Layer-by-layer (LbL) processing, otherwise known as sequential deposition, is emerging as the most promising strategy for fabrication of active layers in organic photovoltaic (OPV) devices on both laboratory and industrial scales.

Cellulose nanocrystals (CNCs) are becoming a popular option when producing polymer nanocomposites because they are a green alternative to petroleum‐based performance enhancers and provide significant matrix reinforcement at low loadings. DextraCel is a commercial grade CNC with carboxylate surface groups that can be dispersed in water without sonication. These carboxylated CNCs (cCNCs) can be incorporated in situ via seeded semi‐batch emulsion polymerization to produce latexes for adhesive applications. The resulting nanocomposite films exhibit 26x higher peel strength, 4.5x higher tack, and 7.7x higher shear strength relative to base case films. Curiously, adhesives produced from latexes containing cCNCs that do not undergo ultrasonication display greater adhesive property improvements relative to films produced with cCNCs that are ultrasonicated. Atomic force microscopy images reveal that cCNCs have stronger self interactions than their sulfated CNCs counterparts; cCNCs display side‐by‐side and end‐to‐end association in films when they are not ultrasonicated, which increases their “apparent” aspect ratio—an important characteristic attributed to matrix reinforcement. Omitting ultrasonication preserves cCNC‐cCNC interactions that cause them to behave like nanofibers rather than discrete nanocrystals; this allows them to display greater mechanical enhancements, similar to reinforcements provided by nanofibrils, without the technical challenges associated with producing composite latexes with nanofibrils.

Silicon phthalocyanines (SiPc) are showing promise as both ternary additives and non-fullerene acceptors in organic photovoltaics (OPVs) as a result of their ease of synthesis, chemical stability and strong absorption. In this study, bis(3,4,5-trifluorophenoxy) silicon phthalocyanine ((345F)2-SiPc)) and bis(2,4,6-trifluorophenoxy) silicon phthalocyanine ((246F)2-SiPc)) are employed as acceptors in mixed solution/evaporation planar heterojunction (PHJ) devices. The donor layer, either poly(3-hexylthiophene) (P3HT) or poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT), was spin coated followed by the evaporation of the SiPc acceptor thin film. Several different donor/acceptor combinations were investigated in addition to investigations to determine the effect of film thickness on device performance. Finally, the effects of annealing, prior to SiPc deposition, after SiPc deposition, and during SiPc deposition were also investigated. The devices which performed the best were obtained using PCDTBT as the donor, with a 90 nm film of (345F)2-SiPc as the acceptor, followed by thermal annealing at 150 °C for 30 min of the entire mixed solution/evaporation device. An open-circuit voltage (Voc) of 0.88 V and a fill factor (FF) of 0.52 were achieved leading to devices that outperformed corresponding fullerene-based PHJ devices.

Understanding the effect of processing conditions on thin-film morphology is required to develop high-performance organic thin-film electronics such as organic thin-film transistors. Thin films of bis-(pentafluorophenoxy) silicon phthalocyanine (F 10 -SiPc) were evaporated onto surfaces treated with or without octyltrichlorosilane while being held at different substrate temperatures from room temperature to 150 °C. Scanning transmission X-ray microscopy (STXM), performed at various orientations of the linearly polarized monochromatic X-rays, was used to investigate the resulting film morphology. By monitoring the intensity of the π CC * transition from the fluorinated substituent as a function of the polarization angle, we were able to determine the local molecular orientation. Processing the compositional maps enabled the development of structure−property relationships between processing conditions through plane domain sizes and grain boundaries. Atomic force microscopy, which only characterizes the thin-film surface, corroborated the STXM morphology results. This study highlights the potential of STXM to enable a comprehensive characterization across the entire thickness of silicon phthalocyanine thin films and simultaneously prove molecular orientational maps in addition to the morphological features of the domains of the film, not just the surface.

Silicon phthalocyanines (SiPcs) are promising, inexpensive, and easy to synthesize non-fullerene acceptor (NFA) candidates for all-solution sequentially processed layer-by-layer (LbL) organic photovoltaic (OPV) devices. Here, we report the use of bis(tri-n-butylsilyl oxide) SiPc ((3BS) 2 -SiPc) paired with poly(3-hexylthiophene) (P3HT) and poly [(2,6-(4,8-bis(5-(2-ethylhexyl)] (PBDB-T) donors in an LbL OPV structure. Using a direct architecture, P3HT/(3BS) 2 -SiPc LbL devices show power conversion efficiencies (PCEs) up to 3.0%, which is comparable or better than the corresponding bulk heterojunction (BHJ) devices with either (3BS) 2 -SiPc or PC 61 BM. PBDB-T/(3BS) 2 -SiPc LbL devices resulted in PCEs up to 3.3%, with an impressive open-circuit voltage (V oc ) as high as 1.06 V, which is among the highest V oc obtained employing the LbL approach. We also compared devices incorporating vanadium oxide (VOx) or poly(3,4ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as a hole transporting layer and found that VOx modified the donor layer morphology and led to improved V oc . Probing the composition as a function of film layer depths revealed a similar distribution of active material for both BHJ and LbL structures when using (3BS) 2 -SiPc as an NFA. These findings suggest that (3BS) 2 -SiPc is a promising NFA that can be processed using the LbL technique, an inherently easier fabrication methodology for large-area production of OPVs.