title: Graphene quantum dot incorporated perovskite films: passivating grain boundaries and facilitating electron extraction.
abstract: Organic-inorganic halide perovskites have emerged as attractive materials for use in photovoltaic cells. Owing to the existence of dangling bonds at the grain boundaries between perovskite crystals, minimizing the charge recombination at the surface or grain boundaries by passivating these trap states has been identified to be one of the most important strategies for further optimization of device performance. Previous reports have mainly focused on surface passivation by inserting special materials such as graphene or fullerene between the electron transfer layer and the perovskite film. Here, we report an enhanced efficiency of mesoscopic perovskite solar cells by using graphene quantum dots (GQDs) to passivate the grain boundaries of CH3NH3PbI3. The highest efficiency (17.62%) is achieved via decoration with 7% GQDs, which is an 8.2% enhancement with respect to a pure perovskite based device. Various analyses including electrochemical impedance spectroscopy, time-resolved photoluminescence decay and open-circuit voltage decay measurements are employed in investigating the mechanism behind the improvement in device performance. The findings reveal two important roles played by GQDs in promoting the performance of perovskite solar cells - that GQDs are conducive to facilitating electron extraction and can effectively passivate the electron traps at the perovskite grain boundaries.
authors.affiliation: School of Materials Science and Engineering, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Province Cultivation Base for State Key Laboratory of Photovoltaic Science and Technology, Changzhou University, Changzhou, 213164, Jiangsu, China. dingjn@cczu.eduy.cn nyyuan@cczu.edu.cn.
authors.forename: Xiang
authors.initials: X
authors.lastname: Fang
authors.affiliation: School of Materials Science and Engineering, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Province Cultivation Base for State Key Laboratory of Photovoltaic Science and Technology, Changzhou University, Changzhou, 213164, Jiangsu, China. dingjn@cczu.eduy.cn nyyuan@cczu.edu.cn and Micro/Nano Science and Technology Center, Jiangsu University, Zhenjiang, 212013, China.
authors.forename: Jianning
authors.initials: J
authors.lastname: Ding
authors.affiliation: School of Materials Science and Engineering, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Province Cultivation Base for State Key Laboratory of Photovoltaic Science and Technology, Changzhou University, Changzhou, 213164, Jiangsu, China. dingjn@cczu.eduy.cn nyyuan@cczu.edu.cn.
authors.forename: Ningyi
authors.identifier: http://orcid.org/0000-0002-9398-1105
authors.initials: N
authors.lastname: Yuan
authors.affiliation: School of Materials Science and Engineering, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Province Cultivation Base for State Key Laboratory of Photovoltaic Science and Technology, Changzhou University, Changzhou, 213164, Jiangsu, China. dingjn@cczu.eduy.cn nyyuan@cczu.edu.cn.
authors.forename: Peng
authors.initials: P
authors.lastname: Sun
authors.affiliation: School of Materials Science and Engineering, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Province Cultivation Base for State Key Laboratory of Photovoltaic Science and Technology, Changzhou University, Changzhou, 213164, Jiangsu, China. dingjn@cczu.eduy.cn nyyuan@cczu.edu.cn.
authors.forename: Minghang
authors.initials: M
authors.lastname: Lv
authors.affiliation: State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200500, China.
authors.forename: Guqiao
authors.initials: G
authors.lastname: Ding
authors.affiliation: School of Materials Science and Engineering, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Province Cultivation Base for State Key Laboratory of Photovoltaic Science and Technology, Changzhou University, Changzhou, 213164, Jiangsu, China. dingjn@cczu.eduy.cn nyyuan@cczu.edu.cn and State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200500, China.
authors.forename: Chong
authors.initials: C
authors.lastname: Zhu