The charge transport and morphology of active layers are key considerations for device performance and stability in organic solar cells (OSCs). Such properties can be fine-tuned via elaborate molecular design of fused-ring electron acceptors (FREAs), especially conjugation extension and side chain engineering. In this work, N-functionalized conjugation is explored in the design of high-efficient asymmetric FREAs. The twisting of N-conjugated side chains from backbone endows three FREAs with similar energy levels and light absorptions (≈850 nm edge). Their blends with PBDB-T exhibit high charge carrier mobility and ordered phase separation. Excitingly, IPT2F-TT based OSCs yield a champion power conversion efficiency (PCE) of 14.02% with a fill factor (FF) of 75.06%, outperforming PBDB-T devices with IPT2F-Th (12.52%, 71.20%), IPT2F-Ph (13.13%, 72.11%), and octylated IPT-2F (13.70%, 71.50%). The PCE over 14% and FF over 75% are among the highest values for 2D FREAs OSCs reported to date. More importantly, outstanding thermal stability and light soaking stability are observed with PCE over 12% maintained after thermal or light aging for 100 h. This work demonstrates N-conjugated FREAs design as an effective strategy to simultaneously improve the photovoltaic performance and device stability for the OSCs.
Organic solar cells based on a nonacyclic carbazole-cored non-fullerene acceptor exhibited a high power conversion efficiency of 12.07% with enhanced stability.
In
this study, an efficient ternary bulk-heterojunction (BHJ) organic
solar cell (OSC) is demonstrated by incorporating two acceptors, PC61BM and ITC6-4F, with a polymer donor (PM6). This reveals
that the addition of PC61BM not only enhances the electron
mobility of the derived BHJ blend but also facilitates exciton dissociation,
resulting in a more balanced charge transport alongside with reduced
trap-assisted charge recombination. Consequently, as compared to the
pristine PM6/ITC6-4F device, the optimal ternary OSC is revealed to
deliver an improved power conversion efficiency (PCE) of 15.11% with
a boosted J
SC, V
OC, and fill factor (FF) simultaneously. The resultant V
OC and FF are among the highest values recorded
in the literature for the ternary OSCs with a PCE exceeding 15%. This
result thus suggests that besides improving the charge transport characteristics
in devices, incorporating a fullerene derivative as part of the acceptor
can also improve the resultant V
OC, which
can reduce the energy loss to realize efficient organic photovoltaics.
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