Electroforming of Si NCs/p-Si photovoltaic devices: Enhancement of the conversion efficiency through resistive switching

In this work, the relation between the photovoltaic and resistive switching (RS) properties of metal-oxide-semiconductor devices containing Si nanocrystal (Si NC) superlattices is investigated. A first approximation concludes that the low resistance state achieved by the RS process allows for enhanced photogenerated carrier extraction when compared to the high resistance state and pristine devices. By using different current compliance values during the electroforming process, the low resistance state is further modified, improving its conductivity and the collection probability of photogenerated carriers. Conversion efficiency is enhanced by at least one and up to five orders of magnitude by applying different electroforming processes. In addition to promoting the RS properties in these devices, spectral response measurements demonstrate that Si NCs are partially responsible for the optical absorption, and that their contribution is maintained after electroforming. We thus conclude that the proposed methodology can improve the conversion efficiency of this and other multijunction solar cells or structures that also exhibit RS properties. Through RS, a dense network of conductive filaments is promoted in the insulating region, which reduces the travel distance of photocarriers for their collection.
This work was financially supported by the Spanish Ministry of Economy, Industry and Competitiveness (TEC2016-76849-C2-1-R) and the German Research Foundation (ZA191/27-3 and ZA191/33-1). J.L.F. acknowledges financial support from the subprogram “Ayudas para la Formación de Profesorado Universitario” (FPU16/06257) from the Spanish Ministry of Education, Culture and Sports.