Development of Photoactive and Interfacial Materials for Non-fullerene Acceptor-based Organic Solar Cells

Abstract

Organic solar cells (OSCs) have emerged as a renewable energy application such as wearable photovoltaics, building-integrated photovoltaics (BIPVs), and agrophotovoltaics (APVs) due to their color-tunability, semi-transparency, lightweight, and flexibility. Because of these advantages of OSCs, research has been steadily continued despite the low efficiency compared to the inorganic solar cells. Moreover, with the development of new photoactive materials such as non-fullerene acceptors, power conversion efficiency (PCE) has also increased rapidly in these days. However, there are several issues must be overcome for commercialization of OSCs: efficiency, stability and scalability. In this study, I proposed a method to improve PCE and photostability of OSCs by the development of photoactive and interfacial materials. First, to achieve high PCE, I designed new electron-donating conjugated polymers to improve open-circuit voltage (VOC) by substituting the alkyl side chain of thiophene with the alkylthio groups. Then I confirmed that the VOC of the devices was increased when the amount of alkylthio group increased. Second, to enhance the photostability of the OSCs, I introduced wide bandgap metal oxide to suppress the photocatalytic effect. As a result, by using wide bandgap (324 nm) titanium suboxide (TiOX), I achieved photostable (PCE drop 20% after 145 h under 1 sun illumination) OSCs without any encapsulation and filter.