Regular Article

Determining the exciton diffusion length of copper phthalocyanine in operating planar-heterojunction organic solar cells

¹ Hebei Key Laboratory of Functional Polymers, School of Chemical Engineering, Hebei University of Technology, Tianjin 300130, P.R. China
² Tianjin key laboratory of chemical process safety, School of chemical engineering, Hebei university of technology, Tianjin 300130, P.R. China
³ Department of Electrical and Computer Engineering, University of Waterloo, 200 University Ave. West, Waterloo, ON, N2L 3G1, Canada

^* e-mail: qindashan06@aliyun.com

Received: 1 November 2019
Received in final form: 5 January 2020
Accepted: 4 March 2020
Published online: 6 May 2020

Abstract

Organic solar cells based on planar copper phthalocyanine (CuPc)/C₆₀ heterojunction have been characterized, in which a 2 nm-thick layer of bathocuproine (BCP) is inserted into the CuPc layer. The thin layer of BCP allows hole current to tunnel it through but blocks the exciton diffusion, thereby altering the steady-state exciton profile in the CuPc zone (zone 1) sandwiched between BCP and C₆₀. The short-circuit current density (J_SC) of device is limited by the hole-exciton scattering effect at the BCP/CuPc (zone 1) interface. Based on the variation of J_SC with the width of zone 1, the exciton diffusion length of CuPc is deduced to be 12.5–15 nm. The current research provides an easy and helpful method to determine the exciton diffusion lengths of organic electron donors.