New Nitrogen‐Containing Heterocyclic Non‐Fullerene Electron Acceptor as Guest in PBDB‐T:Y6 Blends for Air‐Processed Ternary Organic Solar Cells with Efficiency Approaching 16%

A new non‐fullerene small‐molecule acceptor (NFSMA), designated as TDPT‐TBA , is synthesized. This molecule is based on an S,N‐heteroacene central core connected to a weakly electron‐withdrawing end group, 1,3‐diethyl‐2‐thiobarbituric acid. In these findings, it is suggested that incorporating an sp 2 ‐hybridized nitrogen atom into a fused cyclopentadiene framework, rather than utilizing a sp 3 ‐hybridized carbon atom, can lead to a more effective NFSMA and potentially enhance the performance of organic solar cells. The TDPT‐TBA exhibits an upshifted lowest unoccupied molecular orbital energy level of −3.76 eV when compared to the Y6 acceptor. Additionally, there are complementary absorption spectra between both the polymer Poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′] dithio‐phene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))] (PBDB‐T) and Y6. Organic solar cells utilizing the PBDB‐T:TDPT‐TBA blend achieves a high open‐circuit voltage of 0.942 V, yielding a power conversion efficiency (PCE) of 13.72%. When TDPT‐TBA is incorporated into a PBDB‐T:Y6 binary active layer, the optimized ternary organic solar cells reach a PCE of 16.06%, surpassing the efficiency of the binary PBDB‐T:Y6 configuration, which is 13.51%, under identical processing conditions. The increase in PCE can be attributed to several factors, including the utilization of excitons generated in TDPT‐TBA via energy transfer to Y6, a longer charge carrier lifetime, shorter charge extraction times, increased crystallinity, and denser stacking distance. These factors collectively contribute to reduced carrier recombination and improved charge transport.