We report a novel light management approach based on solution-processed nanowire (NW) coating for enhancing organic solar cell efficiency. A titanium dioxide (TiO2) NW dispersion was produced by electrospinning. The coatings with various coverage fractions were fabricated by a simple solution casting of a TiO2 NW dispersion. Reduced reflectivity was observed for the NW-coated glass slide. The bulk-heterojunction organic solar cells with the NW coating showed improved power conversion efficiencies (PCEs) due to their antireflection and light trapping effects in the active layer. In addition, the PCE of the cell with the NW coating was improved compared with that without the NW coating for incident angles above 70° (increased by a maximum of 51.6% at an incident angle of 85°). These results indicate that solution-processed NW coating is a promising light management approach easily scalable and applicable to a wide range of devices, including solar cells. 1. Introduction Organic solar cells, which can be fabricated by simple processing techniques, are being intensely studied because of their potential to enable the mass production of flexible and low-cost devices [1, 2]. Most of the attention has been focused on solution-processed polymer bulk-heterojunction (BHJ) solar cells [3, 4]. A combination of polymer design, morphology control, structural insight, and device engineering has led to power conversion efficiencies (PCEs) reaching the 6–8% range for conjugated polymer/fullerene blends [5, 6]. However, the BHJ morphology, a bicontinuous, nanoscaled, phase-separated donor and acceptor components of organic solar cells, has an intrinsic conflict between the optical and the electronic length scales: the BHJ layer of a few hundred nm can achieve complete light absorption, but the exciton-diffusion length is only around 20？nm [7, 8]. To resolve this conflict, versatile and scalable light management techniques are strongly required for reduction of the BHJ film thickness with low-loss optical absorption [9, 10]. Here we report a novel light management approach based on a solution-processed nanowire (NW) coating for enhancing organic solar cell efficiency. For light management, in particular for antireflection coatings or light trapping in the BHJ layer, nanostructures play a crucial role [7–9]. However, versatile and scalable fabrication methods of nanostructures are limited. A number of approaches have been actively explored to synthesize one-dimensional (1-D) nanomaterials [11]. Electrospinning has also been explored as a fast and efficient top-down process
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