Achieving efficient organic solar cells: Via synergistically doping active layers and interfaces by a conjugated macrocycle

To facilitate the device optimization of organic solar cells, a conjugated macrocycle, namely cyanostar, has, for the first time, been utilized to simultaneously modify the active layer and hole transporting layer. Benefiting from the sequential deposition technology, cyanostar is able to percolate into the underlying PEDOT:PSS and the upper active layer, while a transition layer enriched with cyanostar is formed as well. Owing to the positively charged hydrogens and the low-lying energy levels, cyanostar can simultaneously p-dope the PEDOT:PSS layer and polymer donor. Such doping effect can prolong the carrier lifetime, suppress charge recombination, and promote charge transport and extraction. Moreover, cyanostar positively or negatively affects the morphology depending on its distribution in the active layer due to the different miscibility. Based on the synergistic effects of cyanostar, the champion device achieves a power conversion efficiency of 17.98%. Cyanostar is also applicable in varying donor/acceptor combinations. This work paves the way to employ conjugated macrocycles as versatile additives in organic solar cells.