Cathode interlayers (CILs) in organic photovoltaics (OPVs) are actively being researched as they are critical for device stability and performance. Herein, N‐annulated perylene diimide with a 2‐ethyl‐hexyl side chain (PDIN‐EH) is demonstrated, which is facile to synthesize as compared with conventional CILs such as PFN‐Br, exhibits solubility, and subsequent processability from ethanol. The PDIN‐EH is evaluated as a CIL in an air‐processed, slot‐die coated OPV consisting of PEDOT:PSS as the hole transport layer, PM6:Y6C12 as the bulk heterojunction, and top silver cathode electrode. All the organic layers are slot‐die coated from green solvents and devices achieve a power convention efficiency of more than 12%, a result that is among the best reported under ambient conditions for printed OPVs. Microscopy images reveal that the PDIN‐EH affords smooth film formation when slot‐die coated on top of PM6:Y6C12 bulk heterojunction for an improved contact with the Ag electrode. Furthermore, the fabrication of large‐area OPV modules on glass and flexible (polyethylene terephthalate) substrates is successfully demonstrated, with five cells connected in series achieving efficiency over 7% and open‐circuit voltage over 3.5 V. Herein, useful guidelines for achieving fully printed organic electronic devices from green solvents at a potential industrial scale are provided.
We have investigated an effective and a single-step chemical vapor deposition (CVD) method to achieve conformal visible poly-dichloro-para-xylylene (parylene C) film for light extraction enhancement in bottom-emitting organic light-emitting diodes (OLEDs) at room temperature. We report that sublimed parylene dimers pyrolyzed between 400 °C and 500 °C resulted in visible parylene films with tunable transmittance and haze, exhibiting light scattering properties due to the formation of uniformly distributed dimer crystals. We achieved a novel conformal visible parylene film with total transmittance and high haze of 79.5% and 93.6%, respectively. It is observed that the outcoupling efficiency of the OLEDs employing the visible parylene film is enhanced up to 45.8%. Additionally, the OLED with the visible parylene light extraction film shows limited angle-dependency of emission spectrum over viewing angles. The single-step room temperature fabrication process of this conformal outcoupling film paves the way to achieving commercial high-performance OLEDs.
Solution-processable organic solar cells (OSCs) have the potential to offer a source of low-cost renewable energy with low-energyintensive processing, have lightweight and flexible features, and power conversion efficiency (PCE) values of 19%. [1,2] The most efficient OSC devices are based on the bulk heterojunction (BHJ) structure composed of nanoscale intermixed continuous networks of an electron-donating conjugated polymer and a nonfullerene electron-accepting small molecule, together with anode and cathode interlayers (CILs) to improve charge carrier transport and collection in the device. [3,4] In bottom-anode top-cathode device configuration, PEDOT:PSS is the most common anode interlayer, which is deposited on top of the indium tin oxide (ITO) transparent electrode. In this configuration, the CIL would therefore be deposited on top of the organic BHJ to modify the electrode work function, such that OSC device performance would be increased as a result of the energy barrier between the metal electrode and the active layer being decreased. [5][6][7][8] To date, organic compounds have been widely applied as interlayers, and benchmark CILs for conventional OSC structure utilize the PFN-Br polymer [9] and small molecules based on perylene diimide (PDI) derivatives, such as those with polar amino N-oxide groups (PDINO) [10] or aliphatic amine groups (PDINN). [11] The polar groups endow the molecules with good solubility in methanol, a processing solvent that does not destroy the underlying organic photoactive layer. [4] In terms of better reproducibility, reduced synthetic steps, and well-defined structures, small-molecule interlayers exhibit intrinsic advantages over polymeric materials, which position PDI-based CILs as excellent candidates for future industrial applications of OSCs. [12,13] PDIs also have high electron mobility, strong optical absorption, suitable energy levels, and stability. [14] In addition, they can be easily functionalized to tune the work function of the electrode. [13,15] Through chemical modification, the electronic and morphological features of the applied PDI in the interlayer film can be adjusted to deliver better performance in the OSC device. Recently, some works featured the use of bay-substituted PDIs as CILs in OSCs. Wang et al. reported the synthesis of three bay-substituted PDIs and their application as CILs in OSCs, with performance of 16% when combined with PM6:Y6. [16] Our group also reported the use of PDI compounds containing NH groups functionalized at the bay region as an interlayer in OSCs, slot die coated from ethanol, with device performance above 10%. [17] Here, we present the application of a series of bay positionsubstituted N-annulated PDI derivatives as interlayers for OSCs. These N-PDIs possess well-defined structures and good film-forming ability on top of the organic photoactive layer,
This study proposes front colored glass for building integrated photovoltaic (BIPV) systems based on multi-layered derivatives of glass/MoO3/Al2O3 with a process technology developed to realize it. Molybdenum oxide (MoO3) and aluminum oxide (Al2O3) layers are selected as suitable candidates to achieve thin multi-layer color films, owing to the large difference in their refractive indices. We first investigated from a simulation based on wave optics that the glass/MoO3/Al2O3 multi-layer type offers more color design freedom and a cheaper fabrication process when compared to the glass/Al2O3/MoO3 multi-layer type. Based on the simulation, bright blue and green were primarily fabricated on glass. It is further demonstrated that brighter colors, such as yellow and pink, can be achieved secondarily with glass/MoO3/Al2O3/MoO3 due to enhanced multi-interfacial reflections. The fabricated color glasses showed the desired optical properties with a maximum transmittance exceeding 80%. This technology exhibits promising potential in commercial BIPV system applications.
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