Regular Article

Improving the stabilities of organic solar cells via employing a mixed cathode buffer layer

¹ Hebei Key Laboratory of Functional Polymers, School of Chemical Engineering, Hebei University of Technology, Tianjin 300130, P.R. China
² State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130023, Jilin Province, P.R. China

^* e-mail: qindashan@hebut.edu.cn

Received: 7 July 2021
Received in final form: 26 August 2021
Accepted: 27 August 2021
Published online: 14 September 2021

Abstract

Organic solar cells (OSCs) have been fabricated using cathode buffer layers based on bathocuproine (BCP) and 4,4'-N,N'-dicarbazole-biphenyl (CBP). It is found that despite nearly same power conversion efficiencies, the bilayer of BCP/CBP shows increased thermal stability of device than the monolayer of BCP, mostly because upper CBP thin film stabilizes under BCP thin film. The mixed layer of BCP:CBP gives slightly decreased efficiency than BCP and BCP/CBP, mostly because the electron mobility of the OSC using BCP:CBP is decreased than those using BCP and BCP/CBP. However, the BCP:CBP increases thermal stability of device than BCP and BCP/CBP, ascribed to that the BCP and CBP effectively inhibit reciprocal tendencies of crystallizations in the mixed layer. Moreover, the BCP:CBP improves the light stability of device than the BCP and BCP/CBP, because the energy transfer from BCP to CBP in in the mixed layer effectively decelerates the photodegradation of BCP. We provide a facial method to improve the stabilities of cathode buffer layers against heat and light, beneficial to the commercial development of OSCs.