Cu2−xGeS3: a new hole transporting material for stable and efficient perovskite solar cells

Abstract

Cu_2−xGeS₃ is a kind of inorganic semiconducting compound with earth abundant elemental storage, excellent chemical stability and environmentally friendly characteristics. It has been used as a light absorption material in traditional p–n junction thin film solar cells. This research presents that Cu_2−xGeS₃ can also serve as a highly efficient hole transporting material for perovskite solar cells with enhanced stability. The results show that perovskite solar cells based on the Cu_2−xGeS₃ film can retain 95% power conversion efficiency when exposed to 50% relative humidity for 30 days in air under room lamp light irradiation, while the device using spiro-OMeTAD as the hole transporting material degrades considerably in 2 days and nearly completely degrades in 10 days. Mechanistic investigation shows that the inherent stability and hydrophobic nature of the Cu_2−xGeS₃ film contribute to the enhanced moisture stability. This investigation provides a material choice for high-efficiency perovskite solar cells with enhanced moisture stability.