Dopant-Free Planar n–i–p Perovskite Solar Cells with Steady-State Efficiencies Exceeding 18%

In this Letter, we demonstrate a planar n–i–p perovskite solar cell design with a steady-state efficiency of up to 18.8% in the absence of any electronic dopants. In the device stack, solution-processed SnO 2 is used as an electron-accepting n-type layer. The absorber layer is a perovskite with both mixed organic A-site cations and mixed halides (FA 0.83 MA 0.17 Pb(I 0.83 Br 0.17 ) 3 ). The hole-transporting p-type layer is a double-layer structure of polymer-wrapped single-walled carbon nanotubes and undoped spiro-OMeTAD. We show that this approach can deliver steady-state efficiencies as high as and even higher than those of traditionally doped spiro-OMeTAD, providing a pathway for dopant-free perovskite solar cells crucial for long-term stability.