A Capacitor-type Faradaic Junction for Direct Solar Energy Conversion and Storage.

Two-electrode solar rechargeable devices trigger intense attention due to their potential applications in solar energy conversion and storage. However, interface energy barriers lead to severe loss of output voltage and negligible dark discharge current. Therefore, external biases are required for dark discharge in these devices, limiting their practical applications. Herein, we report a new two-electrode device of Si/WO3 /H2SO4(aq) /C that can work without bias. To the best of our knowledge, the device indicates the highest dark output power among all of the two-electrode solar rechargeable devices. The device based on a Si/WO3 junction indicates photo-induced adjustable interface barrier height during charge transfer, which can overcome the energy barrier and realize dark discharge without bias. Due to the novel interface characteristic, the Si/WO3 is designated as a capacitor-type Faradaic junction for the first time. The concept of a capacitor-type Faradaic junction paves an avenue to construct other new devices in solar cells, artificial synapses , smart windows and so on.