Study on the influence of hole transport materials on the response speed of organic photodetectors by time-of-flight technique

Abstract

Organic photodetectors (OPDs) offer some advantages, including flexibility, cost-effectiveness, wavelength tunability, and lightweight, making them compelling alternatives to inorganic photodetectors across numerous applications. However, the low charge carrier mobility of organic semiconductors greatly limits the response speed of OPDs, which remains a significant challenge to further enhance the response speed of these devices to meet the demands of communication and other fields. Previous studies have mainly focused on the efforts to enhance the response speed, but the relationship between response speed and charge carrier transport characteristics has been rarely explored. In this study, we employ the time-of-flight technique to investigate the mobility characteristics of different hole transport layer materials, MCBP and TCTA, and their impact on response speed of the resulting OPDs. The OPD utilizing TCTA as the hole transport layer has achieved a -3dB bandwidth of up to 85 MHz. Compared with MCBP with higher mobility, the stronger transport dispersion of TCTA makes it a more suitable choice for fast-response OPDs, suggesting that the response speed is not solely determined by the mobility of charge carrier transport layer materials.