Regular Article

Comparative study on thermally evaporated and solution processed cathode modifying layers in organic solar cells^★

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: qindashan06@aliyun.com

Received: 2 May 2022
Received in final form: 24 May 2022
Accepted: 7 June 2022
Published online: 30 August 2022

Abstract

Organic solar cells have been fabricated using cathode modifying layers of thermally evaporated bathophenanthroline (Bphen), ytterbium doped Bphen (Bphen:Yb), and solution processed (N,N-dimethyl-ammonium N-oxide) propyl perylene diimide (PDINO). Compared to pristine Bphen, Bphen:Yb shows higher electron mobility and thereby increases fill factor of device, demonstrating the weak n-doping of Yb in Bphen. As a result of Fermi level pinning, Bphen:Yb forms an ohmic contact with photoactive layer, underpinning efficient electron injection and extraction of device. Compared to conventional PDINO, despite lower electron mobility, Bphen:Yb enables increased optical absorption of device and smoother morphology of device, thereby improving power conversion efficiency of device. The current research points out that the integration of thermally evaporated weakly n-doped cathode modifying layer and solution processed photoactive layer is a promising method to fabricate high-efficiency and low-cost organic solar cells.