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HighlightsA solid additive-assisted layer-by-layer (SAA-LBL) processing was developed to facilitate the inter-diffusion between polymer donor and acceptor and optimize the morphology of quasi-planar heterojunction for high-performance organic solar cells (OSCs).The pre-phase separation between fatty acid and polymer donor, easily tuned via controlling the cohesive energy, is critical to form the desired vertical phase-separation morphology.The SAA-LBL is generally applicable to various OSC systems, and enables the record efficiency of 19.02% among the binary OSCs.Morphology is of great significance to the performance of organic solar cells (OSCs), since appropriate morphology could not only promote the exciton dissociation, but also reduce the charge recombination. In this work, we have developed a solid additive-assisted layer-by-layer (SAA-LBL) processing to fabricate high-efficiency OSCs. By adding the solid additive of fatty acid (FA) into polymer donor PM6 solution, controllable pre-phase separation forms between PM6 and FA. This intermixed morphology facilitates the diffusion of acceptor Y6 into the donor PM6 during the LBL processing, due to the good miscibility and fast-solvation of the FA with chloroform solution dripping. Interestingly, this results in the desired morphology with refined phase-separated domain and vertical phase-separation structure to better balance the charge transport /collection and exciton dissociation. Consequently, the binary single junction OSCs based on PM6:Y6 blend reach champion power conversion efficiency (PCE) of 18.16% with SAA-LBL processing, which can be generally applicable to diverse systems, e.g., the PM6:L8-BO-based devices and thick-film devices. The efficacy of SAA-LBL is confirmed in binary OSCs based on PM6:L8-BO, where record PCEs of 19.02% and 16.44% are realized for devices with 100 and 250 nm active layers, respectively. The work provides a simple but effective way to control the morphology for high-efficiency OSCs and demonstrates the SAA-LBL processing a promising methodology for boosting the industrial manufacturing of OSCs.

PurposeComplex technology not only provides potential economic benefits but also increases the difficulty of application. Whether and how upstream technological complexity affects downstream manufacturers' innovation through vertical separation structure is worth discussing, but it has not been effectively discussed.Design/methodology/approachThrough theoretical analysis and empirical testing, this article discusses the cost effect and market competition effect caused by upstream technological complexity on downstream manufacturers and further elucidates the impact of upstream technological complexity on downstream manufacturers' innovation.FindingsResearch has found that the impact of upstream technological complexity on the downstream manufacturers' innovation depends on the cost effect and market competition effect. The cost effect caused by the complexity of upstream technology inhibits the innovation of downstream manufacturers. In contrast, the market competition effect promotes the innovation of downstream manufacturers. There are differences in the cost effect and market competition effect of upstream technological complexity on different types of downstream manufacturers, so there is also significant heterogeneity in the impact of upstream technological complexity on innovation of different types of downstream manufacturers.Originality/valueThe conclusions of this article improve the understanding of the relationship between upstream technological complexity and downstream innovation and provide helpful implications for industrial chain innovation.

Layer-by-layer (LbL) strategy has been developed to form bulk heterojunction (BHJ) structure for processing efficient organic solar cells (OSCs). Herein, LbL slot-die coating with twin boiling point solvents (TBPS) strategy was developed to fabricate highly efficient OSCs, which matches with large-scale, high throughput roll-to-roll (R2R) industrialized mass process. The TBPS strategy could produce high-quality thin film without any additive, leading to the optimized vertical phase separation with interpenetrating nanostructures, as well as the enhanced charge transport and extraction. Thus, the power conversion efficiency up to 14.42% was achieved for [(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)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)]:2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2″,3″:4″,5″]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene)) bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (PM6:Y6) OSCs fabricated via sequentially LbL slot-die coating using the TBPS strategy under ambient condition. The research provides a potential route for industrialized production of high-efficiency and large-area OSC devices.

Many coastal communities rely on individual onsite wastewater treatment (i.e., septic) systems to treat and disperse wastewater. Proper wastewater treatment in these systems depends on sufficient volume of unsaturated soil below the drainfield’s infiltrative surface. This is governed by the vertical separation distance—the distance between the groundwater table and the drainfield infiltrative surface—which is specified in (regulatory jurisdictions’ onsite wastewater system) regulations. Groundwater tables along the southern New England coast are rising due to sea-level rise, as well as changes in precipitation and water use patterns, which may compromise the functioning of existing septic systems. We used long-term shallow groundwater monitoring wells and ground-penetrating radar surveys of 10 drainfields in the southern Rhode Island coastal zone to determine whether septic system drainfields have adequate separation distance from the water table. Our results indicate that only 20% of tested systems are not impaired by elevated groundwater tables, while 40% of systems experience compromised separation distance at least 50% of the time. Surprisingly, 30% of systems in this study do not meet separation distance requirements at any time of the year. Neither age of system nor a system’s geographical relationship to a tidal water body was correlated with compromised separation distance. The observed compromised separation distances may be a result of inaccurate methods, specified by the regulations, to determine the height of the seasonal high water table. Our preliminary results suggest that enacting changes in the regulatory permitting process for coastal zone systems may help protect coastal drinking and surface water resources.

The morphology of organic films plays a pivotal role in determining the performance of transistor devices. While the dip-coating technique is capable of producing highly oriented organic films, it often encounters challenges such as limited coverage and the presence of defects in gaps between strips, adversely affecting device performance. In this study, we address these challenges by increasing solution viscosity through the incorporation of a substantial proportion of dielectric polymers, thereby enhancing the participation of additional molecules during the film formation process when pulled up. This method produces continuous and oriented organic films with a notable absence of gaps, significantly improving the carrier mobility of transistor devices by more than twofold. Importantly, the fabricated devices exhibit remarkable reliability, showing no hysteresis even after 200 cycles of measurement. Furthermore, the current and threshold voltages of the devices demonstrate exceptional stability, maintaining steady after 10,000 s of bias measurement. This approach provides a solution for the cost-effective and large-scale production of organic transistors, contributing significantly to the advancement of organic electronics.

Non-fullerene organic solar cell (NFOSC) has attracted tremendous attention due to their great potential for commercial applications. To improve its power conversion efficiency (PCE), generally, sequential solution deposition (SSD) methods have been employed to construct the graded vertical phase separation (VPS) of the bulk-heterojunction (BHJ) active layer for efficient exciton separation and charge transition. However, a variety of orthogonal solvents used in the SSD may lead to the unpredicted change in the BHJ morphology and introduce additional defects inside the BHJ bulk thus complicate the fabrication process. Here, a simple oscillating stratification preprocessing (OSP) is developed to facilitate the formation of graded VPS among the BHJ layer. As a result, a significant improvement is obtained in PCE from 10.96% to 12.03%, which is the highest value reported among PBDB-T: ITIC based NFOSC.

In comparison to widely adopted bulk heterojunction (BHJ) structures for organic solar cells (OSC), exploiting the sequential deposition to form planar heterojunction (PHJ) structures enables to realize the favorable vertical phase separation to facilitate charge extraction and reduce charge recombination in OSCs. However, effective tunings on the power conversion efficiency (PCE) in PHJ-OSCs are still restrained by the currently available methods. Based on a polymeric donor PBDBT-2F (PBDBT=Poly [[4,8-bis [5-(2-ethylhexyl)-4-fluoro-2-thienyl]benzo [1,2-b:4,5- b′ ]dithiophene-2,6-diyl]-2,5-thiophenediyl [5,7-bis (2-ethylhexyl)-4,8-dioxo-4 H ,8 H -benzo [1,2- c :4,5- c′ ]dithiophene-1,3-diyl]-2,5-thiophenediyl]) and a non-fullerene (NF) acceptor Y6, we proposed a strategy to improve the properties of photovoltaic performances in PHJ-based OSCs through dilute dispersions of the PBDBT-2F donor into the acceptor-dominant phase with the sequential film deposition. With the control of donor dispersions, the charge transport balance in the PHJ-OSCs is improved, leading to the expedited photocarrier sweep-out with reduced bimolecular charge recombination. As a result, a PCE of 15.4% is achieved in the PHJ-OSCs. Importantly, the PHJ solar cells with donor dispersions exhibit better thermal stability than corresponding BHJ devices, which is related to the better film morphology robustness and less affected charge sweep-out during the thermal aging.

Planar heterojunction (PHJ) is employed to obtain proper vertical phase separation for highly efficient polymer solar cells (PSCs). However, it heavily relies on the choice of orthogonal solvent in the production process. Here, we fabricated a pseudo-bilayer bulk heterojunction (PBHJ) PSC with cross-distribution in the vertical direction by preparing two layers of PM6 and BTP-eC9 blends in an o-XY solution with different dilution ratios to study the morphological evolution of PBHJ film. We found that the PBHJ film exhibits more uniform and suitable continuous interpenetrating network morphology and proper phase separation in the vertical direction for the formation of p-i-n structure. This provides an effective channel for exciton dissociation and charge transport, which is confirmed by both exciton generation simulations and charge dynamics measurements. The PBHJ devices can effectively inhibit trap recombination and accelerate charge separation and transfer. Based on good active layer morphology and balanced charge mobility, all-green solvent-processed PSCs with champion power conversion efficiencies (PCEs) of 18.48% and 16.83% are obtained in PM6:BTP-eC9 and PTQ10:BTP-eC9 systems, respectively. This work reveals the potential mechanism of morphological evolution induced by the PBHJ structure and provides an alternative approach for developing solution processing PSCs.

The ternary blending strategy is a fundamental approach that is widely recognized in the field of organic optoelectronics. In our investigation, leveraging the inherent advantages of the ternary component blending methodology, we introduced an innovative design for organic photodetectors (OPDs) aimed at reducing the dark current density (Jd) under reverse bias. This pioneering effort involved combining two distinct conjugated molecules (IT-4F and IEICO-4F) with a conjugated polymer (PM7), resulting in a composite material characterized by a well-defined vertical phase separation. To thoroughly explore device performance variations, we utilized a comprehensive array of analytical techniques, including atomic force microscopy (AFM) cross-section methodologies and Kelvin probe force microscopy (KPFM). Through the optimization of the blend ratio (PM7:IT-4F: IEICO-4F at 1:0.8:0.2), we achieved significant advancements. The resulting OPD demonstrated an exceptional reduction in JD, reaching a remarkably low value of 4.95 × 10−10 A cm−2, coupled with an ultra-high detectivity of 4.95 × 1013 Jones and an outstanding linear dynamic range exceeding 100 dB at 780 nm under a bias of −1V. Furthermore, the attained cutoff frequency reached an impressive 220 kHz, highlighting substantial improvements in device performance metrics. Of particular significance is the successful translation of this technological breakthrough into real-world applications, such as in heart rate sensing, underscoring its tangible utility and expanding its potential across various fields. This demonstrates its practical relevance and underscores its versatility in diverse settings.

The development of high-performance non-fullerene acceptors with extended exciton diffusion lengths has positioned the sequential layer-by-layer (LBL) solution processing technique as a promising approach for fabricating high-performance and large-area organic solar cells (OSCs). This method allows for the independent dissolution and deposition of donor and acceptor materials, enabling precise morphology control. In this review, we provide a comprehensive overview of the LBL processing technique, focusing on the morphology of the active layer. The swelling-intercalation phase-separation (SIPS) model is introduced as the mainstream theory of morphology evolution, with a detailed discussion on vertical phase separation. We summarize recent strategies for morphology optimization. Additionally, we review the progress in LBL-based large-area device and module fabrication, as well as green processing approaches. Finally, we highlight current challenges and future prospects, paving the way for the commercialization of LBL-processed OSCs.