Producing p-Doped Surface for Hole Transporting Layer-Free Nonfullerene Organic Solar Cells.

Hole transporting layer-free organic solar cells with simplified device structures are desirable for their mass production. In this work, a p-dopant of organic molybdenum peroxide (OMP) to dope nonfullerene active layers to produce p-doped surface on the active layer is adopted. The OMP can effectively dope widely used polymer donors of nonfullerene organic solar cells, i.e., PTB7-Th, PBDB-T, and even PBDB-T-2F that has a very deep highest occupied molecular orbital (HOMO) energy level of -5.47 eV. The doping mechanism lies in the strong oxidizing property of peroxide groups of the OMP leading to superior doping properties. In the end, hole transporting layer-free nonfullerene organic solar cells with the device structure of ITO/PEI-Zn/PBDB-T-2F:IT-4F/Ag are fabricated. The cells show a power conversion efficiency of 12.2% and good thermal stability.

Ultrathin and Efficient Organic Photovoltaics with Enhanced Air Stability by Suppression of Zinc Element Diffusion.

Ultrathin (thickness less than 10 µm) organic photovoltaics (OPVs) can be applied to power soft robotics and wearable electronics. In addition to high power conversion efficiency, stability under various environmental stresses is crucial for the application of ultrathin OPVs. In this study, the authors realize highly air-stable and ultrathin (≈3 µm) OPVs that possess high efficiency (15.8%) and an outstanding power-per-weight ratio of 33.8 W g-1 . Dynamic secondary-ion mass spectrometry is used to identify Zn diffusion from the electron transport layer zinc oxide (ZnO) to the interface of photoactive layer; this diffusion results in the degradation of the ultrathin OPVs in air. The suppression of the Zn diffusion by a chelating strategy results in stable ultrathin OPVs that maintain 89.6% of their initial efficiency after storage for 1574 h in air at room temperature under dark conditions and 92.4% of their initial efficiency after annealing for 172 h at 85 °C in air under dark conditions. The lightweight and stable OPVs also possess excellent deformability with 87.3% retention of the initial performance after 5000 cycles of a compressing-stretching test with 33% compression.

54 cm2 Large-Area Flexible Organic Solar Modules with Efficiency Above 13.

Development of large-area flexible organic solar cells (OSCs) is highly desirable for their practical applications. However, the efficiency of the large-area flexible OSCs severely lags behind small-area devices. Here, efficient large-area flexible single cells with power conversion efficiency (PCE) of 13.1% and 12.6% for areas of 6 and 10 cm2 , and flexible modules with a PCE of 13.2% (54 cm2 ) based on poly(ethylene terephthalate)/Ag grid/silver nanowires (AgNWs):zinc-chelated polyethylenimine (PEI-Zn) composite electrodes are reported. The solution-processed flexible transparent electrode of AgNWs:PEI-Zn shows low surface roughness and good optoelectronic and mechanical properties. PEI-Zn is conductive and optically transparent. It can adhere to and wrap the AgNWs under electrostatic interaction between the negatively charged surface (AgNWs) and positively charged protonated amine groups (in PEI-Zn). It wraps the AgNWs networks and fills the void space to achieve a smooth surface. The flexible electrode is validated in both flexible OSCs and flexible quantum-dots light-emitting diodes (QLEDs). Small-area flexible OSCs show a PCE of 16.1%, and flexible QLEDs show an external quantum efficiency of 13.3%. In the end, a flexible module is demonstrated to charge a mobile phone as a flexible power source (shown in Video S1, Supporting Information).

Robust metal ion-chelated polymer interfacial layer for ultraflexible non-fullerene organic solar cells.

Achieving high power conversion efficiency and good mechanical robustness is still challenging for the ultraflexible organic solar cells. Interlayers simultaneously having good mechanical robustness and good chemical compatibility with the active layer are highly desirable. In this work, we present an interlayer of Zn2+-chelated polyethylenimine (denoted as PEI-Zn), which can endure a maximum bending strain over twice as high as that of ZnO and is chemically compatible with the recently emerging efficient nonfullerene active layers. On 1.3 µm polyethylene naphthalate substrates, ultraflexible nonfullerene solar cells with the PEI-Zn interlayer display a power conversion efficiency of 12.3% on PEDOT:PSS electrodes and 15.0% on AgNWs electrodes. Furthermore, the ultraflexible cells show nearly unchanged power conversion efficiency during 100 continuous compression-flat deformation cycles with a compression ratio of 45%. At the end, the ultraflexible cell is demonstrated to be attached onto the finger joint and displays reversible current output during the finger bending-spreading.

Flexible All-Solution-Processed Organic Solar Cells with High-Performance Nonfullerene Active Layers.

All-solution-processed organic solar cells (from the bottom substrate to the top electrode) are highly desirable for low-cost and ubiquitous applications. However, it is still challenging to fabricate efficient all-solution-processed organic solar cells with a high-performance nonfullerene (NF) active layer. Issues of charge extraction and wetting are persistent at the interface between the nonfullerene active layer and the printable top electrode (PEDOT:PSS). In this work, efficient all-solution-processed NF organic solar cells (from the bottom substrate to the top electrode) are reported via the adoption of a layer of hydrogen molybdenum bronze (HX MoO3 ) between the active layer and the PEDOT:PSS. The dual functions of HX MoO3 include: 1) its deep Fermi level of -5.44 eV can effectively extract holes from the active layer; and 2) the wetting issues of the PEDOT:PSS on the hydrophobic surface of the NF active layer can be solved. Importantly, fine control of the HX MoO3 composition during the synthesis is critical in obtaining processing orthogonality between HX MoO3 and the PEDOT:PSS. Flexible all-solution-processed NF organic solar cells with power conversion efficiencies of 11.9% and 10.3% are obtained for solar cells with an area of 0.04 and 1 cm2 , respectively.

Detection improvement of laser-induced breakdown spectroscopy using the flame generated from alcohol-solution mixtures.

It has been proved that the detection of laser-induced breakdown spectroscopy (LIBS) could be improved by the flame. In this work, we applied flame enhanced LIBS for the detection of elements in water, while the flame was generated from the mixture of alcohol and aqueous solution. In the measurements, the flame is functioned as an assistance to enhance the LIBS detection, and also worked as a sampling way for the solution. The obtained results indicate that the detection of manganese, calcium, lithium and magnesium were significantly improved by the proposed method. It is found that the flame actually forms an environment for the laser-induced plasma to have higher temperature and lower electron density, as comparing with the plasma underwater. With the method, the quantitative analysis was tried out for the element of manganese, and the internal reference of calcium was used. It is interesting to find that, when mixing with the calcium, the minimum detectable concentration of manganese could be lowered and the intensity was greatly increased. According to the result, it is suggested that the proposed method might be a practical way for liquid detection of LIBS because of the simplicity and the effectiveness.

Flexible and Transparent Organic-Inorganic Hybrid Thermoelectric Modules.

Light-weight, mechanically flexible, transparent thermoelectric modules are promising as portable and easy-to-integrate energy sources. Here, we demonstrate flexible, transparent thermoelectric modules by using a conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the p-type leg and indium tin oxide (ITO)-PEDOT:PSS as the n-type leg. Main observations include the following: (1) the bilayer combination of ITO-PEDOT:PSS (PEDOT:PSS coated on top of the ITO) displays a negative Seebeck coefficient ( S) and the value is similar to that of the ITO single layer; (2) the S value of the ITO-PEDOT:PSS is almost not dependent on the area ratio of the stacked PEDOT:PSS and ITO; and (3) the conducting polymer PEDOT:PSS deposition on top of ITO helps the ITO not to generate cracks during bending, which enhances the mechanical flexibility of the ITO. On the basis of these observations, thermoelectric modules with eight pairs of junctions are fabricated and the thermoelectric modules' Δ V/Δ T (modules' generated thermovoltage per temperature difference) is nearly the addition of S values of all legs. Thermoelectric modules show good mechanical flexibility and air stability. Applications of thermoelectric modules have also been demonstrated to produce thermovoltage via the temperature difference produced by a human hand or warm water.

Free-Standing Conducting Polymer Films for High-Performance Energy Devices.

Thick, uniform, easily processed, highly conductive polymer films are desirable as electrodes for solar cells as well as polymer capacitors. Here, a novel scalable strategy is developed to prepare highly conductive thick poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (HCT-PEDOT:PSS) films with layered structure that display a conductivity of 1400 S cm(-1) and a low sheet resistance of 0.59 ohm sq(-1). Organic solar cells with laminated HCT-PEDOT:PSS exhibit a performance comparable to the reference devices with vacuum-deposited Ag top electrodes. More importantly, the HCT-PEDOT:PSS film delivers a specific capacitance of 120 F g(-1) at a current density of 0.4 A g(-1). All-solid-state flexible symmetric supercapacitors with the HCT-PEDOT:PSS films display a high volumetric energy density of 6.80 mWh cm(-3) at a power density of 100 mW cm(-3) and 3.15 mWh cm(-3) at a very high power density of 16160 mW cm(-3) that outperforms previous reported solid-state supercapacitors based on PEDOT materials.