Synergistic enhancement of charge extraction and heat dissipation in inverted perovskite solar cells via n-doped top interlayers

Thermal fatigue poses a significant challenge not only in the realm of perovskite photovoltaics, but also across various optoelectronic devices. In this study, we investigate the enhancement of both performance and stability in inverted perovskite solar cells (PeSCs) by strategically n-doping the top interlayer of a fullerene derivative (PC₆₁B-TEG) with oligoethylene glycol side chains. The n-doping of the PC₆₁B-TEG significantly enhances thermal and electrical conductivity, facilitating heat and electron extraction from the perovskite layer. In addition, the Fermi level of the PC₆₁B-TEG is upshifted by n-doping, resulting in enlarged quasi-Fermi level splitting. The incorporation of this doped interlayer leads to a notable improvement, with PeSCs achieving a maximum power conversion efficiency (PCE) of 24.42%. It also leads to an excellent improvement of thermal and photo stability retaining 90% of the initial PCE for over 2400 hours (at 85 °C and under N₂ conditions) and maintaining 80% for over 1180 hours (under continuous 1-sun illumination at 25% relative humidity), respectively. Consequently, we anticipate that the benefits of the doped interlayer will be applied to various other optoelectronic devices, making significant advances in achieving both high efficiency and stability.