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Development of Efficient Charge-Selective Materials for Bulk Heterojunction Polymer Solar Cells
Final rept. 31 Aug 2011-30 Aug 2014
WASHINGTON UNIV SEATTLE
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The focus of this research project was to develop novel charge selective materials to improve the performance of polymer solar cells. Interfacial engineering has been identified as an important section in bulk heterojunction polymer solar cells to maximize power conversion efficiency since it can effectively alleviate energy barriers at interfaces in multi-layered architectures, particularly for the organicelectrode interfaces, and thus to facilitate charge transportextraction in the device. In this regard, a series of self-doped fullerene materials with much increased conductivity compared to the parent semiconducting fullerenes was developed. The self-doping mechanism was clarified to result from the anion-induced electron transfer AIET from constituent iodide to adjacent fullerene core during film evolution. Benefitting from their proper energy levels and decent conductivity, these fullerene derivatives can serve as efficient electron extraction layers EELs in both conventional and inverted PSCs. On one hand, they serve as the cathode-independent interlayers in the conventional PSCs owing to their electrode WF tuning capability. On the other hand, their high conductivities enable them to be less thickness sensitive 16-50 nm in the inverted structure to result in a promising PCEs of up to 9.62 in the inverted PTB7-ThPC71BM device. Moreover, extending from this n-doping strategy, further development resulted in a crosslinkable self-doped fullerene composite interlayer, which possesses respectable solvent resistance, decent conductivity, and electrode WF tuning capability. In addition, these fullerene-based EELs have also been applied into perovskite solar cells PVSCs to obtain improved device performance and stability. All these results affirm the great potential of using FPI-based EELs for achieving high-efficiency PSCs and PVSCs.
APPROVED FOR PUBLIC RELEASE