Flexible perovskite/silicon tandem solar cell with a dual-buffer layer.

Perovskite/silicon tandem solar cells have emerged as promising candidates for next-generation photovoltaic technology owing to their ultrahigh power conversion efficiency (PCE)1-3. However, the mechanical stress generated during repeated environmental stress cycles remains a critical challenge for flexible perovskite/silicon tandem solar cells, leading to interfacial delamination and device degradation. Here we propose a dual-buffer-layer strategy with a stress-release mechanism to synergistically mitigate ion bombardment during subsequent sputtering deposition and enhance interfacial adhesion while preserving efficient charge extraction. The loose SnOx buffer layer, engineered by adjusting the purging time of atomic layer deposition (ALD), can dissipate strain energy, whereas the compact SnOx layer can ensure robust electrical contact. On the basis of this dual-buffer layer, the flexible tandem solar cell, constructed on a 60-micron-thick ultrathin silicon bottom cell, achieves a certified PCE of 33.4% on 1-cm2 area and a certified PCE of 29.8% on a wafer-sized area of 260-cm2 with a power-per-weight of up to 1.77 W g-1. The modified tandem solar cells demonstrate good durability, retaining more than 97% of their initial PCEs after 43,000 bending cycles under a maximum curvature radius of around 40 mm in air and around 97% after thermal cycling testing (-40 °C to 85 °C) for 250 cycles.