RU2502156C1 - Comb type silicon photoelectric converter and method for production thereof - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to silicon multistage photoelectric converters of solar cells. The invention discloses a comb type design of a photoelectric converter, which enables to form in diode cells thereof the largest possible volume of the space-charge region of p-n junctions where collection of minority charge carriers occurs most efficiently. The invention discloses a design and a method of making said comb type silicon monocrystalline multistage photoelectric converter.

EFFECT: invention increases efficiency of photoelectric converters.

2 cl, 7 dwg

Description

The present invention relates to the field of photovoltaic cells (PECs) for solar cells.

The "traditional" single-junction (OP) PEC design is known with a perpendicular to the direction of the light radiation flux of the light receiving surface p ⁺ -n ^- -n ⁺ (p ⁺ -p ^- -n ⁺ ) junction - a horizontal diode cell (ДЯ), on the surface of which a light-brightening coating is located (Fig. 1a, b). Such solar cells have a low efficiency (efficiency), about 14%, and do not allow to obtain a high value of the output voltage of more than 0.6 V, which limits the scope of their application in solar panels with radiation concentrators [1. Zee. C. Physics of Semiconductor Devices, 1972].

A known design (Fig. 2) of a multi-junction (MF) silicon single-crystal PEC, containing diode cells (DJ) with a light-brightening coating placed on their light-receiving surface and with single p ⁺ -n ^- -n ⁺ (p ⁺ -p ^- -) located in them n ⁺ ) transitions in the direction perpendicular to the light-receiving surface, connected to a single structure by metal anode and cathode electrodes [2. Tyukhov I.I. and others. "A method of manufacturing a semiconductor photoconverter", RF Patent No. 2147472, published 1999.03.10 .; 3. E.G. Hook et al. Characteristics of a silicon multi transition solar cell with vertical pn junctions. Fr. Physics and technology of semiconductors. 1997 G. 31, No. 7 p. 855-858].

Such PECs have a low efficiency, (less than 12%), since they have a relatively small volume of the space charge region (SCR) of the pn junction adjacent to the photosensitive surface of the PEC.

Known for the prototype (Fig. 3), the MP design of a silicon single-crystal PEC, containing diode cells with a light-receiving surface perpendicular to the horizontal (perpendicular to the direction of light), single vertical n ⁺ -p ^- -p ⁺ (p ⁺ - n ^- -n ⁺⁾ junctions and solar cells arranged in parallel to the light-receiving surface of the horizontal n ⁺ -p ^- (p ⁺ -n ^-) transitions, all transitions are unified metal cathode and anode electrodes of corresponding continuously on the surface regions - n ⁺ (p ⁺⁾ type perpendicular single n ⁺ p ^- p ⁺ (p ⁺ -n ^- -n ⁺⁾ junctions [4. Murashev V.N. et al. “Semiconductor photoconverter and method for its manufacture”, RF Patent No. 2377695 dated 12/27/2009].

A method for its manufacture, including

- the formation of vertical single p ⁺ -n ^- -n ⁺ (p ⁺ -p ^- -n ⁺ ) transitions on the surface of single-crystal silicon wafers, metallization of the wafer surface, assembly of wafers into a column with gaskets made of aluminum foil, alloying in a vacuum furnace, cutting a column on the structure, the formation of horizontal p ⁺ -n ⁺ junctions, the connection of current-carrying contacts and the application of a dielectric light-brightening coating.

The disadvantages of the prototype design are also the impossibility of achieving the largest SCR of pn junctions and, accordingly, the efficiency of the photoconverter, as well as the technological problem of the formation of several pn junction perpendicular to the radiation by ion doping with high ion energy (more than 800 keV).

The aim of the invention is to increase the efficiency of the photoconverter and simplify the technology of its manufacture.

The first goal is achieved by creating a “comb-like” FP design with a maximum space charge region (SCR) created by pn junctions, which largely determine the collection efficiency of charge carriers generated by solar radiation.

The "comb" design of a silicon single-crystal PEC contains additional vertical n in diode cells^--r (p^--n) transitions, and their regions n (p) type connected respectively by areas - n⁺(R⁺) of type n⁺-R^- (R⁺-n^-) horizontal transitions to regions - n⁺(R⁺) type of vertical single p⁺-n^--n⁺(R⁺-R^--n⁺) transitions.

The second goal is to simplify the fabrication of PECs by the fact that before the formation of single vertical p ⁺ -n ^- -n ⁺ (p ⁺ -p ^- -n ⁺ ) single transitions on the surface of single-crystal silicon wafers, lightly doped additional vertical n ^- -p (p ^- -n) transitions, then vertical single transitions are formed, then after cutting the plates, horizontal n ^- -p (p ^- -n) are formed, and the impurity concentration in the additional p ^- -n junctions is more than an order of magnitude less than the concentration of impurities and in horizontal n ⁺ -p ^- (p ⁺ -n ^- ) transitions, in which, in turn, the impurity concentration is an order of magnitude lower than the impurity concentration in regions - n ⁺ (p ⁺ ) of the type of vertical single transitions.

The design of the “comb” photomultiplier is illustrated by the figures (Fig. 4 and Fig. 5), which show the possible variants of the photoconductor structure with 2 and 4 additional vertical pn junctions, respectively.

Fig. 4a, b, c respectively shows the structure (section), a top and bottom view, the photomultiplier which according to the invention contains diode cells (ДА) - 1, with a light-brightening coating applied on them - 2, connected to a single structure by metal cathode - 3 and anode - 4 electrodes, with semiconductor regions located respectively on their surface - 5 n ⁺ (p ⁺ ) type and - 6 p ⁺ (n ⁺ ) type single vertical n ⁺ -p ^- -p ⁺ (p ⁺ -n ^- -n ⁺ ) transitions. On the upper and lower surfaces of ДЯ - 1, respectively, there are semiconductor regions - 7 n ⁺ (p ⁺ ) type - 8 p ⁺ (n ⁺ ) type, horizontal n ⁺ -p ^- (p ⁺ -n ^- ) junctions. On the surface of the regions - 5 n ⁺ (p ⁺ ) type and - 6 p ⁺ (n ⁺ ) type, respectively, are located regions of -9 p ^- (n ^- ) type and - 10 n ^- (p ^- ) type forming with them, respectively, single n ⁺ -p ^- (p ⁺ -n ^- ) and additional p ⁺ -n ^- (n ⁺ -p ^- ) transitions.

The photomultiplier in Fig. 5 contains solar AJ - 1, which contains several (4) additional vertical p ⁺ -n ^- (n ⁺ -p ^- ) transitions formed by additional regions - 11 p ^- (n ^- ) type and - 12 n ^- (p ^- ) type with areas - 6 p ⁺ (n ⁺ ) type and - 10 n ^- (p ^- ) type, respectively.

Manufacturing technology.

FEP, according to the invention, can be manufactured by a relatively simple technology (without the use of a photolithographic process, which reduces the cost of its manufacture). For example, according to the technology shown in Fig.6a-e:

a) - in plates of p ^- type KDB 10 Ohm · cm, ion doping of phosphorus with a dose of 2-4 μCul is carried out, followed by distillation of the impurity for 4 hours at a temperature of 950 ° C;

b) - then form the diffusion of boron and phosphorus p ⁺ - and n ⁺ -regions;

c) - sinter (alloy, spliced) plates through gaskets of metal foil in the foot;

g) - cut a stack of plates on individual photoconverters;

d) - phosphorus and boron are implanted in the lower and upper surfaces of the FP with a dose of 50 and 40 μCul, respectively, and photon annealing of radiation defects is carried out;

- apply silicon oxide (SiO ₂ ) and an antireflection coating (Si ₃ N ₄ ).

A similar technology is used to realize the construction of phase transitions with 4 parallel transitions; for this, in step b) three p-n junctions are formed by sequential ion implantation (it is also possible to perform p-n junctions using the epitaxial build-up operation).

Electric equivalent circuit of solar cells.

Conventional phase transition (Fig. 7, a) differs significantly from the proposed photomultiplier (Fig. 7, b) by the presence of pn junctions in series and in parallel, which also provides greater stability of the battery at different radiation intensities.

Marked here

-D ₁ - single vertical n-p-transitions;

- D ₂ - horizontal n-p-transitions;

- D ₃ , D ₄ - additional vertical n-p-transitions.

Technical advantages of the invention.

As can be seen from Fig. 4 and Fig. 5, the n- and p-regions of the photoconverter form a comb design, which makes it possible to realize the maximum volume of the space charge region, in which charge carriers generated by light are collected most efficiently, as compared to the quasineutral region, surface and in the volume of the semiconductor material of solar cells. In this case, the best option for the efficiency of the photomultiplier is achieved when the distance between the boundaries of the pn junctions of the structure is equal to the total value of the thickness of the space charge regions formed by the contact potential difference of the pn junctions.

Theoretical estimates show the possibility of achieving an efficiency of up to 32% in converters of this type.

Despite a slightly higher cost, compared to traditional planar batteries, multi-junction photomultipliers are quite competitive and promising, given their high heat resistance and their ability to work with radiation concentrators.

Claims (2)

1. The design of the comb silicon single-crystal multi-junction photoelectric Converter, containing diode cells with perpendicular horizontal light-receiving surface, vertical single n ⁺ -p ^- -p ⁺ (p ⁺ -n ^- -n ⁺ ) junctions and located in the diode cells, in parallel to the light-receiving surface, horizontal n ⁺ -p ^- (p ⁺ -n ^- ) junctions, and all the junctions are connected into a single structure by metal cathode and anode electrodes located respectively on the region features - n ⁺ (p +) type of perpendicular single n ⁺ -p ^- -p ⁺ (p ⁺ -n ^- -n ⁺ ) junctions, characterized in that it contains additional vertical n ^- -p (p ^- - in diode cells n) transitions, and their regions of n (p) type are connected respectively by regions - n ⁺ (p ⁺ ) of type n ⁺ -p ^- (p ⁺ -n ^- ) of horizontal transitions to regions - n ⁺ (p ⁺ ) of type vertical single p ⁺ -n ^- -n ⁺ (p ⁺ -p ^- -n ⁺ ) transitions. 2. A method of manufacturing a design of a comb silicon single-crystal multi-junction photovoltaic converter, comprising forming vertical single p ⁺ -n ^- -n ⁺ (p ⁺ -p ^- -n ⁺ ) junctions on the surface of single-crystal silicon wafers, metallization of the wafer surface, assembly of wafers in a column with spacers of aluminum foil in a vacuum fusion furnace, cutting the column to the structure, the formation of horizontal p ⁺ -n ⁺ junctions joining tokovyvodyaschih contacts and deposition of a dielectric vetoprosvetlyayuschego coating, characterized in that prior to the formation on the surface of the wafer of monocrystalline silicon single vertical p ⁺ -n ^- -n ⁺ (p ⁺ -p ^- -n ⁺⁾ single transitions in the screen plates are formed by additional vertical weakly doped n ^- p ( p ^- n) transitions, then vertical single transitions are formed, then after cutting the plates, horizontal n ^- p (p ^- n) are formed, while the impurity concentration in the additional p ^- n junctions is more than an order of magnitude lower than the impurity concentration in horizontal n ⁺ -p ^- (p ⁺ -n ^- ) transitions, in which, in turn, the impurity concentration in is an order of magnitude lower than the impurity concentration in regions - n ⁺ (p ⁺ ) of the type of vertical single transitions.

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