Elusive Presence of Chloride in Mixed Halide Perovskite Solar Cells.
The role of chloride in the MAPbI3-xClx perovskite is still limitedly understood, albeit subjected of much debate. Here, we present a combined angle-resolved X-ray photoelectron spectroscopy (AR-XPS) and first-principles DFT modeling to investigate the MAPbI3-xClx/TiO2 interface. AR-XPS analyses carried out on ad hoc designed bilayers of MAPbI3-xClx perovskite deposited onto a flat TiO2 substrate reveal that the chloride is preferentially located in close proximity to the perovskite/TiO2 interface. DFT calculations indicate the preferential location of chloride at the TiO2 interface compared to the bulk perovskite due to an increased chloride-TiO2 surface affinity. Furthermore, our calculations clearly demonstrate an interfacial chloride-induced band bending, creating a directional "electron funnel" that may improve the charge collection efficiency of the device and possibly affecting also recombination pathways. Our findings represent a step forward to the rationalization of the peculiar properties of mixed halide perovskite, allowing one to further address material and device design issues.
†NNL - National Nanotechnology Laboratory, CNR Istituto Nanoscienze, Distretto Tecnologico, Via Arnesano 16, 73100 Lecce, Italy.
Silvia
S
Colella
‡Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), CNR-ISTM, Via Elce di Sotto 8, Perugia I-06123, Italy.
Edoardo
E
Mosconi
§CNR-IMM, Istituto per la Microelettronica e Microsistemi, Strada VIII n°5, 95121 Catania, Italy.
Giovanna
G
Pellegrino
§CNR-IMM, Istituto per la Microelettronica e Microsistemi, Strada VIII n°5, 95121 Catania, Italy.
Alessandra
A
Alberti
†NNL - National Nanotechnology Laboratory, CNR Istituto Nanoscienze, Distretto Tecnologico, Via Arnesano 16, 73100 Lecce, Italy.|∇Dipartimento di Matematica e Fisica "E. De Giorgi", Universita' del Salento, Via per Arnesano, 73100 Lecce, Italy.
Valentino L P
VL
Guerra
†NNL - National Nanotechnology Laboratory, CNR Istituto Nanoscienze, Distretto Tecnologico, Via Arnesano 16, 73100 Lecce, Italy.|⊥Center for Bio-Molecular Nanotechnology, Fondazione Istituto Italiano di Tecnologia, Via Barsanti, 73010 Arnesano (Lecce), Italy.|∇Dipartimento di Matematica e Fisica "E. De Giorgi", Universita' del Salento, Via per Arnesano, 73100 Lecce, Italy.
Sofia
S
Masi
†NNL - National Nanotechnology Laboratory, CNR Istituto Nanoscienze, Distretto Tecnologico, Via Arnesano 16, 73100 Lecce, Italy.|⊥Center for Bio-Molecular Nanotechnology, Fondazione Istituto Italiano di Tecnologia, Via Barsanti, 73010 Arnesano (Lecce), Italy.
Andrea
A
Listorti
†NNL - National Nanotechnology Laboratory, CNR Istituto Nanoscienze, Distretto Tecnologico, Via Arnesano 16, 73100 Lecce, Italy.
Aurora
A
Rizzo
#Università degli studi di Catania and INSTM UdR Catania, Viale Andrea Doria 6, 95125 Catania, Italy.
Guglielmo Guido
GG
Condorelli
‡Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), CNR-ISTM, Via Elce di Sotto 8, Perugia I-06123, Italy.
Filippo
F
De Angelis
†NNL - National Nanotechnology Laboratory, CNR Istituto Nanoscienze, Distretto Tecnologico, Via Arnesano 16, 73100 Lecce, Italy.|⊥Center for Bio-Molecular Nanotechnology, Fondazione Istituto Italiano di Tecnologia, Via Barsanti, 73010 Arnesano (Lecce), Italy.|∇Dipartimento di Matematica e Fisica "E. De Giorgi", Universita' del Salento, Via per Arnesano, 73100 Lecce, Italy.
Giuseppe
G
Gigli
DFT investigations; X-ray photoelectron spectroscopy; chloride; perovskites; photovoltaics