Efficient thick film non-fullerene organic solar cells enabled by using a strong temperature-dependent aggregative wide bandgap polymer

In this work, a temperature-dependent aggregative polymer (PBDT-DTBTO) has been successfully explored to realize efficient thick film organic solar cells (OSCs). PBDT-DTBTO possesses a deep HOMO energy level of -5.35 eV and a wide bandgap of 1.76 eV, which is complementary to the near-infrared absorption of the paired non-fullerene acceptor, INPIC-4F. We reveal the efficacy of the temperature-dependent aggregative PBDT-DTBTO/INPIC-4F bulk-heterojunction (BHJ) blend for thick film OSCs through tuning the processing solvent and thermal annealing temperature. The results show that the device using chlombenzene as the processing solvent only yields a mediocre power conversion efficiency (PCE) of 8.69%. Whereas, a superior PCE of 13.1% can be achieved by using chloroform (CF) as the processing solvent and proper thermal annealing. The morphological analysis shows that the bicontinuous network of the PBDT-DTBTO/INPIC-4F BHJ blend possesses a preferential face-on orientation when using CF as the processing solvent and thermal annealing, resulting in suppressed charge recombination and superior charge transport in the derived device. Moreover, the PBDT-DTBTO/INPIC-4F-based OSC demonstrates a high thickness toleration of the BHJ layer, which can still deliver a high PCE of 12.6% while the thickness of the BHJ layer is increased to similar to 320 nm. More encouragingly, a promising PCE of over 12% can also be achieved for the device fabricated by blade-coating, revealing its great potential for the high-throughput solution-coating process.

Automated summary

By utilizing the temperature-dependent aggregative polymer PBDT-DTBTO in combination with the non-fullerene acceptor INPIC-4F, the efficiency of thick film organic solar cells has been significantly improved by optimizing the processing solvent and thermal annealing conditions. The unique bicontinuous morphology and face-on orientation of the PBDT-DTBTO/INPIC-4F blend, achieved through the use of chloroform as the processing solvent and proper thermal annealing, lead to enhanced charge transport and reduced charge recombination, resulting in high power conversion efficiencies.