Synergistic Self‐Assembled Monolayers Reinforce Buried Interface Anchoring for High‐Efficiency Tandem Perovskite Solar Cells

We developed a synergistic self-assembled monolayer (syn-SAM) strategy by blending a non-planar molecule ABT with the commonly used Me-4PACz SAM. 1.56 eV single-junction PSCs achieved a maximum PCE of 25.75% (certified 25.45%). This approach is also beneficial for monolithic perovskite/silicon tandem solar cells based on fully textured HJT silicon bottom cells, achieving record PCEs of 31.56% (area: 1.07 cm²) and 26.57% (area: 20.06 cm²).

Abstract

Carbazole-based self-assembled monolayers (SAMs) have been commonly used as a single-component hole transport layer (HTL) in inverted perovskite solar cells (PSCs), but suffer from facile π-π stacking and self-aggregations in solution and consequently poor anchoring ability with the atop perovskite layer. Herein, we developed a synergistic SAM (syn-SAM) strategy through blending a non-planar molecule 3,3-(4-amino-4H-1,2,4-triazole-3,5-diyl)-dibenzo acid (ABT) bearing multiple anchoring sites with the commonly used Me-4PACz SAM. The coexistence of these two components leverages π-π interactions and hydrogen bonding to mitigate aggregation effects, affording dense and uniform SAM, thereby enhancing anchoring at the perovskite buried interface and alleviating interfacial charge recombination. ABT incorporation further helps to mitigating tensile strain in perovskite film. Additionally, this strategy offers advantages of multi-device compatibility. The single-junction champion inverted PSC devices based on syn-SAM deliver power conversion efficiencies (PCEs) of 25.75% (certified 25.45%) and 22.76% (area: 0.105 cm²) for 1.56  and 1.68 eV bandgap perovskites, respectively. Moreover, this approach is beneficial for the monolithic perovskite/silicon tandem solar cells based on fully textured surfaces of heterojunction (HJT) silicon bottom cells, affording PCEs of 31.56% (area: 1.07 cm²) and 26.57% (area: 20.06 cm²). All devices exhibit excellent long-term storage and thermal stability even under non-encapsulated conditions.

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