Boosting electrical output of nanostructured silicon hydrovoltaic device via cobalt oxide enabled electrode surface contact

Hydrovoltaic device exploits the omnipresent water evaporation or vapor through functional materials to generate power in a facile and environmentally manner. However, overlooking of the interfacial contact between electrodes and materials is one of the dominant hindering factors in further improving the electrical outputs. Here, we report a high-efficiency silicon nanowire (SiNW) arrays-based hydrovoltaic device featuring a cobalt oxide (CoOx) layer between the top electrode and SiNWs. The CoOx layer functions as a hole-selective layer that reinforces the interfacial charge selectivity and suppresses carrier recombination. Crucially, the unique design of the CoOx-capped SiNWs architecture enables surface contact with the top electrode instead of point contact, which expands the geometric contact area and provides minimal interfacial contact resistance. Benefiting from this facile yet effective contact structure design, the device yields an open-circuit voltage of 0.83 V, a short-circuit current of 160 μA, and a maximum power density of 20 μW·cm-2 (a record among analogous devices). We also showcase that the output power of four series-connected devices viably actuates various colored light-emitting diode (LED) arrays of 25 bulbs. This finding would initiate a promising orientation toward the fabrication of high-performance hydrovoltaic devices.