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 SnO_x buffer layer, engineered by adjusting the purging time of atomic layer deposition (ALD), can dissipate strain energy, whereas the compact SnO_x 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.