Dual Interface Modification Using Potassium Aspartic Acid to Realize Low Dark Current, High-Speed Nonfullerene Photodetectors

Organic photodetectors (OPDs) have attracted tremendous interest due to their potential applications in wearable electronics. However, due to the nonideal contacts between the electrodes and organic semiconductors, OPDs still suffer from high dark current and slow frequency response. Herein, by inserting potassium aspartic acid (PAA) interlayers between ITO/metal oxides and the metal oxides/active layer, the shunts and hole injections are blocked and the energy levels of the electrodes are aligned. As a result, our dual-interface modified OPDs (ITO/PAA/ZnO/PAA/PTB7-Th:ITIC/MoO3/Ag) exhibit suppressed dark current 550 times lower than the reference device, corresponding to specific detectivity of 2.1 × 1012 Jones, broad linear dynamic range of 113 dB, and quick response time to the nanosecond level. PAA interlayers have also been demonstrated to improve the storage stability of OPDs, leading to 10 times slower degradation for the on/off ratio when compared with the reference and conventional polyethylenimine-modified OPDs.