CH3NH3PbBr3 Perovskite Solar Cells for Tandem Application – Demonstrations and Characterizations

摘要

Perovskite solar cells based on organometal halides have experienced an unprecedentedly rapid development since 2012, when the first efficient perovskite-based solar device with solid-state structure was reported. Increasing amount of research interests are focusing on characterizing material properties, developing deposition methods, resolving the instability and toxicity, as well as designing tandem structure. This thesis will present a comprehensive study of CH3NH3PbBr3 perovskite-based solar cell, including a novel deposition method for high efficiency CH3NH3PbBr3 solar cells, which shows substantial improvement over conventional one-step solution process, not only in the power conversion efficiency (1.7% vs 9.1%), but also in hysteresis. In the material characterization section, a study using one-photon and two-photon microscopy was conducted to reveal additional insight in the understanding of grain formation and carrier extraction. Then an investigation on fluorescence blinking in vapour-assisted deposited film was performed to study charge accumulation and migration. In the last part of this section, a dynamic aging study of vapour-assisted deposited film was carried out to demonstrate the spontaneously grain growing and defect generation. In this study, FLIM (Fluorescence lifetime imaging microscopy) was used to reveal the carrier lifetime of deposited film in a larger scale. The final aim of this thesis is to demonstrate the potential of using CH3NH3PbBr3 for tandem application. Therefore, a four-terminal tandem structure was demonstrated using spectrum-splitting approach. In this work, a great potential was shown when CH3NH3PbBr3 cell is coupled with a CH3NH3PbI3 cell; when a CH3NH3PbBr3 cell is coupled with a high efficiency PERL (passivated emitter rear locally diffused) silicon solar cell; and when a CH3NH3PbBr3 cell is coupled with a commercial screen printed silicon solar cell demonstrating power conversion efficiencies at 13.4%, 23.4% and 18.8% respectively. The last section of this thesis demonstrated a 2-terminal monolithic FTO/compact TiO2/mesoporous TiO2/CH3NH3PbI3/Spiro-OMeTAD/PEDOT: PSS/C60/CH3NH3PbBr3/Spiro-OMeTAD/Au solar cell by developing a novel composite carrier recombination stack which protects the underlying sub-cell and provides an interconnection with matching working functions. Remarkable voltage output at 1.96 V was obtained with the designed structure. In addition, simulation work shows the potential of this structure with further performance improvement to be expected.