title: Guanidinium: A Route to Enhanced Carrier Lifetime and Open-Circuit Voltage in Hybrid Perovskite Solar Cells.
abstract: Hybrid perovskites have shown astonishing power conversion efficiencies owed to their remarkable absorber characteristics including long carrier lifetimes, and a relatively substantial defect tolerance for solution-processed polycrystalline films. However, nonradiative charge carrier recombination at grain boundaries limits open circuit voltages and consequent performance improvements of perovskite solar cells. Here we address such recombination pathways and demonstrate a passivation effect through guanidinium-based additives to achieve extraordinarily enhanced carrier lifetimes and higher obtainable open circuit voltages. Time-resolved photoluminescence measurements yield carrier lifetimes in guanidinium-based films an order of magnitude greater than pure-methylammonium counterparts, giving rise to higher device open circuit voltages and power conversion efficiencies exceeding 17%. A reduction in defect activation energy of over 30% calculated via admittance spectroscopy and confocal fluorescence intensity mapping indicates successful passivation of recombination/trap centers at grain boundaries. We speculate that guanidinium ions serve to suppress formation of iodide vacancies and passivate under-coordinated iodine species at grain boundaries and within the bulk through their hydrogen bonding capability. These results present a simple method for suppressing nonradiative carrier loss in hybrid perovskites to further improve performances toward highly efficient solar cells.
authors.affiliation: Department of Materials Science and Engineering, ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States.
authors.forename: Nicholas
authors.initials: N
authors.lastname: De Marco
authors.affiliation: Department of Materials Science and Engineering, ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States.
authors.forename: Huanping
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Department of Materials Science and Engineering, ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States.
authors.forename: Qi
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Department of Materials Science and Engineering, ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States.
authors.forename: Pengyu
authors.initials: P
authors.lastname: Sun
authors.affiliation: Department of Materials Science and Engineering, ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States.
authors.forename: Zonghao
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Materials Science and Engineering, ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States.
authors.forename: Lei
authors.initials: L
authors.lastname: Meng
authors.affiliation: Department of Materials Science and Engineering, ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States.
authors.forename: En-Ping
authors.initials: EP
authors.lastname: Yao
authors.affiliation: Department of Materials Science and Engineering, ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States.
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Materials Science and Engineering, ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States.
authors.forename: Andy
authors.initials: A
authors.lastname: Schiffer
authors.affiliation: Department of Materials Science and Engineering, ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States.
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry*; D011211:Electric Power Supplies; D019791:Guanidine / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D012993:Solar Energy; D012996:Solutions / Q000737:chemistry; D013472:Sunlight; D014025:Titanium / Q000737:chemistry*
chemical_list: D017610:Calcium Compounds; D010087:Oxides; D012996:Solutions; C059910:perovskite; D014025:Titanium; D019791:Guanidine
keywords: Perovskite; carrier lifetime; guanidinium; open circuit voltage; passivation; solar cell