11%-Efficiency hybrid organic/silicon-nanowire heterojunction solar cell with an intermediate 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane layer

Abstract

Hybrid organic-inorganic heterojunction solar cells based on silicon nanowires (SiNWs) are promising candidates for next-generation photovoltaics owing to potentials for low fabrication cost and high efficiency. The SiNW array, fabricated by a simple metal-assisted wet chemical etching method, produces a large surface-area-to-volume ratio, hence allowing efficient light harvesting and charge collection via the formation of a core-sheath p-n junction. However, previously reported power conversion efficiencies (PCEs) are approximately capped at 10%, which is largely depicted by the interface defect densities that limit the open-circuit voltage (Voc) and fill factor (FF). In this work, we introduce a solution-processed, intermediate 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) layer to mitigate the interface recombination loss for hybrid heterojunction solar cells consisted of SiNWs and conjugate polymer poly(3,4-ethylenedioxy-thiophene): poly(styrenesulfonate) (PEDOT:PSS). A record PCE of 11.0% is achieved in contrast to 9.6% from a reference counterpart without TAPC, which represents an enhancement factor of 14.2% ascribed to noticeable improvement in the Voc and FF. The result is further supported by examining indicators for the interface quality via a suppressed dark saturation current and an enhanced minority carrier lifetime which exhibits an increase from 84 μsec without TAPC to 87 μsec with TAPC.