title: Enhancement of the photovoltaic performance of CH₃NH₃PbI₃ perovskite solar cells through a dichlorobenzene-functionalized hole-transporting material.
abstract: A dichlorobenzene-functionalized hole-transporting material (HTM) is developed for a CH3NH3PbI3-based perovskite solar cell. Notwithstanding the similarity of the frontier molecular orbital energy levels, optical properties, and hole mobility between the functionalized HTM [a polymer composed of 2'-butyloctyl-4,6-dibromo-3-fluorothieno[3,4-b]thiophene-2-carboxylate (TT-BO), 3',4'-dichlorobenzyl-4,6-dibromo-3-fluorothieno[3,4-b]thiophene-2-carboxylate (TT-DCB), and 2,6-bis(trimethyltin)-4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene (BDT-EH), denoted PTB-DCB21] and the nonfunctionalized polymer [a polymer composed of thieno[3,4-b]thiophene (TT) and benzo[1,2-b:4,5-b']dithiophene (BDT), denoted PTB-BO], a higher power conversion efficiency for PTB-DCB21 (8.7%) than that for PTB-BO (7.4%) is achieved because of a higher photocurrent and voltage. The high efficiency is even obtained without including additives, such as lithium bis(trifluoromethanesulfonyl)imide and/or 4-tert-butylpyridine, that are commonly used to improve the conductivity of the HTM. Transient photocurrent-voltage studies show that the PTB-DCB21-based device exhibits faster electron transport and slower charge recombination; this might be related to better interfacial contact through intermolecular chemical interactions between the perovskite and the 3,4-dichlorobenzyl group in PTB-DCB21.
authors.affiliation: School of Chemical Engineering and Department of Energy Science, Sungkyunkwan University, Suwon, 440-746 (Korea), Fax: (+82) 31-290-7241.
authors.forename: Jin-Wook
authors.initials: JW
authors.lastname: Lee
authors.forename: Sungmin
authors.initials: S
authors.lastname: Park
authors.forename: Min Jae
authors.initials: MJ
authors.lastname: Ko
authors.forename: Hae Jung
authors.initials: HJ
authors.lastname: Son
authors.forename: Nam-Gyu
authors.initials: NG
authors.lastname: Park
keywords: electrochemistry; perovskite phases; polymers; semiconductors; solar cells