Wetting Behavior-Induced Interfacial transmission of Energy and Signal: Materials, Mechanisms, and Applications.

Wetting behaviors can significantly affect the transport of energy and signal (E&S) through vapor, solid, and liquid interfaces, which has prompted increased interest in interfacial science and technology. E&S transmission can be achieved using electricity, light, and heat, which often accompany and interact with each other. Over the past decade, their distinctive transport phenomena during wetting processes have made significant contributions to various domains. However, few studies have analyzed the intricate relationship between wetting behavior and E&S transport. This review summarizes and discusses the mechanisms of electrical, light, and heat transmission at wetting interfaces to elucidate their respective scientific issues, technical characteristics, challenges, commonalities, and potential for technological convergence. The materials, structures, and devices involved in E&S transportation are also analyzed. Particularly, harnessing synergistic advantages in practical applications and constructing advanced, multifunctional, and highly efficient smart systems based on wetted interfaces is the aim to provide strategies.

Empowering Photovoltaic Panel Anti-Icing: Superhydrophobic Organic Composite Coating with In Situ Photothermal and Transparency.

Solar energy is widely used in photovoltaic power generation as a kind of clean energy. However, the liquid film, frosting, and icing on the photovoltaic module seriously limit the efficiency of photovoltaic power generation. We developed a composite coating (Y6-NanoSH) by combining an in situ photothermal and transparent Y6 organic film with a nanosuperhydrophobic material. The Y6-NanoSH coated glass exhibited excellent optical clarity both indoors and outdoors, indicating that the coating holds great promise in anti-icing applications for photovoltaic panels. The Y6-NanoSH coating absorbs very little visible light but instead absorbs in the near-infrared region, thereby emitting heat. When exposed to sunlight, the Y6-NanoSH coated photovoltaic panel raises its surface temperature, inhibiting the growth and accumulation of ice and frost on its surface. This is achieved through a combination of photothermal emission and superhydrophobic repellency, which promotes the evaporation and rolling away of water droplets. This validates our success in developing a photothermal, transparent, and superhydrophobic coating with excellent anti-icing capabilities, suitable for use on photovoltaic panels, as well as potential applications in car windscreens, transmission lines, curtain walls, and weather radomes.

Recombination between Photogenerated and Electrode-Induced Charges Dominates the Fill Factor Losses in Optimized Organic Solar Cells.

Charge extraction in organic solar cells (OSCs) is commonly believed to be limited by bimolecular recombination of photogenerated charges. However, the fill factor of OSCs is usually almost entirely governed by recombination processes that scale with the first order of the light intensity. This linear loss was often interpreted to be a consequence of geminate or trap-assisted recombination. Numerical simulations show that this linear dependence is a direct consequence of the large amount of excess dark charge near the contact. The first-order losses increase with decreasing mobility of minority carriers, and we discuss the impact of several material and device parameters on this loss mechanism. This work highlights that OSCs are especially vulnerable to injected charges as a result of their poor charge transport properties. This implies that dark charges need to be better accounted for when interpreting electro-optical measurements and charge collection based on simple figures of merit.

High Exciton Diffusion Coefficients in Fused Ring Electron Acceptor Films.

Modest exciton diffusion lengths dictate the need for nanostructured bulk heterojunctions in organic photovoltaic (OPV) cells; however, this morphology compromises charge collection. Here, we reveal rapid exciton diffusion in films of a fused-ring electron acceptor that, when blended with a donor, already outperforms fullerene-based OPV cells. Temperature-dependent ultrafast exciton annihilation measurements are used to resolve a quasi-activationless exciton diffusion coefficient of at least 2 × 10-2 cm2/s, substantially exceeding typical organic semiconductors and consistent with the 20-50 nm domain sizes in optimized blends. Enhanced three-dimensional diffusion is shown to arise from molecular and packing factors; the rigid planar molecular structure is associated with low reorganization energy, good transition dipole moment alignment, high chromophore density, and low disorder, all enhancing long-range resonant energy transfer. Relieving exciton diffusion constraints has important implications for OPVs; large, ordered, and pure domains enhance charge separation and transport, and suppress recombination, thereby boosting fill factors. Further enhancements to diffusion lengths may even obviate the need for the bulk heterojunction morphology.

Hidden Structure Ordering Along Backbone of Fused-Ring Electron Acceptors Enhanced by Ternary Bulk Heterojunction.

Fused-ring electron acceptors (FREAs), as a family of non-fullerene (NF) acceptors, have achieved tremendous success in pushing the power conversion efficiency of organic solar cells. Here, the detailed molecular packing motifs of two extensively studied FREAs-ITIC and ITIC-Th are reported. It is revealed for the first time the long-range structure ordering along the backbone direction originated from favored end group π-π stacking. The backbone ordering could be significantly enhanced in the ternary film by the mutual mixing of ITIC and ITIC-Th, which gives rise to an improved in-plane electron mobility and better ternary device performance. The backbone ordering might be a common morphological feature of FREAs, providing explanations to previously observed small open circuit voltage loss and superior performance of FREA-based devices and guiding the future molecular design of high-performance NF acceptors.

Unique Energy Alignments of a Ternary Material System toward High-Performance Organic Photovoltaics.

Incorporating narrow-bandgap near-infrared absorbers as the third component in a donor/acceptor binary blend is a new strategy to improve the power conversion efficiency (PCE) of organic photovoltaics (OPV). However, there are two main restrictions: potential charge recombination in the narrow-gap material and miscompatibility between each component. The optimized design is to employ a third component (structurally similar to the donor or acceptor) with a lowest unoccupied molecular orbital (LUMO) energy level similar to the acceptor and a highest occupied molecular orbital (HOMO) energy level similar to the donor. In this design, enhanced absorption of the active layer and enhanced charge transfer can be realized without breaking the optimized morphology of the active layer. Herein, in order to realize this design, two new narrow-bandgap nonfullerene acceptors with suitable energy levels and chemical structures are designed, synthesized, and employed as the third component in the donor/acceptor binary blend, which boosts the PCE of OPV to 11.6%.

Polymer Solar Cells with 90% External Quantum Efficiency Featuring an Ideal Light- and Charge-Manipulation Layer.

Rapid progress in the power conversion efficiency (PCE) of polymer solar cells (PSEs) is beneficial from the factors that match the irradiated solar spectrum, maximize incident light absorption, and reduce photogenerated charge recombination. To optimize the device efficiency, a nanopatterned ZnO:Al2 O3 composite film is presented as an efficient light- and charge-manipulation layer (LCML). The Al2 O3 shells on the ZnO nanoparticles offer the passivation effect that allows optimal electron collection by suppressing charge-recombination loss. Both the increased refractive index and the patterned deterministic aperiodic nanostructure in the ZnO:Al2 O3 LCML cause broadband light harvesting. Highly efficient single-junction PSCs for different binary blends are obtained with a peak external quantum efficiency of up to 90%, showing certified PCEs of 9.69% and 13.03% for a fullerene blend of PTB7:PC71 BM and a nonfullerene blend, FTAZ:IDIC, respectively. Because of the substantial increase in efficiency, this method unlocks the full potential of the ZnO:Al2 O3 LCML toward future photovoltaic applications.

Ternary System with Controlled Structure: A New Strategy toward Efficient Organic Photovoltaics.

Recently, a new type of active layer with a ternary system has been developed to further enhance the performance of binary system organic photovoltaics (OPV). In the ternary OPV, almost all active layers are formed by simple ternary blend in solution, which eventually leads to the disordered bulk heterojunction (BHJ) structure after a spin-coating process. There are two main restrictions in this disordered BHJ structure to obtain higher performance OPV. One is the isolated second donor or acceptor domains. The other is the invalid metal-semiconductor contact. Herein, the concept and design of donor/acceptor/acceptor ternary OPV with more controlled structure (C-ternary) is reported. The C-ternary OPV is fabricated by a sequential solution process, in which the second acceptor and donor/acceptor binary blend are sequentially spin-coated. After the device optimization, the power conversion efficiencies (PCEs) of all OPV with C-ternary are enhanced by 14-21% relative to those with the simple ternary blend; the best PCEs are 10.7 and 11.0% for fullerene-based and fullerene-free solar cells, respectively. Moreover, the averaged PCE value of 10.4% for fullerene-free solar cell measured in this study is in great agreement with the certified one of 10.32% obtained from Newport Corporation.

Naphthodithiophene-Based Nonfullerene Acceptor for High-Performance Organic Photovoltaics: Effect of Extended Conjugation.

Naphtho[1,2-b:5,6-b']dithiophene is extended to a fused octacyclic building block, which is end capped by strong electron-withdrawing 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile to yield a fused-ring electron acceptor (IOIC2) for organic solar cells (OSCs). Relative to naphthalene-based IHIC2, naphthodithiophene-based IOIC2 with a larger π-conjugation and a stronger electron-donating core shows a higher lowest unoccupied molecular orbital energy level (IOIC2: -3.78 eV vs IHIC2: -3.86 eV), broader absorption with a smaller optical bandgap (IOIC2: 1.55 eV vs IHIC2: 1.66 eV), and a higher electron mobility (IOIC2: 1.0 × 10-3 cm2 V-1 s-1 vs IHIC2: 5.0 × 10-4 cm2 V-1 s-1 ). Thus, IOIC2-based OSCs show higher values in open-circuit voltage, short-circuit current density, fill factor, and thereby much higher power conversion efficiency (PCE) values than those of the IHIC2-based counterpart. In particular, as-cast OSCs based on FTAZ: IOIC2 yield PCEs of up to 11.2%, higher than that of the control devices based on FTAZ: IHIC2 (7.45%). Furthermore, by using 0.2% 1,8-diiodooctane as the processing additive, a PCE of 12.3% is achieved from the FTAZ:IOIC2-based devices, higher than that of the FTAZ:IHIC2-based devices (7.31%). These results indicate that incorporating extended conjugation into the electron-donating fused-ring units in nonfullerene acceptors is a promising strategy for designing high-performance electron acceptors.

Mapping Polymer Donors toward High-Efficiency Fullerene Free Organic Solar Cells.

Five polymer donors with distinct chemical structures and different electronic properties are surveyed in a planar and narrow-bandgap fused-ring electron acceptor (IDIC)-based organic solar cells, which exhibit power conversion efficiencies of up to 11%.

A Facile Planar Fused-Ring Electron Acceptor for As-Cast Polymer Solar Cells with 8.71% Efficiency.

A planar fused-ring electron acceptor (IC-C6IDT-IC) based on indacenodithiophene is designed and synthesized. IC-C6IDT-IC shows strong absorption in 500-800 nm with extinction coefficient of up to 2.4 × 10(5) M(-1) cm(-1) and high electron mobility of 1.1 × 10(-3) cm(2) V(-1) s(-1). The as-cast polymer solar cells based on IC-C6IDT-IC without additional treatments exhibit power conversion efficiencies of up to 8.71%.