Efficient bilayer heterojunction polymer solar cells with bumpy donor–acceptor interface formed by facile polymer blend

We demonstrated a facile method for the fabrication of bilayer polymer solar cells with a controlled heterojunction structure via simple polymer blends. The spontaneous phase separation of poly(3-hexylthiophene)/polyethylene glycol blends provides a bumpy electron-donor layer with characteristic circular depressions. The diameter and depth of the circular depressions can be controlled by varying the PEG content of the blend. The deposition of [6] and [6]-phenyl-C61-butyric acid methyl ester as an electron-acceptor layer then creates an interpenetrating donor–acceptor interface for bilayer heterojunction polymer solar cells. The bumpy morphology of the interface results in a significant enhancement in the power conversion efficiency over that of the bilayer polymer solar cells with a typical planar interface, which is mainly due to an increase of photocurrent. An estimation of the field-dependent possibility of charge separation indicates that charge extraction is more efficient than charge recombination in the bilayer devices and the increase in the interfacial area of solar cells with a bumpy-interface leads to generate more electron-hole pairs at the interface.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Bumpy structured photoactive layer fabricated by simple polymer blends. ► This method is one-step, mold free and simple solution process. ► Bumpy structured cell shows maximum power conversion efficiency of 3.87%.