Influence of alkanediol series as processing additives in photo-active layer on the power conversion efficiency of polymer solar cells

The alkanediol series such as 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol and 1,10-decanediol was introduced to poly(3-hexylthiophene, P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) based bulk-heterojunction (BHJ) polymer solar cells as processing additives. When 1,3-propanediol was introduced to photo-active layer as a processing additive, power conversion efficiency (PCE) was dramatically increased from 3.5% (for the reference device) to 5.3%. To investigate the causes of improvement of the PCE of PSCs after addition of alkanediol series, photon absorbance properties were observed using UV–vis spectroscopy and photoluminescence (PL). Then, the degree of crystallinity of P3HT was examined through X-ray analysis. In addition, changes in the nano-structure and surface morphology of P3HT:PCBM blend film were observed through AFM and TEM. The series resistance (RS) of the fabricated PSCs was 5.19 Ω cm2, and short circuit current density (JSC), open circuit voltage (VOC) and fill factor (FF) were 16.2 mA/cm2, 0.63 V and 51.9% respectively.