Reducing the efficiency–stability–cost gap of organic photovoltaics with highly efficient and stable small molecule acceptor ternary solar cells

We demonstrate highly efficient and stable solar cells using a ternary approach, wherein two non-fullerene acceptors are combined with both a scalable and affordable donor polymer, poly(3-hexylthiophene), and a high efficiency, low band-gap polymer in a single-layer bulk-heterojunction devices

Derya Baran


Scholarcy highlights

  • Technological deployment of organic photovoltaic modules requires improvements in device light-conversion efficiency and stability while keeping material costs low
  • We have recently shown that solar cells using an alternative small molecule non-fullerene acceptor, IDTBR, when mixed with P3HT, can achieve power conversion efficiencies of up to 6.4%
  • The combination of stability, cost and performance for P3HT:NFA devices, make them a compelling choice for commercialization of organic photovoltaics compared to devices using fullerenes, for which the high costs and energy involved are prohibitive for large scale production
  • Through optimizing the acceptor phase loading ratio in a D:A1:A2 blend, and molecular packing with respect to the binary blend, we demonstrate a concurrent improvement in Jsc, Voc and FF resulting in a power conversion efficiency of 7.7± 0.1% % for P3HT cells
  • Characterization of neat materials and blends Previously, we have shown that a NFA containing an indacenodithiophene core flanked with benzothiadiazole and rhodanine groups, named IDTBR, can deliver 6.4% PCE in a solar cell device when combined with P3HT, which is the highest P3HT:NFA performance reported
  • Further addition of IDFBR resulted in Voc values of 0.82 V, but a decrease in Jsc, which is mainly attributed to the reduced absorption at long wavelengths from IDTBR in the ternary blend
  • The high efficiency PCE10:PC70BM device performance dropped to 20% of its initial value. These results suggest that the addition of IDFBR to P3HT:IDTBR blend improves photovoltaic performance and has a synergistic benefit to both storage lifetime and photo-stability, which demonstrates a significant advantage for practical applications in comparison to low band gap:fullerene solar cells
  • All ternary devices were processed using chlorobenzene without further processing or solvent additives and active layers were pre-annealed in inert atmosphere at 130 °C for 10 min, which is required for P3HT crystallization. Current density-voltage characteristics were measured in both forward and backward directions at room temperature, with 20 mA/s scan speed in air, using a Xenon lamp at AM1.5 solar illumination calibrated to a silicon reference cell with a Keithley 2400 source meter, correcting for spectral mismatch

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