TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The particles comprise at least 0.5 atomic% of dopant. The dopant is phosphorus or boron. The elemental silicon/germanium nanoparticles have an average primary particle size of no more than 50 nm. The silica etching agent comprises hydrogen fluoride, ammonium hydrogen difluoride and/or ammonium fluoride. The weight ratio of silica/germania nanoparticles to silicon/germanium nanoparticles is 0.01-1. Preferred Method: Simulated printing comprises subjecting the paste to 20 simulated print cycles and then performing the specified viscosity measurements. The depositing of the ink comprises screen printing, inkjet printing or spin coating. The drying of the ink comprises heating to 500-300 degrees C. The method further comprises heating the dried silicon nanoparticle deposit to 700-1200 degrees C to fuse the silicon nanoparticles. The silicon nanoparticles are doped and the method further comprises heating the dried silicon nanoparticle deposit at 700-1200 degrees C to diffuse dopant into the silicon substrate. The initial well mixed dispersion is formed using sonication. The preparation method further comprises sonicating the multiply centrifuged supernatant for 5 minutes to 3.5 hours, where each centrifugation step is performed at 3000-15000 rpm for 5 minutes to 2 hours.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The second solvent comprises N-methylpyrrolidone, ethylene glycol, propylene glycol, glycol ether, terpineol, 2-(2-ethoxyethoxy)ethanol and/or Butyl cellosolve (RTM: 2-Butoxyethanol). The first solvent comprises isopropyl alcohol, acetone, dimethylformamide and/or cyclohexanone. The solvent comprises an alcohol. The alcohol is isopropyl alcohol.    TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The paste further comprises: a cellulose polymer; 0.5-15 wt.% of a hydrophilic polymer, where the paste has 1.5-18 wt.% silicon/germanium nanoparticles; and a dopant liquid. The paste comprises 0-10 wt.% of a first solvent having a boiling point of no more than 165 degrees C, and 65-94.75 wt.% of a second solvent having a boiling point of at least 170 degrees C. The paste has an average viscosity of 5-50 Pa.s at a sheer rate of 2 s-1. The paste has an average post-printing viscosity at a shear of 2 s-1 that is no less than 70%, preferably no less than 90% of an average post-printing viscosity at the 20th print cycle, where a print cycle is simulated with the application of a shear rate of 1000 s-1 to the paste for 60 seconds followed by applying a low shear rate of 2 s-1 to the paste for 200 seconds, and the pre-cycling and post-cycling viscosity are measured at 25 degrees C. EXAMPLE - Doped crystalline silicon particles having an average primary particle size of 20 nm were synthesized. A slurry was formed by adding an appropriate amount of nanoparticle powder to a volume of isopropyl alcohol. The mixture was then initially mixed by bath sonication for 3 hours at ambient temperature to form a dispersion. The dispersion was then centrifuged at 9500 rpm for 20 minutes to remove more poorly dispersed components of the dispersion. The supernatant was then decanted to another centrifuge tube and centrifuged at 9500 rpm for another 20 minutes. The supernatant of the second centrifugation was then decanted and placed in a rotovap for 30 minutes at 137 mbar, to partially remove isopropyl alcohol and concentrate the dispersion to some extent. Subsequently, a volume of propylene glycol was added to the concentrated dispersion and the resulting mixture was subjected to post-centrifugation sonication for 3 hours at ambient temperature. The sonicated mixture was then placed in the rotavapor again to further remove isopropyl alcohol to the maximum amount to give a paste comprised 10-14 wt.% silicon particles, majority of propylene glycol, and some residue of isopropyl alcohol.