A simple two-step surface treatment process is proposed to boost the efficiency of silicon nanowire/PEDOT:PSS hybrid solar cells. The Si nanowires (SiNWs) are first subjected to a low temperature ozone treatment to form a surface sacrificial oxide, followed by a HF etching process to partially remove the oxide. TEM investigation demonstrates that a clean SiNW surface is achieved after the treatment, in contrast to untreated SiNWs that have Ag nanoparticles left on the surface from the metal-catalyzed etching process that is used to form the SiNWs. The cleaner SiNW surface achieved and the thin layer of residual SiO2 on the SiNWs have been found to improve the performance of the hybrid solar cells. Overall, the surface recombination of the hybrid SiNW solar cells is greatly suppressed, resulting in a remarkably improved open circuit voltage of 0.58 V. The power conversion efficiency has also increased from about 10% to 12.4%. The two-step surface treatment method is promising in enhancing the photovoltaic performance of the hybrid silicon solar cells, and can also be applied to other silicon nanostructure based solar cells.

There is a great need for viable alternatives to today’s transparent conductive film using largely indium tin oxide. We report the fabrication of a new type of flexible transparent conductive film using silver nanowires (AgNW) and single-walled carbon nanotube (SWCNT) networks which are fully embedded in a UV curable resin substrate. The hybrid SWCNTs-AgNWs film is relatively flat so that the RMS roughness of the top surface of the film is 3 nm. Addition of SWCNTs networks make the film resistance uniform; without SWCNTs, sheet resistance of the surface composed of just AgNWs in resin varies from 20 Ω/sq to 107 Ω/sq. With addition of SWCNTs embedded in the resin, sheet resistance of the hybrid film is 29 ± 5 Ω/sq and uniform across the 47 mm diameter film discs; further, the optimized film has 85% transparency. Our lamination-transfer UV process doesn’t need solvent for sacrificial substrate removal and leads to good mechanical interlocking of the nano-material networks. Additionally, electrochemical study of the film for supercapacitors application showed an impressive 10 times higher current in cyclic voltammograms compared to the control without SWCNTs. Our fabrication method is simple, cost effective and enables the large-scale fabrication of flat and flexible transparent conductive films.

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We have fabricated and characterized the performance of carrier selective molybdenum oxide (MoO x )/n-Si heterojunction solar cells (HSCs), with the MoO x prepared by both E-beam evaporation (e-MoO x ) and solution process (s-MoO x ) techniques. The s-MoO x /Si HSC demonstrates the best power conversion efficiency of 12.5 %, with an open circuit voltage of 555 mV, short circuit current density of 33.3 mA cm −2 , and fill factor of 67.4% and it is higher than the efficiencies reported to date for s-MoO x /Si HSC. The efficiency achieved is approaching the 13.3% obtained for the e-MoO x /Si HSC. The slightly lower efficiency of s-MoO x /Si HSC is attributed to its carrier extraction loss arising from a higher contact resistivity at the MoO x /n-Si interface. This is also reflected in the selectivity of the contacts, which measures 10.1 for the s-MoO x contact, relative to 11.5 for the e-MoO x contact. Trap-assisted tunneling at the interface is believed to be the main mechanism that influences the cell performance such as open circuit voltage and fill factor, and results in a high ideality factor of ∼3.

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