Solution synthesis of GeS and GeSe nanosheets for high-sensitivity photodetectors†
We report the synthesis of 2D nanosheets of GeS and GeSe by facile solution based approaches. The synthesized nanosheets are single-crystalline in nature with lateral dimensions in micrometers. Band structures calculated from DFT calculations predicted a direct bandgap value of 1.67 and 1.37 eV for GeS and GeSe, respectively. The experimental bandgap values (GeS, Eg = 1.6 eV and GeSe, Eg = 1.2 eV) determined from optical measurements are slightly smaller than the predicted ones. Photoresponse measurements of GeS and GeSe nanosheets revealed that the nanosheets are extremely photoresponsive toward the incident light and exhibit a high photoresponsivity of up to 173 and 870 A W−1 under a 405 nm laser diode, respectively. These values are several orders of magnitude higher than those of previous reports for graphene and many other metal chalcogenide nanosheet photodetectors. In addition, the photodetectors show a fast photoresponse time and a specific detectivity on the order of 1013 Jones. These results show that both the GeS and GeSe nanosheets are promising narrow bandgap semiconductors for high performance photodetectors.