| Summary: | 碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 107 === Perovskite solar cells (PSCs) have drawn enormous attention in recent years owing to their high power conversion efficiency over 20%. Some of its exceptional properties such as remarkably high absorption over the visible spectrum, long charge carrier diffusion lengths in the μm range, and tunable band gap by interchanging various structure ions reveal its great potential in solar conversion. Nevertheless, in order to promote carrier transmission efficiency of devices, how to elevate the ability to quench carriers aiding with other material layers’ aiding is an important issue nowadays.
In the beginning, perovskite added Louis base is proofed to facilitate power conversion efficiency of perovskite solar cells; therefore, urea is adopted and successfully promotes efficiencies of devices. However, it is confirmed by papers that zinc oxide (ZnO) and tin oxide (SnO2) possess higher electron mobility and more suitable band structure, which are considered to be the replacements of TiO2 ETL. After analyzing surface morphology, X-ray diffraction, and carrier quenching efficiency, it is understood that ZnO coated perovskite is quite unstable and quickly degrades in atmosphere. Besides, tin oxide demonstrates the best transmission rate in three of them, so this metal oxide electron transport material is chose to do the next step of surface modification.
The second is introducing the surface modification material to effectively separate excitons into carriers and for them to be quenched by ETL. Here, C60 pyrrolidine tris-acid (CPTA) and [6,6]-phenyl- C61-butyric acid methyl ester (PCBM) are separately passivated on SnO2 for comparison. In the past, PCBM was usually adopted in inverted perovskite solar cell as an organic electron transport layer, and it has been found that it could be used in surface as well modification in recent years. However, surface morphology, X-ray diffraction and photoluminescence (PL) show that CPTA transfers carrier more efficiently. In FTIR data analysis, the further study comprehends that the hydroxyl terminal groups on CPTA are coordinated with oxygen-vacancy-related defects of Sn in SnO2, and chemical bonding with interface modification brings better transfer ability than PCBM with non-bonding passivation on SnO2, forasmuch it is more advisable to be applied in facilitating performance of perovskite solar cells.
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