Retarding Phase Segregation via Lattice Reinforcement for Efficient and Stable Perovskite/Organic Tandems

Abstract The operational perovskite/organic tandems are subjected to light irradiation and driven by a higher bias voltage than single‐junction solar cells, posing a severe challenge to their stabilities. Light irradiation can trigger halide phase segregation in the perovskite subcell, exacerbated under higher bias voltage through electron–phonon coupling. To address this, dimethylammonium ion (DMA + ) incorporation delays perovskite crystallization by forming an intermediate phase, enhancing crystallinity, and reducing lattice structural defects. DMA + with a larger ionic radius entering the A‐site of lattice tilts the [PbX 6 ] 4− (X: I or Br) octahedral, enlarging the perovskite bandgap, shortening Pb─I bonds, and reinforcing the lattice. This mitigates halide escaping from the lattice and subsequent ion migration. Phase segregation in the perovskite subcell is significantly suppressed under high‐power irradiation and bias voltage. Consequently, the perovskite subcell exhibits increased and stable quasi‐Fermi‐level splitting values, delivering a high open‐circuit voltage of 1.34 V. Notably, 0.062‐cm 2 and 1.004‐cm 2 perovskite/organic tandems achieved remarkable efficiencies of 26.15% (certified of 25.34%) and 24.87%, respectively, exhibiting excellent operational stability of T 90 ∼ 1350 h.