Dual nanocomposite carrier transport layers enhance the efficiency of planar perovskite photovoltaics

In photovoltaic devices, more effective transfer of dissociated electrons and holes from the active layer to the respective electrodes will result in higher fill factors and short-circuit current densities and, thus, enhanced power conversion efficiencies (PCEs). Planar perovskite photovoltaics feat...

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Bibliographic Details
Published in:RSC advances 2018-01, Vol.8 (23), p.12526-12534
Main Authors: Lin, Hsi-Kuei, Li, Jia-Xing, Wang, Hao-Cheng, Su, Yu-Wei, Wu, Kaung-Hsiung, Wei, Kung-Hwa
Format: Article
Language:English
Subjects:
Atomic force microscopy
Atomic structure
Butyric acid
Carrier recombination
Carrier transport
Charge transport
Chemistry
Diffusion layers
Diffusion length
Electron microscopy
Electron mobility
Electron transport
Energy conversion efficiency
Energy levels
Hole mobility
Micrometers
Microscopy
Molybdenum disulfide
Nanocomposites
Photovoltaic cells
Short circuits
Small angle X ray scattering
Solar cells
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Summary:In photovoltaic devices, more effective transfer of dissociated electrons and holes from the active layer to the respective electrodes will result in higher fill factors and short-circuit current densities and, thus, enhanced power conversion efficiencies (PCEs). Planar perovskite photovoltaics feature an active layer that can provide a large exciton diffusion length, reaching several micrometers, but require efficient carrier transport layers for charge extraction. In this study, we employed two nanocomposite carrier transfer layers-an electron transport layer (ETL) comprising [6,6]phenyl-C -butyric acid methyl ester (PC BM) doped with the small molecule 4,7-diphenyl-1,10-phenanthroline (Bphen), to enhance the electron mobility, and a hole transfer layer (HTL) comprising poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) doped with molybdenum disulfide (MoS ) nanosheets, to enhance the hole mobility. We used ultraviolet photoelectron spectroscopy to determine the energy levels of these composite ETLs and HTLs; atomic force microscopy and scanning electron microscopy to probe their surface structures; and transmission electron microscopy and synchrotron grazing-incidence small-angle X-ray scattering to decipher the structures of the ETLs. Adding a small amount (less than 1%) of Bphen allowed us to tune the energy levels of the ETL and decrease the size of the PC BM clusters and, therefore, generate more PC BM aggregation domains to provide more pathways for electron transport, leading to enhanced PCEs of the resulting perovskite devices. We used quantitative pump-probe data to resolve the carrier dynamics from the perovskite to the ETL and HTL, and observed a smaller possibility of carrier recombination and a shorter injection lifetime in the perovskite solar cell doubly modified with carrier transport layers, resulting in an enhancement of the PCE. The PCE reached 16% for a planar inverted perovskite device featuring an ETL incorporating 0.5 wt% Bphen within PC BM and 0.1 wt% MoS within PEDOT:PSS; this PCE is more than 50% higher than the value of 10.2% for the corresponding control device.
ISSN:2046-2069
2046-2069
DOI:10.1039/c8ra01532e