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1. Polymerized small molecule acceptors featuring hydrogen-bonded flexible spacers enhance the efficiency and stretchability of organic solar cells

   https://doi.org/10.35848/1347-4065/adba69  

   Zhang, Di; Liu, Junfeng; Wang, Zhenye; Li, Rui; Wang, Zhi; Aldubayan, Abdulaziz; Shao, Ming; Facchetti, Antonio (March 2025, Japanese Journal of Applied Physics)

   Abstract High power conversion efficiency (PCE) and mechanical robustness are essential for organic solar cells (OSCs) used in wearable electronics. In this paper, we report a polymerized small molecular acceptor, PNH, achieved by incorporating hydrogen-bonding (H-bonding) urea flexible spacers (FS) into a Y5-OD-like polymer backbone. Fourier transform infrared spectroscopy corroborates the formation of strong H-bonding (N-H···O=C) between the carbonyl unit in the donor polymer PBDB-T and the amine group in PNH, as well as within the PNH acceptors. Furthermore, a control Y5-OD polymer (PCO) incorporating a carbonate FS unit, thus incapable of H-bonding with PBDB-T was investigated. Notably, the PBDB-T:PNH blend achieved a power conversion efficiency (PCE) of 12.1% outperforming the PBDB-T:PCO device (10.8%). This improved PCE is attributed to the enhanced molecular aggregation and charge transport induced by H-bonding interactions. Moreover, the introduction of H-bonding via FS incorporation effectively dissipates the strain energy under mechanical deformations. Thus, blend films exhibit an improved crack-onset strain from 12.16% (PBDB-T:PNH) to 18.02% (PBDB-T:PCO). Importantly, intrinsically stretchable OSCs (is-OSCs) based on the PBDB-T:PNH blend retain 70% of its initial PCE under a 25% strain. Our results highlight the role of incorporating H-bonding FS into the PSMA backbone to enhance both PCE and mechanical stretchability. 

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2. New D‐A‐A’‐Configured Small Molecule Donors Employing Conjugation to Red‐shift the Absorption for Photovoltaics

   https://doi.org/10.1002/asia.202000635  

   Wang, Chun‐Kai; Che, Xiaozhou; Lo, Yuan‐Chih; Li, Ya‐Ze; Wang, Yung‐Hao; Forrest, Stephen R.; Liu, Shun‐Wei; Wong, Ken‐Tsung (June 2020, Chemistry – An Asian Journal)

   Four new donor-acceptor-acceptor' (D-A-A')-configured donors, CPNT, DCPNT, CPNBT, and DCPNBT equipped with naphtho[1,2-c:5,6-c']bis([1,2,5]-thiadiazole) (NT) or naphtho[2,3-c][1,2,5]thiadiazole (NBT) as the central acceptor (A) unit bridging triarylamine donor (D) and cyano or dicyanovinylene acceptor (A'), were synthesized and characterized. All molecules exhibit bathochromic absorption shifts as compared to those of the benzothiadiazole (BT)-based analogues owing to improved electron-withdrawing and quinoidal character of NT and NBT cores that lead to stronger intramolecular charge transfer. Favorable energy level alignments with C70 , together with the good thermal stability and the antiparallel dimeric packing render CPNT and DCPNT suitable donors for vacuum-processed organic photovoltaics (OPV)s. OPVs based on DCPNT : C70 active layers displayed the best power conversion efficiency (PCE)=8.3%, along with an open circuit voltage of 0.92 V, a short circuit current of 14.5 mA cm-2 and a fill factor of 62% under 1 sun intensity, simulated AM1.5G illumination. Importantly, continuous light-soaking with AM 1.5G illumination has verified the durability of the devices based on CPNT:C70 and DCPNT : C70 as the active blends. The devices were examined for their feasibility of indoor light harvesting under 500 lux illumination by a TLD-840 fluorescent lamp, giving PCE=12.8% and 12.6%, respectively. These results indicate that the NT-based D-A-A'-type donors CPNT and DCPNT are potential candidates for high-stability vacuum-processed OPVs suitable for indoor energy harvesting. 

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3. Enhancing long-term morphological stability in BHJ organic solar cells through thermocleavable sidechains under continuous thermal stress

   https://doi.org/10.1039/D5SC06155E  

   Zhao, Haoyu; Shanahan, Jordan; Oh, Jiyeon; Upreti, Saroj; Ma, Guorong; You, Wei; Gu, Xiaodan (March 2026, Chemical Science)

   Organic solar cells (OSCs) have recently achieved power conversion efficiencies (PCEs) exceeding 20%; however, their long-term operational stability remains a significant barrier to commercialization. A key factor in ensuring sustained device performance is the morphological stability of the bulk heterojunction (BHJ) layer, which is closely linked to the mobilities of the donor and acceptor materials. In this study, we introduce a strategy to enhance morphological and thermal stability by incorporating thermocleavable side chains into both the donor and acceptor components of the active layer. Specifically, we employed a thermocleavable side-chain (TCS) containing conjugated polymer donor, PffBT-4T-TCS, and a similarly functionalized fullerene acceptor, C60-TCS. Upon complete thermal cleavage of the alkyl side chains, the backbone glass transition temperature of PffBT-4T-TCS increased by 60 °C. To assess the morphological stability of the thermocleaved BHJ, we utilized atomic force microscopy coupled with infrared spectroscopy (AFM-IR) to analyze films before and after thermal treatment. Our results demonstrate that the BHJ morphology remains remarkably stable after cleavage, maintaining consistent donor/acceptor composition and surface roughness for over 10 weeks at 85 °C thermal stress conditions. Normalized PCE measurements further confirm that this thermocleavable side-chain strategy offers a promising route to achieve both high efficiency and long-term stability in OSC devices. 

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4. Influence of In Situ and Ex Situ Heat Treatments on the Mechanical Behavior of LPBF-Fabricated Fe–Mn–Al–Ni Shape Memory Alloys

   https://doi.org/10.1007/s40830-025-00544-x  

   Algamal, Anwar; Gandhi, Umesh; Qattawi, Ala (June 2025, Shape Memory and Superelasticity)

   Abstract This study investigates the fabrication of Fe–Mn–Al–Ni iron-based shape memory alloys (SMAs) using laser powder bed fusion (LPBF) across a range of laser powers. The influence of energy input on material properties was assessed by evaluating the resulting volumetric energy density. Samples were produced under both as-built conditions and subjected to in situ and ex situ treatments to enhance performance. Mechanical properties were characterized through macro-indentation, Profilometry-based Indentation Plastometry (PIP), and nanoindentation techniques, while room-temperature compression testing was conducted to assess superelastic behavior. Microstructural and phase variations were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that increasing the fabrication power improved the mechanical properties of the as-built SMAs, with the optimal performance achieved at 175 W. In situ/ex situ treatments led to a significant reduction in strength but enhanced ductility by up to 39%, along with a 52% reduction in microhardness for samples fabricated at 175 W. Overall, the LPBF-produced Fe–Mn–Al–Ni SMAs exhibited good strain recovery and stability, comparable to those produced by conventional methods. This work demonstrates the potential of LPBF in developing Fe–Mn–Al–Ni SMAs with properties matching traditionally manufactured counterparts. Graphical Abstract Mechanical behavior and microstructural features of LPBF-fabricated Fe–Mn–Al–Ni SMA under the effects of in situ and ex situ treatments 

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5. Unlocking enhanced thermal conductivity in polymer blends through active learning

   https://doi.org/10.1038/s41524-024-01261-2  

   Xu, Jiaxin; Luo, Tengfei (December 2024, npj Computational Materials)

   Abstract Polymers play an integral role in various applications, from everyday use to advanced technologies. In the era of machine learning (ML), polymer informatics has become a vital field for efficiently designing and developing polymeric materials. However, the focus of polymer informatics has predominantly centered on single-component polymers, leaving the vast chemical space of polymer blends relatively unexplored. This study employs a high-throughput molecular dynamics (MD) simulation combined with active learning (AL) to uncover polymer blends with enhanced thermal conductivity (TC) compared to the constituent single-component polymers. Initially, the TC of about 600 amorphous single-component polymers and 200 amorphous polymer blends with varying blending ratios are determined through MD simulations. The optimal representation method for polymer blends is identified, which involves a weighted sum approach that extends existing polymer representation from single-component polymers to polymer blends. An AL framework, combining MD simulation and ML, is employed to explore the TC of approximately 550,000 unlabeled polymer blends. The AL framework proves highly effective in accelerating the discovery of high-performance polymer blends for thermal transport. Additionally, we delve into the relationship between TC, radius of gyration (R_g), and hydrogen bonding, highlighting the roles of inter- and intra-chain interactions in thermal transport in amorphous polymer blends. A significant positive association between TC andR_gimprovement and an indirect contribution from H-bond interaction to TC enhancement are revealed through a log-linear model and an odds ratio calculation, emphasizing the impact of increasingR_gand H-bond interactions on enhancing polymer blend TC. 

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