Bulk-Heterojunction Photovoltaic Cells with Donor–Acceptor Ratio Varied across the Film Prepared by Evaporative Spray Deposition Using Ultradilute Solution Method

Abstract

We fabricated three types of bulk-heterojunction (BHJ) photovoltaic cells with the electron donor and acceptor ratio varied across the film. One has a stacked layer structure of a donor-rich layer (2:1) the near cathode and an acceptor-rich layer (1:2) near the anode (DA-BHJ), another has a stacked structure with the inverse order (AD-BHJ), and the other has a constant ratio (1:1) as a reference. These were fabricated by evaporative spray deposition using ultradilute solution (ESDUS) method. The DA-BHJ cell showed significantly higher energy conversion efficiency than the AD-BHJ cell and the reference BHJ cell where the three exhibited almost identical light absorption.