Fast Photoresponse from Hybrid Monolayer MoS2/Organic Photodetector

As a direct-bandgap transition semiconductor with high carrier mobility, monolayer (ML) transition metal dichalcogenides (TMDCs) have attracted significant attention as a promising class of material for photodetection. It is reported that these layers exhibit a persistent photoconductance (PPC) effect, which is assigned to long-lasting hole capture by deep traps. Therefore, TMDCs-based photodetectors show a high photoresponse but also a slow response. Herein, intensity-modulated photocurrent spectroscopy (IMPS) with steady-state background illumination is performed to investigate the photoresponse dynamics in a hybrid photodetector based on ML MoS2 covered with an ultrathin layer of phthalocyanine (H2Pc) molecules. The results demonstrate that adding the H2Pc layer speeds up the photoresponse of the neat ML-MoS2 photodetector by almost two orders of magnitude without deteriorating its responsivity. The origin of these improvements is revealed by applying the Hornbeck-Haynes model to the photocarrier dynamics in the IMPS experiment. It is shown that the improved response speed of the hybrid device arises mostly from a faster detrapping of holes in the presence of the H2Pc layer, while the trap densities remain rather unchanged. Meanwhile, the additional absorption of photons in the H2Pc layer contributes to photocarrier generation, resulting in an enlarged responsivity of the hybrid device.

Automated summary

Monolayer transition metal dichalcogenides (TMDCs) are highly promising materials for photodetection due to their high carrier mobility and direct-bandgap transition semiconductor properties. However, TMDCs-based photodetectors have a slow response time due to persistent hole capture. This study investigates the photoresponse dynamics of a hybrid photodetector incorporating an ultrathin layer of phthalocyanine (H2Pc) molecules on ML MoS2 using intensity-modulated photocurrent spectroscopy (IMPS). The addition of the H2Pc layer significantly improves the response speed and responsivity of the photodetector by enhancing hole detrapping and increasing photon absorption.