Efficient 1.77 eV-bandgap perovskite and all-perovskite tandem solar cells enabled by long-alkyl phosphonic acid

Incorporating dodecylphosphonic acid additives into 1.77 eV-bandgap perovskites enabled single-junction solar cells to achieve a PCE of 20.2%. Tandem cells further reached impressive PCEs of 27.41% (two-terminal) and 28.65% (four-terminal).