Multi‐Functional Semiconductor Polymer Doped Wide Bandgap Layer for All‐Perovskite Solar Cells with High Efficiency and Long Durability

Abstract The study presents a multi‐functional and semiconductor polymer poly[bis(3‐hexylthiophen‐2‐ yl )thieno[3,4‐ c ]pyrrole‐4,6‐dione] (PBDTTPD) doping strategy that significantly enhanced the performance of the two‐terminal all‐perovskite tandem perovskite solar cells (T‐PSCs). An optimized power conversion efficiency (PCE) of 26.87% has been achieved. The incorporation of PBDTTPD into the wide bandgap (WBG) perovskite layer evidently improved its crystallinity and enhanced the top‐cell's PCE to 18.49%. After 2880 h dark storage in nitrogen, the TPSC retained 87.4% of initial PCE, which demonstrates the device's stability. On flexible polyethylene‐naphthalate (PEN) substrate, the TPSC achieved an enhanced champion PCE of 22.96%, and significantly advanced anti‐bending ability. The TPSC's enhanced performance is ascribed to the strong coordinate‐bonding between the S/N/O passivation sites in PBDTTPD, and the Pb ²⁺ defects in the WBG perovskite layer's grain boundaries. Optoelectronic simulations demonstrated a 23%‐24% theoretical PCE limit for the WBG single‐junction PSCs with ≈1.8 eV bandgap. To boost the PCE of next‐generation TPSCs, it is crucial to further mitigate both the bulk and the surface recombination.