Molecular engineering of conjugated polymers for efficient hole transport and defect passivation in perovskite solar cells. (March 2018)

• Record Type: Journal Article
• Authors: Cai, Feilong; Cai, Jinlong; Yang, Liyan; Li, Wei; Gurney, Robert S.; Yi, Hunan; Iraqi, Ahmed; Liu, Dan; Wang, Tao
• Is Part Of: Nano energy. Volume 45(2018)
• Page Start: 28
• Page End: 36
• Publication Date: 2018-03
• Subjects: Perovskite solar cells -- Hole transport -- Defect passivation -- Conjugated polymer; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2017.12.028
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: Organic-inorganic hybrid perovskite solar cells represent an exceptional candidate for next-generation photovoltaic technology. However, the presence of surface defects in perovskite crystals limits the performance as well as the stability of perovskite solar cells. We have employed a series of carbazole and benzothiadiazole (BT) based donor-acceptor copolymers, which have different lengths of alkoxy side-chains grafted on the BT unit, as the dopant-free hole transport materials (HTMs) for perovskite solar cells. We demonstrate that although these side-chains can reduce the π−π stacking structural order of these copolymers to affect the hole transport properties, the methoxy unit introduces a desired defect passivation effect. Compared to the Spiro-OMeTAD-based device, the copolymer with methoxy side-chains on the BT unit (namely PCDTBT1) as the HTM achieved superior power conversion efficiency and stability due to efficient hole transport and the suppression of trap-induced degradation, whilst the copolymer with octyloxy side-chains on the BT unit (namely PCDTBT8) as the HTM lead to poor performance and stability. Graphical abstract: A series of carbazole and benzothiadiazole (BT) based copolymers have been employed as the dopant-free hole transport materials (HTMs) for perovskite solar cells. The side-chains of these HTM can reduce the π−π stacking structural order but can also introduce desired defect passivation effect.fx1 Highlights: Perovskite solar cells with PCEs over 19% were achieved using dopant-free HTMs. The thiophene and methoxy units introduce a desired defect passivation effect. PCDTBT1 passivates surface defects of perovskite and suppresses charge recombination.