title: Decoupling Interfacial Charge Transfer from Bulk Diffusion Unravels Its Intrinsic Role for Efficient Charge Extraction in Perovskite Solar Cells.
abstract: In a perovskite solar cell, the overall photoinduced charge-transfer (CT) process comprises both charge diffusion through the bulk to perovskite/electrode interfaces and interfacial electron and hole transfer to electrodes. In this study, we decoupled these two entangled processes by investigating the film thickness-dependent CT dynamics from CH3NH3PbI3perovskites to [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) (electron acceptor) and spiro-OMeTAD (hole acceptor). By fitting ultrafast transient absorption kinetics to an explicit "diffusion-coupled charge-transfer" model, we found that the charge diffusion from the film interior to perovskite/electrode interfaces took ∼200 ps to a few nanoseconds, depending on the thickness of perovskite film; the subsequent interfacial charge transfer was ultrafast, ∼6 ps for electron transfer to PCBM and ∼8 ps for hole transfer to spiro-OMeTAD, and led to efficient charge extraction (>90%) to electrodes in a 400 nm thick film. Our results indicate that the picosecond interfacial charge transfer is a key to high-performance perovskite solar cells.
authors.affiliation: State Key Laboratory of Molecular Reaction Dynamics and Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Dalian Institute of Chemical Physics, Chinese Academy of Sciences , Dalian 116023, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Leng
authors.affiliation: State Key Laboratory of Molecular Reaction Dynamics and Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Dalian Institute of Chemical Physics, Chinese Academy of Sciences , Dalian 116023, China.|State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum , 66 Changjiang West Road, Huangdao District, Qingdao 266580, China.
authors.forename: Junxue
authors.identifier: http://orcid.org/0000-0001-8349-1017
authors.initials: J
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum , 66 Changjiang West Road, Huangdao District, Qingdao 266580, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Molecular Reaction Dynamics and Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Dalian Institute of Chemical Physics, Chinese Academy of Sciences , Dalian 116023, China.
authors.forename: Shengye
authors.identifier: http://orcid.org/0000-0003-2001-2212
authors.initials: S
authors.lastname: Jin