Modified metal oxides with polymer zwitterions to boost organic solar cells

Organic solar cells have attracted much attention due to their light weight, flexibility and suitability for wearable applications. However, long-term device stability remains an obstacle to the full implementation of organic solar cells.

Zinc oxide (ZnO) has emerged as a promising electron transport layer for optoelectronic devices due to its excellent charge carrier mobility. Nonetheless, the performance of ZnO-based devices is often limited by film defects that act as charge trapping sites.

In a study published in the KeAi journal Wearable Electronics, a group of researchers from China and The Unites States, outline a new strategy they have developed —  polymer zwitterions incorporating conjugated units to modify zinc oxide (ZnO) interlayers in organic solar cells, which effectively passivates defects and enhances solar cell device performance and stability.

“ZnO films often contain numerous defects which act as electron traps and recombination centers, degrading device performance. To address this, metals, organic molecules and polymers have been introduced into ZnO films for defect passivation and modification,” explains the study's senior author Yao Liu, a professor in Advanced Innovation Center for Soft Matter Science and Engineering at Beijing University of Chemical Technology. “The passivation effect of the modifier and the resultant enhancement in device stability represent critical considerations in the development of high-performance optoelectronics,”

The researchers found that the synthesized polymer zwitterions with conjugated units effectively passivated defects in the ZnO film, improving its electrical properties while simultaneously adjusting energy level to facilitate more efficient charge extraction.

“The conjugated units enhance UV light absorption, thereby mitigating UV-induced degradation of photoactive layer materials in solar cell devices.,” shares Liu. “The polymer zwitterions modification strategy significantly enhanced device performance and long-term stability.”

The team’s findings expand the repertoire of polymeric modifiers for ZnO interlayer and establishes polymer zwitterion modification as a promising strategy for developing high-performance metal oxide charge transport layers in organic photovoltaics.

“Polymer zwitterion-modified ZnO is a promising material candidate for flexible and wearable electronics, uniquely combining mechanical durability with stable electrical performance,” adds Liu.

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Contact the author: Aijun Gao, State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, China, gaoaj@mail.buct.edu.cn

Yao Liu, State Key Laboratory of Chemical Resource Engineering, Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, China, liuyao@mail.buct.edu.cn

The publisher KeAi was established by Elsevier and China Science Publishing & Media Ltd to unfold quality research globally. In 2013, our focus shifted to open access publishing. We now proudly publish more than 200 world-class, open access, English language journals, spanning all scientific disciplines. Many of these are titles we publish in partnership with prestigious societies and academic institutions, such as the National Natural Science Foundation of China (NSFC).