Dopamine-crosslinked TiO2/perovskite layer for efficient and photostable perovskite solar cells under full spectral continuous illumination

Even though TiO2 is the most widely used electron transport layer (ETL) in high-efficiency perovskite solar cells (PSCs), ultraviolet photocatalysis and existence of intrinsic oxygen vacancies result in interfacial charge recombination and poor long-term photo-stability for TiO2-based PSC5 under full spectral continuous illumination. To solve the issues, here we report dopamine-capped TiO2 nanoparticles as ETL via chelating effect to improve interfacial binding with perovskite active layer. The introduction of dopamine can substantially reduce oxygen vacancies and suppress deep trap states within TiO2. In addition, the terminal amino groups in dopamine can passivate the uncoordinated Pb atoms and decrease the Pb-I/Br antisite defects on the interface of perovskite/TiO2. As an interfacial crosslinking agent, dopamine can not only reduce charge-accumulation and charge-recombination rate, but also increase charge-extraction efficiency at the TiO2 and perovskite interface. Based on the dopamine-capped TiO2 nanoparticles surface, the corresponding planner Cs-0.05 FA(0.81)MA(0.14)PbI(2.55)Br(0.45) PSCs deliver a power conversion efficiency of nearly 21% with negligible hysteresis. Moreover, unencapsulated devices retain 80% of their initial performance after 1200 h operation under constant full-sun illumination in nitrogen atmosphere. Ideally, this chemical-bath-deposited dopamine-modified TiO2 provides an effective commercialized route for efficient and photostable planar PSCs.