Facile external treatment for efficient nanoscale morphology control of polymer solar cells using a gas-assisted spray method

• Published in: Journal of materials chemistry 2011-01, Vol.21 (12), p.4457-4464
• Main Authors: Park, Hye-Yun, Kim, Kyungkon, Kim, Dong Young, Choi, Si-Kyung, Jo, Seong Mu, Jang, Sung-Yeon
• Format: Article
• Language: English
• Subjects: Annealing; Devices; Morphology; Nanocomposites; Nanomaterials; Nanostructure; Sprayers; Sprays
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/c0jm03899g

A facile and effective treatment method for controlling the morphology of bulk heterojunction (BHJ) structured polymer-based solar cells (PSCs) using a gas-assisted spray (g-spray) technique was demonstrated. High-efficiency BHJ-PSCs were fabricated using a g-spray method that can be adapted to large-scale high-throughput continuous production, and the bulk film morphology and internal nanomorphology of the active layers were well manipulated using a sprayed solvent overlayer (SSO) treatment. The efficient nanomorphology evolution, which is a prerequisite for obtaining high performance BHJ-PSCs, was confirmed by X-ray diffraction, UV-Vis, photoluminescence, and transmission electron microscopy analysis. The SSO treatment was a simple and rapid process that could be carried out at room temperature, unlike conventional external treatment (ET) methods such as solvent- or thermal-assisted treatment, which typically require a prolonged time (1 h) or relatively high temperature (110 [degree]C). After SSO treatment, the PSC performance was enhanced remarkably. The power conversion efficiency (PCE) of the g-sprayed PSCs after SSO treatment was 2.99%, which is higher than that of a solvent vapor treated device (2.42%) and thermally annealed devices (2.61%). Further optimization of the nanomorphology was achieved by sequentially developing P3HT and PCBM. By combining thermal annealing with the SSO treatment, the P3HT/PCBM interfacial area could be enhanced; this enhancement was induced by the PCBM diffusion into the space among pre-assembled P3HT nanofibrils, which in turn promoted their bi-continuity. This means of sequential nanomorphology development further enhanced the PCE (3.35%), which was higher than the other reported values for PSCs using spray methods. Considering that the SSO treatment is a facile room temperature process that requires a short time, these results suggest that the g-spray method can be successfully applied to the continuous production of PSCs.