Performance Optimization of Polymer Solar Cells Using Electrostatically Sprayed Photoactive Layers

Abstract

Polymer solar cells (PSCs) are fabricated using a novel fi lm 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 fi eld. The performance of PSCs is primarily infl uenced by the inherent fi lm morphology of the e-sprayed polymer-blend active layers, which is signifi - cantly different from that of the conventional fi lms 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 infl uences device effi ciency. The internal series resistance ( R S ) of the PSCs that are formed using the e-spray method (e-spray-PSC) is signifi cantly reduced by a solvent vapor soaking (SVS) treatment in addition to the conventional thermodynamic nanomorphology controls. The detailed relationship between the morphologies (fi lm morphology and internal nanomorphology) and the R S 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.