Efficiency exceeding 20% in perovskite solar cells with side-chain liquid crystalline polymer–doped perovskite absorbers

Attaining high quality perovskite films with enhanced morphology, high efficiency, and better stability is a great research challenge. Here, a side-chain liquid crystalline polymer (SCLCP) is incorporated as a dopant into the perovskite film to achieve perovskite solar cells (PSCs) with high efficiency and long-term stability. SCLCP doping increases the grain size in the crystalline perovskite film by controlled solvent evaporation and reduced grain boundaries, which slow the material degradation and reduce the charge recombination. Using this approach, the PSC power conversion efficiency (PCE) is significantly boosted from 18.0% (nondoped) to 20.63% for the SCLCP-doped perovskite film with much improved air stability. Furthermore, the trap state density in the SCLCP-doped films is decreased because the SCLCP effectively passivates the perovskite grain surface. Notably, the SCLCP appears to act as a bridge between grains for effective charge transfer from perovskite toward the electrode, which would partially explain the enhanced efficiency and stability.