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A novel 2D benzodifuran (BDF)-based copolymer (PBDF-T1) is synthesized. Polymer solar cells fabricated with PBDF-T1 show high power conversion efficiency of 9.43% and fill factor of 77.4%, which is higher than the performance of its benzothiophene (BDT) counterpart (PBDT-T1). These results provide important progress for BDF-based copolymers and demonstrate that BDF-based copolymers can be competitive with the well-studied BDT counterparts via molecular structure design and device optimization.

Highly efficient large-area organic solar cells (OSCs) with power conversion efficiency up to 7.09%, and device area of 4 cm² are demonstrated on flexible substrates. A conductance- or thickness-gradient ultra-thin Ag-based transparent electrode is developed to better balance the light trapping and energy loss, owing to the inhomogeneous energy-loss density on the large OSC sheet.

An optimum amount of lead bromide (1%) can enhance the power conversion efficiency of CH₃NH₃PbI_3−xBr_x (where x ≈ 0) devices from 14.7% to 16.9% without altering the bandgap of the perovskite material.

Two medium-bandgap polymers composed of benzo[1,2-b:4,5-b′]dithiohpene and 2,1,3-benzothiadiazole with 6-octyl-thieno[3,2-b]thiophene as a π-bridge unit are synthesized and their photovoltaic properties are analyzed. The two polymers have deep highest occupied molecular orbital energy levels, high crystallinity, optimal bulk-heterojunction morphology, and efficient charge transport, resulting in a power conversion efficiency of as high as 9.44% for a single-junction polymer solar-cell device.

A series of conjugated polymers using naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole and benzodithiophene alternating backbone is synthesized to investigate the effect of side chain substitution on conjugated donor–acceptor polymer on electronic, morphological, and photovoltaic properties. It is found that light absorption and frontier energy levels of the resultant polymers are strongly affected by the side chains. The thin film morphology, crystal structure, crystallinity, and orientation also depend on the side chains; the side chain type affects more in the π–π stacking direction, while the side chain density plays a significant role in the lamellar packing direction. The thickness of the active layer also influences the performance of the solar cells with some materials showing enhanced performance with thicker active layers. The best solar cell device in this study has power conversion efficiencies of 8.14%, among the highest in materials of similar structure.

Systematic side chain engineering based on naphtho [1,2-c:5,6-c]bis[1,2,5]thiadiazole–benzodithiophene copolymer is carried out; a detailed structural analysis of these polymers in the active layer of organic solar cells is performed to elucidate the influence of side chain on their crystalline, morphological, and photovoltaic properties.

A key issue for perovskite solar cells is the stability of perovskite materials due to moisture effects under ambient conditions, although their efficiency is improved constantly. Herein, an improved CH₃NH₃PbI_3−xCl_x perovskite quality is demonstrated with good crystallization and stability by using water as an additive during crystal perovskite growth. Incorporating suitable water additives in N,N-dimethylformamide (DMF) leads to controllable growth of perovskites due to the lower boiling point and the higher vapor pressure of water compared with DMF. In addition, CH₃NH₃PbI_3−xCl_x · nH₂O hydrated perovskites, which can be resistant to the corrosion by water molecules to some extent, are assumed to be generated during the annealing process. Accordingly, water additive based perovskite solar cells present a high power conversion efficiency of 16.06% and improved cell stability under ambient conditions compared with the references. The findings in this work provide a route to control the growth of crystal perovskites and a clue to improve the stability of organic–inorganic halide perovskites.

Water additive is incorporated into the perovskite precursor solution to control the oriented growth of crystal perovskites and improve the stability of perovskite solar cells. As a result, a power conversion efficiency of 16.06% and an improved cell stability under ambient conditions are achieved.

Stimuli-responsive gene delivery systems maximize therapeutic efficacy by controlling the cytosolic conveyance and rate of effective gene release. We present herein a hybrid nanocomposite composed of a 2D nanomaterial, MoS₂, modified by attaching two polymers (polyethylenimine (PEI) and polyethylenglycol (PEG)) via disulfide bonds. This MoS₂–PEI–PEG nanocomposite interacts with DNA by electrostatic interaction, and accordingly forms a nanosized complex with high stability. Photothermal conversion of MoS₂ nanosheet is employed in order to induce photothermally triggered endosomal escape upon the near infrared light irradiation. After endosomal escape, polymers are detached from the MoS₂ nanosheet by the intracellular reducing agent, glutathione (GSH), resulting in effective gene release from the nanocomposite. This sequential process initiated by external and internal stimuli remarkably enhances gene delivery efficiency by effective endosomal escape and gene release without severe cytotoxicity. Our rationally designed MoS₂ nanocomposite provides a spatiotemporally controllable platform to deliver genetic material into cells.

Single-layered MoS₂–PEI–PEG nanocomposites provide an externally and internally controllable platform for effective gene transfection. Local heat generated from MoS₂ enables the endosomal escape of polyplexes, and sequentially intracellular redox environment governed by GSH triggers the effective DNA release, leading to high gene transfection.

The photoluminescence, transmittance, charge-carrier recombination dynamics, mobility, and diffusion length of CH₃NH₃PbI₃ are investigated in the temperature range from 8 to 370 K. Profound changes in the optoelectronic properties of this prototypical photovoltaic material are observed across the two structural phase transitions occurring at 160 and 310 K. Drude-like terahertz photoconductivity spectra at all temperatures above 80 K suggest that charge localization effects are absent in this range. The monomolecular charge-carrier recombination rate generally increases with rising temperature, indicating a mechanism dominated by ionized impurity mediated recombination. Deduced activation energies E_a associated with ionization are found to increase markedly from the room-temperature tetragonal (E_a ≈ 20 meV) to the higher-temperature cubic (E_a ≈ 200 meV) phase adopted above 310 K. Conversely, the bimolecular rate constant decreases with rising temperature as charge-carrier mobility declines, while the Auger rate constant is highly phase specific, suggesting a strong dependence on electronic band structure. The charge-carrier diffusion length gradually decreases with rising temperature from about 3 μm at −93 °C to 1.2 μm at 67 °C but remains well above the optical absorption depth in the visible spectrum. These results demonstrate that there are no fundamental obstacles to the operation of cells based on CH₃NH₃PbI₃ under typical field conditions.

The photoconductivity in CH₃NH₃PbI₃ thin films is investigated from 8 to 370 K across three structural phases. Analysis of the charge-carrier recombination dynamics reveals a variety of starkly differing recombination mechanisms. Evidence of charge-carrier localization is observed only at low temperature. High charge mobility and diffusion length are maintained at high temperature beyond the tetragonal-to-cubic phase transition at ≈310 K.

Layered 2D materials serve as a new class of substrates for templated synthesis of various nanomaterials even with highly dissimilar crystal structures; thus overcoming the lattice constraints of conventional epitaxial processes. Here, molybdenum disulfide (MoS₂) is used as a prototypical model substrate for oriented growth of in-plane Au nanowires (NWs) despite the nearly 8% lattice mismatch between MoS₂ and Au. Au NWs on the MoS₂ surface are oriented along three symmetrically equivalent directions within the substrate arising from the strong Au–S binding that templates the oriented growth. The kinetics of the growth process are explored through experiments and modeling. Strong charge transfer is observed between Au NWs and MoS₂, resulting in degenerate p-doping of MoS₂.

Au nanowires (NWs) are laterally grown on a 2D material, molybdenum disulfide (MoS₂) via treatment with AuCl₃ solution. The Au NWs are oriented on the MoS₂ surface with C3 symmetry, reflecting the surface of the MoS₂ crystal plane. Analysis of the electrical characteristics indicates a surface charge transfer reaction between AuCl₃ and MoS₂, showing p-type doping up to the degenerate limit.

Ternary-blend polymer solar cells can be effectively improved by incorporating a heterostructured near-IR dye, which has a hexyl group compatible with the polymer and a benzyl group compatible with the fullerene. Because of the compatibility with both materials, the heterostructured dye can be loaded up to 15 wt% and hence can boost the photocurrent generation by 30%.

An optimized configuration of TiO₂ microspheres in photoanodes is of great importance to prepare highly efficient dye-sensitized solar cells (DSSCs). In this work, TiO₂ microspheres with tunable diameter, pore size, and porosity are synthesized by subtly adjusting the synthesizing conditions, including ratios of deionized water, ammonia, and ethanol, respectively. TiO₂ microspheres are obtained with large pore sizes and a high porosity without sacrificing specific surface areas. In addition, the effect of their porosity and pore size on the performance of DSSCs is investigated. As confirmed by the dye-loading ability and electrolyte diffusion resistance, the large mesopores and the high porosity of the TiO₂ microspheres can improve dye adsorption and facilitate electrolyte diffusion, giving rise to a high light-harvesting and electron collection efficiency. Consequently, the highest photocurrent of 19.21 mA cm⁻² and a power conversion efficiency of 9.98% are obtained by using the TiO₂ microspheres with the highest porosity, compared with a 9.29% efficiency demonstrated by the lowest porosity (an improvement of 7.4%). By modifying the interconnection and the external pores of the microspheres photoanode, a high efficiency of 11.67% is achieved for a DSSC based on the most potent TiO₂ microspheres.

Mesoporous TiO₂ microspheres with controllable diameter, pore size, and porosity are synthesized. The porosity of the microspheres can be easily tuned without sacrificing the specific surface area by adjusting the content of ethanol. The large porosity of microspheres shows an abundant dye adsorption, rapid dye regeneration, and sufficient electrolyte diffusion, resulting in a higher efficiency of 11.67%.

This work focuses on developing diketopyrrolopyrrole (DPP)-based small molecular nonfullerene acceptors for bulk heterojunction (BHJ) organic solar cells. The materials, SF-DPPs, have an X-shaped geometry arising from four DPP units attached to a spirobifluorene (SF) center. The spiro-dimer of DPP-fluorene-DPP is highly twisted, which suppresses strong intermolecular aggregation. Branched 2-ethylhexyl (EH), linear n-octyl (C8), and n-dodecyl (C12) alkyl sides are chosen as substituents to functionalize the N,N-positions of the DPP moiety to tune molecular interactions. SF-DPPEH, the best candidate in SF-DPPs family, when blended with poly(3-hexylthiophene) (P3HT) showed a moderate crystallinity and gives a J_sc of 6.96 mA cm⁻², V_oc of 1.10 V, a fill factor of 47.5%, and a power conversion efficiency of 3.63%. However, SF-DPPC8 and SF-DPPC12 exhibit lower crystallinity in their BHJ blends, which is responsible for their reduced J_sc. Coupling DPP units with SF using an acetylene bridge yields SF-A-DPP molecules. Such a small modification leads to drastically different morphological features and far inferior device performance. These observations demonstrate a solid structure–property relationship by topology control and material design. This work offers a new molecular design approach to develop efficient small molecule nonfullerene acceptors.

A series of spiro-diketopyrrolopyrroles-based nonfullerene acceptors with X-shapes is developed. The substituted alkyl side chains on the acceptors can significantly tailor their crystallinity and bulk heterojunction film morphology. When paring these acceptors with poly(3-hexylthiophene), a dramatic variation of power conversion efficiency from 1.42% to 3.63% is observed.