title: A DMF-assisted solution process boosts the efficiency in P3HT:PCBM solar cells up to 5.31%.
abstract: To achieve ideal phase separation in P3HT:PCBM (1:1, w/w) blend films, a selective second solvent, DMF, which cannot dissolve P3HT but slightly dissolves PCBM, was added into 1,2-dichlorobenzene. Addition of 10% DMF led to better charge transport, better morphology and average power conversion efficiency (PCE) enhancement from 3.75% to 4.29%. To form an acceptor rich layer near the cathode and achieve effective vertical phase separation, PCBM solution in DMF was spin-coated on the top surface of the P3HT:PCBM active layer. The PCBM rich layer enhanced hole blocking and electron transport, leading to an average PCE improvement from 4.29% to 4.83% (for the PCBM rich layer formed by a 2 mg ml(-1) PCBM solution). Finally, to obtain more uniform and smooth films with better contact of Ca/PCBM and BHJ/PCBM interfaces, the films were thermally annealed at 120 ° C for 10 min after spin coating the PCBM rich layer, leading to an average PCE enhancement from 4.83% to 5.17% (the best PCE was 5.31%).
authors.affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China. University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
authors.forename: Pei
authors.initials: P
authors.lastname: Cheng
authors.forename: Yongfang
authors.initials: Y
authors.lastname: Li
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Zhan