How do carbon dots with amine terminals help perovskite solar cells perform better?

Lead halide perovskite solar cells can be significantly improved with multifunctional additives such as carbon dots (CDs) with amine terminals via defect passivation and band alignment. Here, we determine rational guidelines for the usage of such quantum dots in perovskite solar cells by systematically studying their effects on crystal quality and carrier transport. The amine-terminated CDs homogeneously dispersed in precursors improve the crystal quality of perovskite films, but they reduce the hole mobility hampering hole extraction. In contrast, CDs deposited between the electron transport layer and active layer could promote spin-coated film quality and electron's extraction efficiently. So, the approaches of the carbon dots in device alters semiconductor properties and energy level structure. Interface engineering achieve better crystal quality and energy level alignment, which in turn affects charge collection, thereby increasing current density and power conversion efficiency. According to the findings of this study, when considering defect passivation by additives, the energy band alignment of the device should also be considered, since this could change carrier dynamics and device performance differently. [Display omitted] • Based on the effects of amine-terminated carbon dots, a rational guideline for the use of such CDs in perovskite solar cells was determined. • Carbon dots are able to passivate grain boundaries, optimize device interfaces, improve film morphology, align energy levels, and enhance carrier mobility. • The CDs homogeneously dispersed in precursors improve the crystal quality of perovskite films, but they increased energy barrier and hampered hole extraction. • The interface engineering via depositing the CDs between the electron transport layer and the active layer improves film quality and promotes electron extraction. • The interface engineering suggested comprehensive improvements over the precursor engineering, thereby leading to current density and power conversion efficiency changes. [ABSTRACT FROM AUTHOR]