Simultaneous bottom-up double-layer synergistic engineering by multifunctional natural molecules for efficient and stable SnO2-based planar perovskite solar cells

Abstract

The performance and stability of perovskite solar cells (PSCs) is limited by detrimental defects, mostly distributed at the grain boundary (GB) of bulk perovskite film and interface, which induce serious carrier non-radiative recombination. Therefore, there is particularly urgent to realize simultaneous passivation of bulk defects and interfacial defects. In this work, a simple, low-cost and effective multifunctional modification strategy is developed by introducing the λ-Carrageenan (λ-C) as the interfacial layer of SnO2/perovskite. The sulfate groups of λ-C not only play a positive role in passivating the Sn4+ from SnO2 film, resulting in high conductivity, but also effectively passivate the defects at the SnO2/perovskite interface. Meanwhile, λ-C can effectively passivate the defects in the perovskite film due to the strong binding force between the high content of sulfate groups and PbI2. The synergistic effect of λ-C simultaneously achieves interfacial defects and bulk defects passivation, better crystalline quality, suppressed charge recombination, released interfacial stress and more favorable interfacial energy level alignment. Based on the above efficient synergy, the λ-C-modified device achieves a high efficiency of 23.81%, which is ∼24.53% higher than the control device (19.12%). To our best knowledge, 23.81% of power conversion efficiency (PCE) is the highest reported PCE value of PSCs employing green natural additives. Moreover, long-term and thermal stabilities are significantly improved after interface modification. Thus, this work provides an idea for developing multifunctional natural materials towards the attainment of the efficient and stable PSCs.