ACS Applied Electronic Materials
Processes Controlling the Distribution of Vertical Organic Composition in Organic Photodetectors by Ultrasonic-Assisted Solvent Vapor Annealing
Dayong Zhang, Dan Zhao, Zijun Wang, Junsheng Yu
Regulating the vertical composition distribution of an organic electronic donor and acceptor is an effective strategy for the fabrication of high-performance organic photodetectors (OPDs). In this study, after the one-step solution process to fabricate an active layer, an ultrasonic-assisted solvent vapor annealing method (UA-SVA) was proposed to modulate the vertical distribution of the PBDB-T:ITIC BHJ layer in an OPD device. Compared to the control device processed from SVA, the obtained OPD from UA-SVA exhibits both a decreased dark current and slightly enhanced photocurrent. As a result, the photodetectivity of the device treated by UA-SVA was more than one order of magnitude higher than that of the control counterpart in the detective spectrum ranging from 450 to 750 nm. Especially, a dramatically high photodetectivity of 2.17 × 1012 Jones at a wavelength of 688 nm has been achieved under a reverse bias of −0.5 V. To illuminate the reason for OPD performance improvement, ultraviolet–visible (UV–vis) absorption spectroscopy, space-charge-limited current (SCLC) method, atomic force microscopy (AFM), and water contact angle (WCA) measurement were performed, and the enhanced light-absorption intensity, improved charge carrier transport efficiency, and the modified interfacial contact and surface morphology of the BHJ active layer were observed.