Emitter structure based on silicon components to be used in a photovoltaic converter and a method for production of the photovoltaic device

Emitter structure made of silicon nano components to be used in a photovoltaic converter able to convert high energy photons into free electrons in particular UV and visible photons as well as IR photons, this improved emitter structure being part of a slab, wafer or chip of p-type or n-type photovoltaic material, having a top surface intended to be exposed to photonic radiation mainly to sun radiation, having a built-in PN junction delimiting an emitter part and a base part, having front and rear electrodes and comprising at least one area or region specifically designed or adapted to absorb high energy or energetic photons and located adjacent or near one hetero-interface, said slab, wafer or chip of photovoltaic material comprises also at least one nanometamaterial MTM region forming a low-energy secondary carrier generation cavity, which is contiguous or proximate to the at least one absorption area or region for the energetic photons and subjected to a built-in or applied electrical field having an intensity sufficient to withdraw and move away the secondary electrons liberated by the primary hot electrons from their initial sites within the concerned nanometamaterial MTM region, at a speed sufficient to prevent their return into said nanometamaterial MTM region, thus forming a substructure performing multi-stage conversion, wherein the density of divacancies within the nanometamematerial MTM region(s) is greater than 1018 diva-cancies/cm3, preferably greater than 1019 divacancies/cm3, most preferably greater than 1020 diva-cancies/cm3 and the conduction between the nanometamaterial MTM and the respectively adjacent n-type material has a time constant which is at the most of the same magnitude that the secondary carrier generation time constant, in which a carrier collection limit CCL separates the emitter in two parts:

• the upper emitter which is an electronically dead zone and the lower emitter which is electronically active, this carrier collection limit CCL being defined as the interface with its potential barrier blocking generated carriers to move towards the PN collection junction, characterized in that the amorphous semiconductor material layer is conformed by a process of insertion, deposition or implantation of ions or electrons or any equivalent process into a relief made of a succession of concavities or protrusions or platforms separated by interruptions or discontinuities in one or several continuous or discontinuous layer(s) and in that the upper surfaces of these reliefs of amorphous semi-conductor consist in a nanometamaterial MTM.

A method for producing a photovoltaic material able to absorb and exploit high energy or energetic photons, in particular UV and visible photons, in which the method comprises the steps of:

• a) providing or producing a conventional p-type or n-type photovoltaic material made of inorganic crystalline semiconductor material(s), such as Si or GaS, having a top surface intended to be exposed to photonic radiation, having a built-in PN junction delimiting an emitter part and a base part and comprising at least one area or region specifically designed, treated or adapted to absorb high energy or energetic photons, located adjacent or near at least one hetero-interface;
• b) generating or maintaining structural defects within an n-type area of said emitter and/or base part of the material consisting of divacancies able to function as low-energy secondary generation centers grouped to-gether in (a) nanometric formation(s) and persistent under production process and photovoltaic conversion conditions;
• c) introducing, in particular diffusing or implanting, n-type doping impurities, such as phosphorus or arsenic, according to determined intensity, energy and profile in order to put the divacancies into an electrical charge state in which they are saturated with weakly bonded electrons and to provide an excellent conduction within said or each region of implanted impurities, such as metallic type conduction in heavily doped semiconductor material;
• wherein steps b) an c) are performed in such a way that they result in at least one semiconductor based metamaterial field or region being created, as a transitional region of the or a hetero-interface;
• d) providing a built-in electric field or means to apply an electric field which encompasses or extends over said or each metamaterial field or region and shows an intensity sufficient to withdraw and move away said liberated secondary electrons from their initial sites within the concerned metamaterial area or region, at a speed sufficient to prevent their return into said meta-material region or field;
• e) providing a succession of protrusions or platforms at the amorphous semiconductor material level conformed by a process of insertion, deposition or implantation of ions or electrons or any equivalent process into a relief made of a succession of protrusions separated by hollows or interruptions or discontinuities in the shape of one or several continuous or discontinuous layer(s),
• wherein said method also comprises, preferably after step c), and/or after e) at least one thermal treatment step of the material of determined duration and intensity, with a total energy balance of the thermal treatment for one continuous nanoscale planar metamaterial layer buried within the emitter part of the photovoltaic material which is approximately equivalent to that of a continuous thermal annealing of a duration of about 30 to 50 minutes, preferably of about 40 minutes, at a temperature comprised between 450° C. and 600° C., preferably of about 500° C.,
• wherein the at least metamaterial field or region is created, as a result of above steps b) and c), in an area located continuous or proximate to the or an absorption area or region for the energetic photons of the photonic radiation impacting said photovoltaic material, at least within the range of thermalization of the primary electrons liberated directly by said energetic photons and which collide with metamaterial low-energy generation centers liberating secondary generation electrons in a multistage processing, the order of which depends on remaining energy kept by the primary electrons at the moment of their generation collision,
• wherein the setting of the parameters of the successive operational production steps are such that the thickness of the or each planar amorphous semiconductor material layer is comprised between 10 nm and 50 nm and that the width of the respectively associated material field(s) or region(s), in the shape of (a) continuous or discontinous layer(s), is less than 10 nm, the semiconductor material having preferably a thickness comprised within 5 μm and 500 μm, preferably between 10 μm and 280 μm, and,
• wherein steps b) and c) are further performed in such a way that, on the one hand, the density of divacancies within the metamaterial field(s) or region(s) is greater than 1018 divacancies/cm3, preferably greater than 1019 divacancies/cm3, most preferably greater than 1020 divacancies/cm3 and, on the other hand, the conduction between the metamaterial and the respectively adjacent N-type material has a time constant which is at the most of the same magnitude than the secondary carrier generation time constant in order to create a relief which consists of a succession of concavities or protrusions and hollows or interruptions or discontinuities in or with the amorphized silicon layer a-Si in which these forms are separated from the silicon crystalline mass c-Si by a nanometamaterial MTM which is a metamaterial derived from crystalline silicone c-Si.