Improved Performance of Printable Perovskite Solar Cells with Bifunctional Conjugated Organic Molecule
Yue Hu a, Yaoguang Rong a, Hongwei Han a
a Huazhong University of Science and Technology, Michael Grazel Center for Mesoscopic Solar Cells, Wuhan National Laboratory for Optoelectronics, Wuhan, 430072, China
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV18)
Benidorm, Spain, 2018 May 28th - 31st
Organizers: Emilio Palomares and Rene Janssen
Poster, Yue Hu, 006
Publication date: 21st February 2018

The past few years have witnessed a rapid evolution of hybrid organic-inorganic perovskite solar cells (PSCs) with both low cost and boosted high power conversion efficiency (PCE) over 22%. Despite the achievements, MAPbI3 suffers from inherent instability over ambient operation conditions due to the low formation energy of the material itself and the high hydrophilicity of the organic cations. Efforts such as developing novel device architectures as well as exploring novel materials have been tried to improve the device stabilities. Among them, the two-dimensional (2D) perovskites that are crafted using bulkier alkylammonium cations in place of methylammonium exhibit appealing environmental stability. However, the insulating alkylammonium spacer cations hinder charge transport and limit the efficiencies of the devices based on such perovskites. In this scenario, an exploration of alternative yet effective organic spacer cations that increase the charge transfer is imperative to enhance the efficiency.

Herein, we design such an alternative bi-functional conjugated cation AB. We report the first time the incorporation of AB in 2D/3D perovskites and its implementation on solar cells. The use of bi-functional conjugated cations enhances significantly the performance of the cells, reaching a highest power conversion efficiency of 15.6% with improved stability. The efficiency remained around 90% of the initial value after 100 h continuous illumination, much more stable than MAPbI3 perovskite. By comparing this cation with a mono-functional cation and a bi-functional non-conjugated cation with similar structure, we found that the bi-functional conjugated cation not only benefits the growth of perovskite crystals in the mesoporous network, but also facilitates the charge transport. Our approach helps explore new rational designs of cations in perovskites.

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