16.5% Polymer Solar Cells with 6-Aminocaproic Acid-Modified ZnO as a Cathodic Interface Layer

Cathodic interface layers are important in determining the charge carrier collection and performance of polymer solar cells (PSCs). In this work, 6-aminocaproic acid (6-ACA) is successfully incorporated into sol-gel-derived zinc oxide (ZnO) to form 6-ACA-ZnO that can be used as a cathodic interface layer (CIL) in PM6:Y6 inverted polymer solar cells (i-PSCs). The work function of ZnO films can be reduced from 4.53 to 4.10 eV, thus effectively increasing the built-in electric field and enhancing the electron extraction efficiency. Furthermore, the partial substitution of undercoordinated oxygen vacancy by nitrogen atoms can effectively passivate the interface defects, thereby substantially increasing the electron mobility and conductivity to facilitate electron transport and reduce the carrier recombination loss. The i-PSCs based on 6-ACA-ZnO exhibit a power conversion efficiency (PCE) up to 16.50%, which is remarkably higher than the 15.30% of devices based on pristine ZnO. 6-ACA-ZnO can also be successfully applied to other nonfullerene and fullerene-based i-PSCs. The results indicate that 6-ACA-ZnO can be used as CILs to effectively improve the PCE of i-PSCs.

Automated summary

The research successfully incorporated 6-aminocaproic acid into sol-gel-derived zinc oxide to form 6-ACA-ZnO, which can be used as a cathodic interface layer in polymer solar cells, effectively improving their performance. The 6-ACA-ZnO demonstrated enhanced electron extraction efficiency and reduced carrier recombination loss, leading to a higher power conversion efficiency compared to devices using pristine ZnO.