Herein, the fullerene acceptor PC71BM is compared—whose energy levels are expected to be less sensitive to molecular packing—with the NFA ITIC, paired with the same donor polymer PTB7‐Th. It is found that the interfacial energy levels differ for BL and BHJ devices for the PTB7‐Th:ITIC system but remain the same for the PTB7‐Th:PC71BM system. Furthermore, X‐ray scattering measurements identify that ITIC exhibits a different packing mode in neat films and in BHJ blends. Such microstructure‐dependent differences between neat and blend samples need to be considered when studying energy losses in NFA BHJ solar cells.

Enhanced Self-Stimulated Dissociation in Non-fullerene Layer-by-Layer Organic Solar Cells through Superimposed and Oriented Dipolar Polarization

A non-fullerene layer-by-layer (LBL) structure can establish effective donor/acceptor (D/A) interfaces and lead to remarkable photovoltaic efficiencies based on facile solution processing properties, as compared with non-fullerene bulk heterojunction devices. However, the operating mechanisms have been remaining as an unaddressed issue to understand the role of D/A interfaces toward developing photovoltaic processes in non-fullerene LBL where the high electrically polarizable non-fullerene molecules exist. Here, we address the operating mechanisms of photovoltaic actions by in situ monitoring the dynamic D/A interfaces upon selectively exciting the non-fullerene acceptor layer to address the effects of optically induced superimposed and oriented dipoles on electron–hole pair self-stimulated dissociation in non-fullerene LBL organic solar cells [ITO/PEDOT:PSS/PM6/Y6/PDIN/Al]. Essentially, the self-stimulated dissociation at the D/A interfaces can be monitored by magneto-photocurrent while separately exciting the donor and acceptor components with two different laser beams. We observed an interesting phenomenon that optically exciting the non-fullerene Y6 acceptor component leads to easier electron–hole dissociation at D/A interfaces and consequently an increase on electron–hole pair self-stimulated dissociation to generate photocurrent in non-fullerene LBL solar cells. This phenomenon presents a hypothesis that optically exciting the compactly stacked non-fullerene Y6 molecules induces superimposed and oriented electrical dipoles within A–D–A–D–A structures to increase the self-stimulated dissociation at D/A interfaces toward developing the photovoltaic actions in non-fullerene LBL solar cells. This hypothesis is supported by our photoinduced capacitance result: photoexcitation increases bulk polarization in the dipolar polarization zone in non-fullerene LBL solar cells. Furthermore, optically generated dipoles are verified by photoinduced magneto-capacitance, solely generated by photoinduced polarization rather than photogenerated carriers, in non-fullerene LBL PM6/Y6. Clearly, the optically generating superimposed and oriented electrical dipoles become a critical parameter to operate the photovoltaic actions at D/A interfaces in non-fullerene LBL solar cells.

Fabrication and Characterization of Hybrid Films Based on NiFe2O4 Nanoparticles in a Polymeric Matrix for Applications in Organic Electronics.

Hybrid films for applications in organic electronics from NiFe2O4 nanoparticles (NPs) in poly(3,4 ethylene dioxythiophene), poly(4-styrenesulfonate) (PEDOT:PSS), and poly(methyl methacrylate) (PMMA) were fabricated by the spin-coating technique. The films were characterized by infrared spectroscopy, atomic force microscopy, scanning electron microscopy, and energy-dispersive spectroscopy to subsequently determine their optical parameters. The electronic transport of the hybrid films was determined in bulk heterojunction devices. The presence of NiFe2O4 NPs reinforces mechanical properties and increases transmittance in the hybrid films; the PEDOT:PSS-NiFe2O4 NPs film is the one that has a maximum stress of 28 MPa and a Knoop hardness of 0.103, while the PMMA-NiFe2O4 NPs film has the highest transmittance of (87%). The Tauc band gap is in the range of 3.78-3.9 eV, and the Urbach energy is in the range of 0.24-0.33 eV. Regarding electrical behavior, the main effect is exerted by the matrix, although the current carried is of the same order of magnitude for the two devices: glass/ITO/polymer-NiFe2O4 NPs/Ag. NiFe2O4 NPs enhance the mechanical, optical, and electrical behavior of the hybrid films and can be used as semi-transparent anodes and as active layers.

Layer‐by‐Layer‐Processed Organic Solar Cells with 18.02% Efficiency Enabled by Regulating the Aggregation of Bottom Polymers

The fabrication of organic solar cells (OSCs) by a layer‐by‐layer (LBL) method has attracted growing attention in recent years. As already known, the pre‐aggregates of conjugated polymers in solution have a profound impact on their microstructure morphology in films. Herein, by simply controlling the solution temperature and annealing processes, the pre‐aggregation behavior of D18 polymer in solution can be fine‐tuned and the microstructure of D18 bottom layer is well manipulated. The optimized D18 bottom layer can effectively regulate L8‐BO upper‐layer‐forming suitable networks for efficient charge transportation. In addition, a vertical phase separation with a special D/D:A/A structure (P‐i‐N‐type component distribution) is also formed. As a result, compared to the 16.43% power conversion efficiency (PCE) of the bulk heterojunction devices, such control enables bilayer OSC devices based on the polymer D18 and L8‐BO to deliver an enhanced PCE of 18.02% with simultaneously improved short‐circuit current density, open‐circuit voltage, and fill factor. It is also demonstrated in these results that the LBL deposition process utilizing the pre‐aggregation of polymer and its fiber‐network‐forming ability is a very promising approach to improve charge dynamics, suppress carrier recombination, and fabricate highly efficient OSCs.

Molecular orientation-dependent energetic shifts in solution-processed non-fullerene acceptors and their impact on organic photovoltaic performance

The non-fullerene acceptors (NFAs) employed in state-of-art organic photovoltaics (OPVs) often exhibit strong quadrupole moments which can strongly impact on material energetics. Herein, we show that changing the orientation of Y6, a prototypical NFA, from face-on to more edge-on by using different processing solvents causes a significant energetic shift of up to 210 meV. The impact of this energetic shift on OPV performance is investigated in both bilayer and bulk-heterojunction (BHJ) devices with PM6 polymer donor. The device electronic bandgap and the rate of non-geminate recombination are found to depend on the Y6 orientation in both bilayer and BHJ devices, attributed to the quadrupole moment-induced band bending. Analogous energetic shifts are also observed in other common polymer/NFA blends, which correlates well with NFA quadrupole moments. This work demonstrates the key impact of NFA quadruple moments and molecular orientation on material energetics and thereby on the efficiency of high-performance OPVs.

Pentacoordinated Organotin(IV) Complexes as an Alternative in the Design of Highly Efficient Optoelectronic and Photovoltaic Devices: Synthesis and Photophysical Characterization

The synthesis of four pentacoordinated organotin(IV) complexes prepared in a one-pot reaction from 2-hydroxy-1-naphthaldehyde, 2-amino-3-hydroxypyridine and organotin oxides is reported. The complexes were characterized by UV-Vis, IR, MS, 1H, 13C and 119Sn NMR techniques. The compound based on 2,2-diphenyl-6-aza-1,3-dioxa-2-stannanaphtho[1,2-h]pyrido[3,2-d]cyclononene revealed the formation of a monomeric complex with a distorted five-coordinated molecular geometry intermediate between the trigonal bipyramidal and square pyramidal. In order to find possible applications in photovoltaic devices, hybrid films of organotin(IV) complexes embedded in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with graphene were deposited. The topographic and mechanical properties were examined. The film with the complex integrated into the cyclohexyl substituent has high plastic deformation, with a maximum stress of 1.69 × 107 Pa and a Knoop hardness of 0.061. The lowest values of 1.85 eV for the onset gap and 3.53 eV for the energy gap were obtained for the heterostructure having the complex with the phenyl substituent. Bulk heterojunction devices were fabricated; these devices showed ohmic behavior at low voltages and a space-charge-limited current (SCLC) conduction mechanism at higher voltages. A value of 0.02 A was found for the maximum carried current. The SCLC mechanism suggests hole mobility values of between 2.62 × 10-2 and 3.63 cm2/V.s and concentrations of thermally excited holes between 2.96 × 1018 and 4.38 × 1018 m-3.

Facile Synthesis of Key Building Blocks of D18 Series Conjugated Polymers for High-Performance Polymer Solar Cells

D18 and its derivatives (such as D18-Cl) newly emerged as high-performance conjugated polymers for bulk heterojunction (BHJ) solar cells, with efficiency breaching 17% when paired with small molecule acceptors such as Y6 and its derivatives. However, the complex synthesis of D18 series has limited their accessibility to the research community. We redesigned the original synthetic scheme of D18, particularly the key monomer, 5,8-bis(5-bromo-4-(2-butyloctyl)thiophen-2-yl)dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2-c][1,2,5]thiadiazole (Br2-T2-DTBT), and replaced a few key steps in the original scheme that were hard to reproduce and/or low yielding with simple to operate and high yielding reactions. Carother’s equation was successfully applied to control/tune the molar mass of D18-Cl, and three representative molar masses (high, medium, and low) of D18-Cl were subject to device testing. It is discovered that a medium molar mass (56 kg/mol) D18-Cl offered the highest performance (average 16.6%) when paired with Y6 as the acceptor in a typical BHJ device configuration, consistent with the literature report. This optimized synthesis of D18 series offers great synthetic tunability, and the modular nature/optimized key reactions will facilitate the design and synthesis of conjugated polymers for optoelectronics.

Low Temperature Sequential Deposition Strategy for High Performance Pseudoplanar Heterojunction Semitransparent Organic Photovoltaics

AbstractSemitransparent organic photovoltaics (ST‐OPVs) have great application potential in photovoltaic buildings and wearable devices. Studies have proved that power conversion efficiency (PCE) and average visible transmittance (AVT) reveal more balanced in pseudoplanar heterojunction (PPHJ) structure than in bulk heterojunction (BHJ) structure. An interesting approach named low temperature sequential deposition (LTSD)—spin‐coating the small molecule acceptor (A) Y6 on polymer donor (D) PM6—is proposed to form an efficient PPHJ structure. In the LTSD process, small molecule Y6 will diffuse through amorphous PM6 layer which means that Y6 finally aggregates at the bottom of active layer and results in vertical gradient concentration distribution. In this structure, adjustment of D:A ratio can achieve higher AVT with maintaining less PCE loss compared with BHJ structure. The fabricated LTSD devices provide PCE of 12.36% (AVT of 23.19%) at 45:40 nm (D:A layer thickness) and PCE of 11.26% (AVT of 25.10%) at 40:40 nm (D:A), while BHJ devices provide PCE of 11.43% (AVT of 21.32%) at 85 nm (D:A = 1:1.2 w). Besides, the LTSD devices are more stable than BHJ devices due to smoother surface. LTSD strategy provides a new approach for achieving PPHJ structure and high‐performance ST‐OPVs.

Desirable Uniformity and Reproducibility of Electron Transport in Single-Component Organic Solar Cells.

Despite the simplified fabrication process and desirable microstructural stability, the limited charge transport properties of block copolymers and double-cable conjugated polymers hinder the overall performance of single-component photovoltaic devices. Based on the key distinction in the donor (D)-acceptor (A) bonding patterns between single-component and bulk heterojunction (BHJ) devices, rationalizing the difference between the transport mechanisms is crucial to understanding the structure-property correlation. Herein, the barrier formed between the D-A covalent bond that hinders electron transport in a series of single-component photovoltaic devices is investigated. The electron transport in block copolymer-based devices is strongly dependent on the electric field. However, these devices demonstrate exceptional advantages with respect to the charge transport properties, involving high stability to compositional variations, improved film uniformity, and device reproducibility. This work not only illustrates the specific charge transport behavior in block copolymer-based devices but also clarifies the enormous commercial viability of large-area single-component organic solar cells (SCOSCs).

Mediation of exciton concentration on magnetic field effects in NPB : Alq3-based heterojunction OLEDs.

Organic light-emitting diodes (OLEDs) are considered one of the most promising new display technologies owing to their advantages, such as all-solid-state, high color gamut, and wide viewing angle. However, in terms of special fields, the brightness, lifetime, and stability of the devices need further improvement. Therefore, heterojunction devices with different concentrations were prepared to regulate device brightness. The brightness of the bulk heterojunction device is enhanced by 9740 cd m-2, with a growth rate of about 26.8%. The impact of various temperatures and various exciton concentrations on the device magneto-conductance (MC) and magneto-electroluminescence (MEL) was investigated. Experimental results demonstrate that the exciton concentration inside the device can be tuned to improve optoelectronic properties and organic magnetic effects. The complex spin mixing process inside the bulk heterojunction device is deeply investigated, which provides a reliable basis for the design of bulk heterojunction devices.