Blade printing of low-melting-point alloys as back electrodes for high-efficiency and stable inverted perovskite solar cells†

Printing of electrodes to replace thermal evaporation of metals for back contacts in perovskite solar cells (PSCs) is essential for scalable manufacturing. However, PSCs incorporating printed electrodes typically exhibit lower power conversion efficiencies (PCEs) than those with evaporated metals. Low-melting-point alloys (LMPAs) are promising candidates for PSC electrodes due to their matched work functions, high electrical conductivities, and chemical stability. This study proposes a convenient strategy of blade printing to pattern In–Sn–Bi LMPAs as back electrodes in inverted PSCs. These LMPAs, with moderate melting points (62 °C, 80 °C, and 120 °C), are printed above their melting points and solidify at room temperature without additional post-treatment. PSCs with LMPA electrodes show high built-in potential and fast charge extraction, achieving PCEs of 22.48%, comparable to their evaporated-metal counterparts. Charge transport and recombination dynamics reveal that PSCs with LMPA electrodes are more stable than those with evaporated copper electrodes after aging in air without encapsulation. Morphological analysis of LMPAs and perovskite layers after aging shows no noticeable corrosion. PSCs with blade-printed LMPA electrodes retain ∼80% of their peak PCE after 1500 hours of aging, demonstrating significantly higher stability than PSCs with evaporated copper or silver electrodes.