Comprehensive interfacial charge transfer study of metal halide perovskite

Liu, M 2017, Comprehensive interfacial charge transfer study of metal halide perovskite, Doctor of Philosophy (PhD), Engineering, RMIT University.

Document type: Thesis
Collection: Theses

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Title Comprehensive interfacial charge transfer study of metal halide perovskite
Author(s) Liu, M
Year 2017
Abstract This thesis presents a study of the charge generation, separation, and recombination processes in organic-inorganic halide perovskite solar cells (OHPSCs) performed with time-resolved experimental techniques. Perovskite solar cells based on CH3NH3PbI3 (MAPbI3) as light absorber can be solution-processed on large areas by indicating high power conversion efficiency (>22%) and thus promise to become highly cost effective source of renewable energy. Although rapid and significant improvements of the power conversion efficiency over the last four years, the fundamental working principles of OHPSCs are still not fully understood. It is the aim of this thesis to clarify the role of different performance limiting processes in perovskite solar cells and to correlate them with characters of interfacial charge transfer dynamics at the perovskite interfaces, i.e. electron transfer material (ETM) / perovskite / hole transfer material (HTM).

By combining transient absorption spectroscopy and transient emission spectroscopy in various time scale (nanosecond to millisecond) and probe light range (visible to near infrared) a comprehensive analysis of the working principles of interfacial charge transfer kinetics in MAPbI3-based perovskite films could be performed. It was found that the excitation intensity severely influences the perovskite excited state lifetime and charge separation efficiency (electron and hole). The increase of excitation intensity accelerates the excited state lifetime while lowering the charge separation efficiency for both electron and hole injection yields. Moreover, the mesoscopic structure for OHPSCs has been proved to be more favorable to realize efficient electron injection compared to the planar heterojunction structure. Addition to the preferred mesoscopic structure, the best configuration for the design of perovskite device has been recommended that the perovskite absorber should be as thick as possible (>300 nm) while the mesoporous TiO2 layer is supposed to be as thin as possible (<150 nm). Excitation photon energy has been found to be another key factor to influence the charge transfer dynamics. Strong excitation energy (low wavelength) can accelerate the electron injection rate while also obtaining relatively short charge recombination lifetime. The overall high performance of perovskite solar cells is highly correlated with efficient hole injection yield that is almost independent on either perovskite layer thickness or excitation energy, and also prolonged charge recombination kinetics. It is crucial to carefully consider the future application environment for perovskite solar cells based on current film structure (mp-TiO2 / MAPbI3 / OMeTAD), for instance, they are not suitable for high power concentrator photovoltaics (>100 sun).
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Engineering
Subjects Structural Chemistry and Spectroscopy
Optical Properties of Materials
Keyword(s) perovskite solar cells
charge transfer dynamics
electron and hole transfer materials
transient absorption spectrometer
interfacial molecular engineering
time-resolved photoluminiscence
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Created: Wed, 08 Nov 2017, 10:36:53 EST by Denise Paciocco
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