Synergistic transition metal ion co-doping and multiple functional additive passivation for realizing 25.30% efficiency perovskite solar cells

Abstract

The carrier extraction and transportation capability of electron-selective layers and light-absorbers are very important for achieving highly efficient perovskite solar cells (PSCs). Herein, a holistic approach to boost the carrier transportation in a SnO₂/perovskite stack is presented. First, the optoelectronic properties of SnO₂, such as carrier mobility, conductivity, energy levels and trap states, are effectively regulated via a Nb⁵⁺ and Ta⁵⁺ co-doping strategy (denoted as NT:SnO₂). Meanwhile, the upgraded SnO₂ modulates the subsequent crystallization of perovskites, resulting in enhanced crystallinity. Second, a multifunctional molecule of 4,4′-dithiodibutyric acid is selected to further passivate the charged-traps in perovskites, leading to significantly decreased non-radiative recombination and an increased carrier lifetime of over 3 μs. Finally, the champion device consisted of NT:SnO₂ and the optimized perovskite film delivered an impressive PCE of 25.30% along with a high fill factor of 84.51%, which is among the highest efficiencies for RbCsFAMA-based PSCs to date. The target device without encapsulation also shows excellent long-term operational stability, over 90% of its initial efficiency is retained after 1200 h of continuous maximum output power point tracking under 1 sun illumination. This study will pave a new avenue for managing the carrier behavior in a SnO₂/perovskite stack and realizing highly efficient and stable PSCs.