Hole Transfer in Dye-Sensitized Cesium Lead Halide Perovskite Photovoltaics: Effect of Interfacial Bonding

• Published in: The Journal of Physical Chemistry C
• Main Authors: Forde, Aaron, Kilin, Dmitri
• Language: unknown
• Published: 2021
• Subjects: 14 SOLAR ENERGY; 37 INORGANIC; ORGANIC; PHYSICAL; AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; Spiro; DML
• Online Access: http://www.osti.gov/servlets/purl/1480498; https://www.osti.gov/biblio/1480498; https://doi.org/10.1021/acs.jpcc.7b04961

Lead halide perovskites have gained attention as an active material in solid-state dye-sensitized photovoltaics due to their high absorption of visible light and long charge-transport lengths. In perovskite-based dye-sensitized photovoltaic architectures the perovskite material is typically paired with a hole-transport material, such as spiro-OMeTAD, which extracts a hole from the photoexcited perovskite to generate free charge carriers. In this study, we explored two competing charge-transfer pathways at the interface between lead halide perovskite and spiro-OMeTAD: “through-bond” and “through-space”. For the through-bond pathway we use a segment of spiro-OMeTAD that contains methoxy linker groups, which will be referred to as “dye with methoxy linker groups” (DML). For the through-space pathway we use a segment of spiro-OMeTAD with removed linker groups, triphenylamine, which will be referred to as “dye”. Four atomistic models were studied: (I) a periodic cesium lead iodide (CsPbI3) perovskite nanowire (NW) that is paired with the dye molecule, (II) a periodic CsPbI3 perovskite NW paired with the DML molecule where the linker groups form coordination bond to the surface of the nanowire, (III) a CsPbI 3 perovskite thin film (TF) paired with the dye molecule, and (IV) a CsPbI 3 perovskite TF paired with the DML molecule. Charge-transfer dynamics, providing rates of electron/hole relaxation and relaxation pathways, are calculated using reduced density matrix formalism using Redfield theory. Finally, it was found that the terminal surface of the perovskite (Pb–I vs Cs–I) has important implications for energetic alignment at the perovskite–dye interface due to band bending. Finally, computed charge-transfer rates match well with upper and lower bounds of reported experimental results where “fast” picosecond rates correspond to through-bond pathway and “slow” nanosecond rates correspond to through-space.