Broadband all-polymer photodetectors with ultrahigh detectivity above 1014 Jones enabled by fine-tuned molecular stacking via facile random terpolymerization

All-polymer photodetectors (all-PPDs) show great potential in the next generation of electronic devices. In order to achieve stable high-performance all-PPDs, the balance between the ordered molecular stacking of a single polymer and the miscibility of donor/acceptor is a key issue. N2200 is a typical acceptor polymer with excessive self-aggregation, and regulating the molecular stacking rationally of N2200 is still challenging. Herein, we demonstrate a facile approach of terpolymerization to solve the dilemma by introducing the small amount of ITIC unit as a "crystal defect" into over self-assembled N2200 to synthesize a new terpolymer NTI. Compared with N2200, NTI shows higher light absorption coefficient and higher LUMO energy level. Notably, the crystallinity of NTI and the miscibility of J71/NTI are remarkably balanced, leading to better film morphology and more balanced carrier mobility of the active layer. Therefore, the J71:NTI device features an ultrahigh specific detectivity (D*) of 1.2 × 1014 Jones, a fast response speed of 1.31/2.50 μs, and a large linear dynamic range of 105 dB under −0.1 V bias. To our knowledge, it is the highest D* for all-PPDs reported. Furthermore, J71:NTI device shows better spectral response stability over 30 days and was successfully applied as the human real-time blood oxygen signal monitor. This work demonstrates a facile approach to balance the ordered molecular stacking and the miscibility enabling stable high-performance all-PPDs.