Fig. 1. Echoes of Dujiangyan in perovskite PDs. (a) Working mechanism of conventional photoconductive-type perovskite PDs (device#1). In this device, the signal electrode collects both dark current and photocurrent, increasing low signal-to-noise ratio. Additionally, the operating voltage accelerates ion migration, causing dark current drift. (b) Working mechanism of new structure perovskite PDs (device#2). In this device, a control electrode separates dark current and photocurrent, boosting the signal-to-noise ratio. Moreover, it ensures uniform potential distribution, curbing ion migration and improving dark current drift. The function of the control electrode bears a striking resemblance to the diversion levees in the Dujiangyan. (c) Dark current curves of device#1 and device#2. (d) Schematic diagram of the Dujiangyan Irrigation System. Ancient Chinese ingeniously managed flood discharge and sediment removal along the Minjiang River by constructing engineering works like diversion levees, sediment-flushing weirs (Feishayan), and bottleneck channels (Baopingkou).