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Performance Optimization of Polymer Solar Cells Using Electrostatically Sprayed Photoactive Layers

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Abstract

Polymer solar cells (PSCs) are fabricated using a novel film deposition method, the electrostatic spray (e-spray) technique. Stable atomization and uniform deposition of the polymer blend by e-spray are achieved by manipulating the solution concentration, the solvent composition, and the electric field. The performance of PSCs is primarily influenced by the inherent film morphology of the e-sprayed polymer-blend active layers, which is significantly different from that of the conventional films that are formed using the spin-coating (SC) method. The intrinsically formed interfacial boundaries between the e-sprayed blend pancakes resist charge transport, which unfavorably influences device efficiency. The internal series resistance (RS) of the PSCs that are formed using the e-spray method (e-spray-PSC) is significantly reduced by a solvent vapor soaking (SVS) treatment in addition to the conventional thermodynamic nanomorphology controls. The detailed relationship between the morphologies (film morphology and internal nanomorphology) and the RS is revealed using impedance spectroscopy. The performance of the e-spray-PSCs is comparable to those of the PSCs that are fabricated using the SC method under identical conditions. Therefore, the e-spray method can be used to fabricate ultralow-cost PSCs, because of the performance results combined with the intrinsic advantages that the e-spray method is simple and has a low materials loss.

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