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Well-Organized Mesoporous TiO2 Photoanode by Using Amphiphilic Graft Copolymer for Efficient Perovskite Solar Cells
journal contribution
posted on 2016-04-15, 00:00 authored by Chih-Chun Chung, Chang Soo Lee, Efat Jokar, Jong Hak Kim, Eric Wei-Guang DiauThe
control of the thickness and porosity of a mesoporous TiO2 layer is important to improve the photovoltaic performance of perovskite
solar cells. We produced organized mesoporous TiO2 (om-TiO2) layers using a low-cost amphiphilic graft copolymer, poly(vinyl
chloride)-graft-poly(oxyethylene methacrylate) (PVC-g-POEM), as a sacrificial template. This simple but effective
synthetic approach generates highly mesoporous and well-organized
TiO2 nanostructures with interconnected and size-tunable
features. Specifically, the average pore size increased with the amount
of hydrophobic PVC main chain in the graft copolymer, which acted
as the pore forming agent. Perovskite layers were prepared on top
of an om-TiO2 layer according to a two-step sequential
deposition: after coating the PbI2 solution in dimethylformamide
(DMF) on an om-TiO2 substrate, the substrate was prewetted
in isopropyl alcohol (IPA) solvent before immersing into a CH3NH3I/IPA solution. This prewetting treatment not
only improves the yields of conversion from PbI2 to CH3NH3PbI3, but also increases the size
of perovskite crystals with cuboid morphology. On varying the pore
size and the film thickness of the om-TiO2 layer, the device
performance attained 11.9% of power conversion efficiency (PCE) at
pore size 70 nm and film thickness 300 nm. We measured extracted charge
densities and decays of transient photovoltage to understand the kinetics
of charge recombination in relation to the corresponding device performance.
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chargeIPAsubstratefilm thickness 300 nmdevice performanceDMFmesoporous TiO 2 layerPCETiO 2 nanostructuresPbI 2 solutionamphiphilic graft copolymerEfficient Perovskite Solar CellsCH 3 NH 3pore sizepower conversion efficiencyPOEMAmphiphilic Graft Copolymerpore size 70 nmperovskitemesoporous TiO 2CH 3 NH 3 PbI 3
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