Obviousness

The provided patent text, including its "Prior Art keywords" and "Prior art date," does not contain a list of specific prior art references (e.g., patent numbers, publications) that can be combined to perform a detailed obviousness analysis under 35 U.S.C. § 103 for US Patent 9,130,074. The "Prior art keywords" (silicon, layer, conductive, type, doped) and the "Prior art date" (April 21, 2009) indicate the general technical field and the relevant timeframe for prior art but do not provide specific documents or disclosures.

While the "Background of the Invention" and "Description of the Invention" sections of the patent describe certain elements as generally known in the art, these are presented as common knowledge or existing challenges rather than specific, citable prior art documents. For instance, the patent acknowledges the general knowledge of:

• The use of silicon wafers as central substrates for solar cells.
• Various materials for electrically passivating interface layers, such as thermally grown silicon oxide, PECVD deposited silicon nitride, intrinsic amorphous silicon, aluminum oxide, aluminum nitride, phosphorus nitride, and titanium nitride.
• Methods for reducing carrier recombination and forming high-low or p-n junctions through the diffusion of doping atoms.
• The concept of heterojunction cells using intrinsic amorphous silicon followed by doped amorphous silicon layers.
• General deposition methods like PECVD, APCVD, LPCVD, PVD, and plating.
• The capability of thermal treatment to convert amorphous silicon layers into polycrystalline silicon layers.
• Standard metallization techniques for electrodes.

However, the independent Claim 1 of US 9,130,074 describes a method that integrates specific thermal treatment steps (at least 500°C) to simultaneously achieve multiple outcomes: crystallization of an amorphous silicon-containing compound into a polycrystalline film, enhancement of the film's optical transmissivity, activation of doping atoms, and diffusion of dopant atoms into the silicon wafer to form a p-n junction or high-low junction. The patent explicitly presents these combined functions of the thermal treatment on an amorphous, silicon-containing compound as novel aspects of the "present invention" in its summary and detailed description.

Without specific prior art references that individually or collectively disclose these precise combinations of layers, materials, and, critically, the multifunctional thermal treatment presented as an aspect of the invention, it is not possible to identify combinations of prior art references from the provided text that would render Claim 1 obvious. The patent itself does not disclose a prior art combination that achieves all the recited elements, particularly the integrated functions of the thermal treatment step as claimed.