title: Additive-assisted control over phase-separated nanostructures by manipulating alkylthienyl position at donor backbone for solution-processed, non-fullerene, all-small-molecule solar cells.
abstract: A non-fullerene, all-small-molecule solar cell (NF-SMSC) device uses the blend of a small molecule donor and a small molecule acceptor as the active layer. Aggregation ability is a key factor for this type of solar cell. Herein, we used the alkylthienyl unit to tune the aggregation ability of the diketopyrrolopyrrole (DPP)-based small molecule donors. Replacing two alkoxyl units in BDT-O-DPP with two alkylthienyl units yields BDT-T-DPP, and further introducing another two alkylthienyl units into the backbone produces BDT-T-2T-DPP. With the introduction of alkylthienyl, the backbone becomes twisted. As a result, the ππ-stacking strength, aggregation ability, and crystallite size all obey the sequence of BDT-O-DPP > BDT-T-DPP > BDT-T-2T-DPP. When selected a reported perylene diimide dimer of bis-PDI-T-EG as acceptor, the best NF-SMSC device exhibits a power conversion efficiency of 1.34, 2.01, and 1.62%, respectively, for the BDT-O-DPP, BDT-T-DPP, and BDT-T-2T-DPP based system. The BDT-T-DPP/bis-PDI-T-EG system yields the best efficiency of 2.01% among the three combinations. This is due to the moderate aggregation ability of BDT-T-DPP yields moderate phase size of 30-50 nm, whereas the strong aggregation ability of BDT-O-DPP gives a bigger size of 50-80 nm, and the weak aggregation ability of BDT-T-2T-DPP produces a smaller size of 10-30 nm. The BDT-T-DPP/bis-PDI-T-EG combination exhibits balanced hole/electron mobility of 0.022/0.016 cm(2)/(V s), whereas the BDT-O-DPP/bis-PDI-T-EG and the BDT-T-2T-DPP/bis-PDI-T-EG blend show a hole/electron mobility of 0.0011/0.0057 cm(2)/(V s) and 0.0016/0.11 cm(2)/(V s), respectively.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, P. R. China .
authors.forename: Jianhua
authors.initials: J
authors.lastname: Huang
authors.forename: Xue
authors.initials: X
authors.lastname: Wang
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Zhixiao
authors.initials: Z
authors.lastname: Niu
authors.forename: Zhenhuan
authors.initials: Z
authors.lastname: Lu
authors.forename: Bo
authors.initials: B
authors.lastname: Jiang
authors.forename: Yuxi
authors.initials: Y
authors.lastname: Sun
authors.forename: Chuanlang
authors.initials: C
authors.lastname: Zhan
authors.forename: Jiannian
authors.initials: J
authors.lastname: Yao