Multilayer structure boosts photodetector performance

Researchers at Princeton University (Princeton, NJ) have used a multilayer stack structure to increase the bandwidth and quantum efficiency obtainable with organic photodetector materials to approximately 430 MHz and 75%, respectively. The active regions of their devices consisted of alternating layers of copper phthalocyanine (CuPc) and 3,4,9,10-perylenetertracarboxylic bis-benzimidazole grown on top of a transparent, 1500-Å-thick indium tin oxide anode atop a glass substrate. The CuPc layer was grown first atop the anode, and the entire layer-structure thickness was 320 Å. The number of layers, however, varied from two layers, each occupying half the thickness, to 64 layers that were 5 Å thick. The construction of photodetectors based on small-molecule multilayer organic thin films provided the high-performance results by facilitating the transport of photogenerated charge carriers to the electrodes prior to the occurrence of recombination or deep-charge trapping. The researchers expect devices based on this technology to find use in high-speed and large-area imaging applications in the visible and near-infrared spectral regions. Contact Stephen Forrest at [email protected].