To fabricate this type of solar cell, a thin layer of PEDOT:PSS was successfully transferred using a simple stamping process onto the top of a SiNW array. As a result of the stamping transfer, conductive channels consisting of nanowire tips interlinked via agglomerated PEDOT:PSS were linearly formed on the top side of the SiNW array as shown above (see image d).

Compared with a bulk-type structure (see image c) consisting of nanowires fully embedded in polymer, the stamped hybrid cell revealed a greater enhancement of the power conversion efficiency (PCE) due to improvements in major photovoltaic parameters such as the short-circuit current, open-circuit voltage, series resistance, shunt resistance, diode ideality factor and optical reflection.

"We are facing some serious limitations for improving the efficiency of bulk hybrid solar cell, such as excessive recombination of free carriers, decay of excitons within an exciton diffusion length and inefficient carrier transport inside the polymer,” said Syed Abdul Moiz, a research professor at Hanyang University. “These limitations can be minimized by incorporating nanowires inside the optimum thickness of polymer close to 70 nm, but unfortunately such a type of hybrid solar cell with nanowire lengths below this optimum thickness becomes much less practical.”

The team is hopeful for the future of the stamped PEDOT:PSS–SiNW hybrid solar cell, and believes that the design could have important implications for device fabrication.

Full details can be found in the journal Nanotechnology.