Photovoltaic Characteristics of Inverted Bulk-Heterojunction Organic Solar Cells with Titanium Doped ZnO as their Electron Transport Layer

Abstract

Bulk-heterojunction (BHJ) organics solar cells based on conjugated polymers and fullerene derivatives with an inverted structure configuration have been fabricated using titanium doped ZnO (TiZO) as their electron transport layer (ETL). TiZO was prepared via sol gel route with 2-methoxyethanol as the solvent. In order to investigate photovoltaic characteristics and interfacial charge transfer properties, current–voltage (I-V) characterizations and electrochemical impedance spectroscopies (EIS) have been carried out. Among the samples, solar cell with 3-layers of TiZO exhibited relatively larger open circuit voltage (Voc) of about 0.55 V and higher short-circuited photocurrent density (Jsc) of about 11 mA/cm2 under AM 1.5 irradiation. Its filling factor is about 0.38 and its power conversion efficiency (CPE) is thus about 2.4%. The Nyquist plots obtained from the EIS measurements indicate that solar cells with TiZO have larger charge transfer resistance, which may be due to less trap states present in its TiZO layer.