title: Interface engineering to enhance the efficiency of conventional polymer solar cells by alcohol-/water-soluble C60 materials doped with alkali carbonates.
abstract: Two new C60-based n-type materials, EGMC-OH and EGMC-COOH, functionalized with hydrophilic triethylene glycol groups (TEGs), have been synthesized and employed in conventional polymer solar cells. With the assistance of the TEG-based surfactant, EGMC-OH and EGMC-COOH can be dissolved in highly polar solvents to implement the polar/nonpolar orthogonal solvent strategy, forming an electron modification layer (EML) without eroding the underlying active layer. Multilayer conventional solar cells on the basis of ITO/PEDOT:PSS/P3HT:PC61BM/EML/Ca/Al configuration with the insertion of the EGMC-OH and EGMC-COOH EML between the active layer and the electrode have thus been successfully realized by cost-effective solution processing techniques. Moreover, the electron conductivity of the EML can be improved by incorporating alkali carbonates into the EGMC-COOH EML. Compared to the pristine device with a PCE of 3.61%, the devices modified by the Li2CO3-doped EGMC-COOH EML achieved a highest PCE of 4.29%. Furthermore, we demonstrated that the formation of the EGMC-COOH EML can be utilized as a general approach in the fabrication of highly efficient multilayer conventional devices. With the incorporation of the EGMC-COOH doped with 40 wt % Li2CO3, the PCDCTBT-C8:PC71BM-based device exhibited a superior PCE of 4.51%, which outperformed the corresponding nonmodified device with a PCE of 3.63%.
authors.affiliation: Department of Applied Chemistry, National Chiao Tung University, Hsin-Chu, Taiwan.
authors.forename: Yu-Ying
authors.initials: YY
authors.lastname: Lai
authors.forename: Ping-I
authors.initials: PI
authors.lastname: Shih
authors.forename: Yi-Peng
authors.initials: YP
authors.lastname: Li
authors.forename: Che-En
authors.initials: CE
authors.lastname: Tsai
authors.forename: Jhong-Sian
authors.initials: JS
authors.lastname: Wu
authors.forename: Yen-Ju
authors.initials: YJ
authors.lastname: Cheng
authors.forename: Chain-Shu
authors.initials: CS
authors.lastname: Hsu