Lattice‐Selective Cross‐Interface Bidentate Passivation for Efficient Bifacial Tandem Carbon‐Based Perovskite Solar Cells

For printable mesoscopic perovskite solar cells (p‐MPSCs), the formation of numerous grain boundaries due to the microstructural confinement of mesoporous materials is a key factor that leads to concentrated defects and limits intercrystalline charge transport. Herein, the electron‐donating and electron‐withdrawing effects of atoms are harnessed, respectively, and a unique molecular configuration with alternating distributions of sulfur atoms in thieno[3,2‐b]thiophene to construct a cross‐interface bidentate passivation molecule, 2,5‐dibromothiophene [3,2‐b] thiophene (TT‐2Br), is utilized. By exploiting its lattice's selective matching, efficient chelation with undercoordinated lead ions, bridging crystal boundaries, is achieved. Furthermore, to overcome the limitation of nonlayered assembly caused by the carbon electrode's full light absorption in p‐MPSCs, an artificial reflector device to achieve dual‐sided four‐terminal tandem assembly with TT‐2Br serving as the small‐molecule interfacial passivating agent is used. This approach significantly improves the bifacial power output (BPO) to 20.44 mW cm −2 and the open‐circuit voltage to 2.03 V in series‐connected devices. In parallel‐connected devices, the BPO increases to 25.84 mW cm −2 , and the short‐circuit current reaches 39.96 mA cm −2 . This innovative strategy effectively addresses the challenges of interfacial passivation and layered assembly in p‐MPSCs.