Characteristics of conductive polymer/silicon heterojunction solar cells with periodic nanostructures

Mono- and multi-crystalline silicon photovoltaics currently still hold more than 80% market share because of the non-toxic, abundant material resources used, and their long-term stabilities. However, the cost of solar power is still more than three times that of fossil fuels, which necessitates a further reduction to accelerate its widespread use. It has been estimated that cell fabrication consumes 30% of the total manufacturing cost due to energy intensive semiconductor processes, such as high temperature furnace for doping, electrodes co-firing, high-vacuum chemical deposition, etc. Therefore, the organic-inorganic hybrid cell concept has been proposed to take advantage of the solution-based processes for rapid and low-cost production and the wide absorption spectrum of silicon. In this work, we demonstrate a hybrid heterojunction solar cell based on the structure of conductive polymer PEDOT:PSS spun cast on n-type crystalline silicon nanorod (SiNR) arrays with periodic arrangements. The nanorod arrays are fabricated by electron beam (E-beam) lithography followed by reactive-ion etching (RIE), which show capability to enhance light harvesting. In addition, SiNRs and PEDOT:PSS can form core-shell structure that provides a large p-n junction area for carrier separation and collection. We measured the optical and photovoltaic characteristics of these devices under a simulated class A solar simulator with a calibrated illumination intensity of 1000 W/m2 for the AM1.5G solar spectrum. A post-RIE damage removal etching (DRE) is subsequently introduced in order to mitigate the surface recombination issues and also alter the surface reflection due to modifications in the nanorod side-wall profile. Finally, we show that the DRE treatment can effectively recover the carrier lifetime and dark current-voltage characteristics of SiNRs hybrid solar cells to resemble the planar counterpart without RIE damages.