In this work, the morphology of BiFeO3 was successfully modulated from microsphere to microcube by using a polyanion, poly (methyl vinyl ether-alt-maleic acid) (PMVEMA), in a microwave assisted hydrothermal route. A simple ultrasonic purification method has been developed to obtain pure phase BiFeO3 from the crude products without using any chemicals. X-ray diffraction results confirmed the capability of this purification method. When increasing the amount of PMVEMA, the morphology of BiFeO3 gradually changed from microsphere to microcube as illustrated by scanning electron microscopy. A mechanism was suggested for the morphology evolution of BiFeO3. After the formation of the small BiFeO3 single crystal, PMVEMA preferentially absorbed on one side of the crystals through specific and/or noncovalent interactions, resulting in the preferential integration of these crystals to form microcubes. The magnetic properties of these microcrystals were also investigated and the magnetization of the microcubes increased with the decrease of temperature.
Jian Sun,Liang Chen,Zhipeng Liu,Zhiwei Gu,Lixin Song,Pingfan Du
Nonradiative recombination losses induced by surface and grain boundary defects in perovskite films severely limit their power conversion efficiency (PCE) and stability. In this study, effective passivation of film defects was achieved by incorporating poly(methyl vinyl ether-alt-maleic anhydride) (PMVEMA) into the perovskite precursor solution. The carbonyl groups (C═O) in PMVEMA coordinate with Pb2+ ions, thereby enhancing crystallinity, suppressing carrier recombination, and reducing trap-state density. Additionally, the hydrophobic groups in PMVEMA contribute to enhanced environmental stability of the perovskite films, and its flexible polymer chains significantly improve the mechanical flexibility of the devices. Experimental results demonstrate that PMVEMA-modified rigid and flexible devices achieved PCEs of 22.12 and 20.05%, respectively, under ambient air conditions. Moreover, after 600 h of storage in the dark, the devices retained 85% of their initial efficiency, compared to only 44% for the control devices. This study highlights the potential of PMVEMA as a functional additive for enhancing the performance and stability of perovskite solar cells (PSCs), providing an effective strategy for the development of efficient and flexible photovoltaic devices.
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