Abstract
Solution-processed flexible organic optoelectronic devices have great potential as low-cost organic photovoltaics for energy harvesting, and in organic light-emitting diodes as a lighting source. However, a major challenge for improving device performance and stability is the different interfacial characteristics of the hydrophobic organic layers and hydrophilic transparent electrodes, particularly for flexible devices. Surface wetting controlled interfacial engineering can provide a useful method to develop highly efficient flexible organic devices. Here, an unsaturated fatty acid-modified ethoxylated polyethyleneimine organic interfacial layer is designed, which is hydrophobic or hydrophilic on different interfaces. This interlayer results in a power conversion efficiency of 10.57% for rigid and 9.04% for flexible photovoltaic devices. Furthermore, the long-term air storage stability for 250 h is substantially improved, retaining 87.75% efficiency without encapsulation, due to the wettability driven improvement of the optical and electronic properties of the cathode interfacial layer. The performance of organic light emitting diodes also benefitted from the interlayer. This study provides a strategy to simultaneously improve efficiency and stability by controlling the wettability of the interfacial layer.
Highlights
Solution-processed flexible organic optoelectronic devices have great potential as low-cost organic photovoltaics for energy harvesting, and in organic light-emitting diodes as a lighting source
A higher hydrophobicity is observed on the smooth LA-polyethylenimine 80% ethoxylated (PEIE) film surface (Fig. 1d, e), which was previously treated by a linoleic fatty acid
According to the contact angle analysis, the LA-PEIE cathode interfacial layers (CILs) became hydrophilic at the bottom surface facing the indium tin oxide (ITO) layer and hydrophobic at the top surface facing the photoactive layer
Summary
Solution-processed flexible organic optoelectronic devices have great potential as low-cost organic photovoltaics for energy harvesting, and in organic light-emitting diodes as a lighting source. An unsaturated fatty acid-modified ethoxylated polyethyleneimine organic interfacial layer is designed, which is hydrophobic or hydrophilic on different interfaces This interlayer results in a power conversion efficiency of 10.57% for rigid and 9.04% for flexible photovoltaic devices. 1234567890():,; Over the past few decades, organic semiconductor optoelectronic devices, such as organic photovoltaics (OPVs) and organic light-emitting diodes (OLEDs) have garnered considerable attention owing to their remarkable intrinsic properties These properties include solution processability, good mechanical flexibility, and easy and low-cost manufacturing (printing or roll-to-roll fabrication) techniques[1,2,3,4,5,6,7]. The electron transport or material properties of the electron injection layer are important for extracting or injecting electrons while blocking hole transport, which is more effective when using rigid substrates or high-temperature manufacturing processes Among these materials, polyethylenimine 80% ethoxylated (PEIE), a low-cost commercial polyelectrolyte, has been extensively used for fabricating flexible optoelectronic devices. From the reported studies, the wetting properties at the electrode/active layer interface is not yet intensely investigated
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