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

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 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.