An important observation from our work with TMDC photodetectors is that under typical optical excitation conditions (irradiance between 0.4 W/cm 2 and 400 W/cm 2 ), the photoactive material does not saturate. This means that larger irradiances -either due to higher laser power or better optical focusing -invoke lower photoresistance since additional charge carriers are excited. As the RC constant of a photodetector scales directly with the photoresistance (not the resistance in the dark), increasing the irradiance is a simple yet effective means for increasing the speed of TMDC photodetectors. This becomes apparent in Figure (a) which depicts the dependence of the response time in WSe2 multilayers on the photoresistance, which is varied solely by changing the irradiance. The strong negative correlation indicates the aforementioned RC limitation, which is further verified by quantitative agreement with the calculated and fitted RC constants of the devices. Another effective means for decreasing the RC time is a reduction of the device dimensions, which lowers the resistance and capacitance simultaneously. By reducing the channel width from 25 to 20 µm (80 µm in the previous studies with substrate effects 3 ), the electrode width itself from 10 to 1 µm and the channel length from 2.5 to 1 µm, the capacitance is approximately reduced from 7.6 to 4 fF (24 fF previously 3 ). For this example, we obtain a response time < 2 ns and a 3dB bandwidth of 230 MHz compared to roughly 30 MHz for the larger device geometry (Figure ).