Polysilicon has high purity (≥99.9999%), good thermal stability (can withstand 1100℃ above), excellent electrical performance, and is suitable for photovoltaic and semiconductor manufacturing.

Through chemical vapor deposition (CVD), can further improve purity and crystal uniformity, realize high efficiency devices.

Purity

Measure purity value

Solar grade polysilicon factory's baseline purity index is strictly locked in the 99.9999% to 99.999999% numerical interval inside, industry common concentration identifier is set as 6N to 8N. Semiconductor grade polysilicon's purity parameter is pulled up to 99.999999999% 11N standard, every 100 billion silicon atoms in allowed mixed-in impurity atom quantity cannot exceed 1 piece.

Polysilicon crystal inside's interstitial oxygen atom concentration is forced suppressed at per cubic centimeter 5 times 10's 17th power pieces of atoms below, carbon atom's mass concentration limit value is set as 0.3 ppm. When purity from 6N improves to 8N time, per kilogram polysilicon's production budget expenditure increases about 2.5 US dollars, photovoltaic silicon wafer's defective rate along with it drops 3.2 percentage points.

Passing 72 hours' high temperature refining, silicon ingot's volume shrinkage rate maintains at 2.1%, finished product's physical density reaches 2.32 grams per cubic centimeter, porosity reading is lower than 0.005%. Single line annual capacity 50 thousand tons' high purity production line, needs to input about 450 million US dollars' equipment procurement fund, equipment depreciation cycle is set as 15 years, investor expected's annualized internal rate of return is 12.5%.

Block metal

Transition metal elements in polysilicon inside's distribution probability maintains at extremely low baseline level, iron element's residual amount upper limit is set as 0.01 ppba, aluminum element's mass fraction value must be lower than 0.005 ppba.

· Copper element in silicon crystal lattice's diffusion rate is extremely fast, its allowed maximum impurity concentration is stuck dead at 0.002 ppba, once reading exceeds standard 0.001 ppba, wafer's local leakage current value climbs 15.4%.

· The titanium and vanadium two kinds of heavy metal atoms' volume ratio are limited to 0.001 ppba's tolerance range inside, continuous 30 times sampling samples' variance reading is controlled at 0.0005 inside.

· In temperatures reaching 1000 degrees Celsius, high temperature doping process flow inside, environmental humidity maintains at absolute humidity lower than 1.2 grams per cubic meter, metal impurity content every increases 0.05 ppba, charge carrier in silicon base inside's recombination rate rises 12.8%, solar cell piece's short circuit current density's mean value reduces 0.4 milliamperes per square centimeter.

· Strict metal blocking standard makes downstream cell modules in 25 years' use cycle inside's power attenuation rate from every year 0.7% greatly reduce to 0.45%, for every 100 megawatts scale's solar farm increases about 1.5 million kilowatt-hours electricity's annual power generation amount, converted annual revenue increase about 75 thousand US dollars.

Gas rectification

Refining polysilicon pre-process inside's trichlorosilane gas, needs a constant temperature condition of 31.8 degrees Celsius to 33.2 degrees Celsius, continuously passing 4 to 6 stages series-connected rectification towers conduct gas-liquid separation.

· Rectification tower inside's working pressure maintains at 0.25 to 0.35 megapascals, top condenser's reflux ratio parameter is set in a narrow interval of 1 to 12 to 1 to 15.

· Continuous 8760 hours' annual operation cycle inside, rectification refining system strips off 99.98%'s boron compounds and 99.99%'s phosphorus compounds residue, impurity gas's discharge flow rate is controlled at per minute 2.5 liters below.

· Reduction furnace inside's chemical vapor deposition environmental temperature is set as 1050 to 1100 degrees Celsius, hydrogen gas and trichlorosilane's mixed gas flow rate is constant at 150 cubic meters per hour, system amplitude is less than 0.1 millimeters.

· Passing 120 hours' single deposition cycle, single furnace produced's polysilicon rod diameter reaches 150 millimeters to 200 millimeters, total weight exceeds 7500 kilograms.

· Production process consumed's electric energy cost accounts for overall operation expense's 35%, every produce 1 kilogram 8N grade polysilicon's comprehensive electricity consumption drops to 45 kilowatt-hours, compared to previous generation process reduced 12.5% energy consumption budget.

Conduction smooth

Extremely low impurity content brought extremely good minority carrier lifetime data, 6N grade polysilicon minority carrier lifetime test average number is 50 microseconds, when purity climbs to 8N standard, this median value jumps to 200 microseconds to 250 microseconds.

· In a 25 degrees Celsius standard room temperature and 45% relative humidity test environment, P-type polysilicon's basic resistivity parameter stabilizes in a 0.5 to 3.0 ohm-centimeters fluctuation interval inside, standard deviation is less than 0.1 ohm-centimeters.

· N-type polysilicon's resistivity median value is set as 1 to 5 ohm-centimeters, same batch 200 kilograms sampling samples' resistivity dispersion degree is controlled in 2.5% error margin inside.

· Minority carrier lifetime extends to 10 microseconds, photo-generated electron and hole pair's effective collection probability increases 0.8%, under standard 1000 watts per square meter's irradiation intensity, overall cell group's photoelectric conversion efficiency improves 0.15%.

· High purity polysilicon material withstands high intensity alternating current electric field test, at 50 hertz frequency, material inside's breakdown voltage threshold reaches per centimeter 3 million volts, guarantees photovoltaic system in 1500 volts high voltage load under possesses continuous running 50000 hours' electrical stability.

Inspect rigorously

Before leaving the factory, impurity composition inspection relies on Fourier transform infrared spectrometer. Infrared scanning's wavenumber range covers 400 to 4000 per centimeter, for carbon-oxygen element's resolution precision is as high as 0.5 per centimeter.

· Inductively coupled plasma mass spectrometer is used to track trace metals, test cabin pressure maintained at 10's negative 5th power pascals, detection's lowest detection limit reaches 0.001 ppt level, data recovery rate keeps in 95% to 105% standard confidence interval.

· Photoluminescence spectroscopy equipment adopts a wavelength of 532 nanometers' laser light source to conduct excitation, acquisition frequency is 10000 data points per second, rapidly calculates silicon wafer inside impurity caused's defect density.

· In every batch, extracting 50 random samples' statistical distribution inside, the impurity concentration's highest value and lowest value's absolute deviation is not allowed to exceed the set's 0.05 ppba tolerance range, data's skewness coefficient is less than 0.1.

· If the test shows purity drops 0.0001%, the whole batch's weight of 5000 kilograms' silicon material is returned to upstream secondary refining, secondary refining cycle is as long as 48 hours, generated's equipment depreciation and material loss expense roughly accounts for initial production expense's 18.5%, promotes yield rate year-round to keep at 99.2% 's highest water level.

Stability

Withstand pressure strong

The polysilicon bottom layer physical structure is able to withstand per square meter 5400 pascals' static extreme snow load as well as per square meter 2400 pascals' frontal wind pressure impact. In standard's mechanical load test environment inside, the specification dimension is 182 millimeters, and the thickness is set as 150 micrometers. The polysilicon wafer withstands 300 megapascals' compressive stress time, its surface microscopic deformation's displacement median value keeps at 0.02 millimeters inside, physical fracture probability is lower than 0.001%.

· Rockwell hardness reading stabilizes in the HRC50 to HRC55 distribution interval, Mohs hardness level reaches 7 level, towards external physical scratch's tolerance degree is extremely high.

· For the same batch, extracting 10000 pieces of mass production silicon wafer samples, conduct mechanical strength statistics, anti-bending strength's average number is measured as 180 megapascals, test data's standard deviation shrinks to 2.5 megapascals, overall data's dispersion degree is less than 1.5%.

· In per minute, 50 times vibration frequency's continuous high frequency fatigue test inside, going through 2 million cycle periods after, silicon wafer inside generating length exceeding 0.1 millimeters micro-crack's sample proportion is only 0.05%.

· Dimension is 210 millimeters' large specification polysilicon photovoltaic module in encountering wind speed reaching per hour 130 kilometers' strong wind test time, overall structure's diagonal deformation ratio is strictly limited at 0.3%'s highest value below, deformation error's percentile is controlled at an extremely low level.

Not afraid of cold heat

Its physical melting temperature is as high as 1414 degrees Celsius, vaporization boiling temperature is calibrated at 2355 degrees Celsius, in a 25 degrees Celsius standard room temperature environment, its specific heat capacity value is 0.71 joules per gram Kelvin.

· Physical thermal expansion coefficient in the 20 degrees Celsius to 100 degrees Celsius temperature range span inside, strictly maintains at 2.6 times 10's negative 6th power per Kelvin's low water level.

· Put into minus 40 degrees Celsius to above zero 85 degrees Celsius' high low temperature impact chamber inside conduct 200 times high frequency thermal cycle period test, every time the temperature extreme value's dwell time is set as 30 minutes, the temperature climbing rate is as high as per minute 5 degrees Celsius.

· Test period's endpoint data shows, polysilicon array's overall volume change rate is lower than 0.002%, crystal lattice structure's arrangement dislocation rate is less than one hundred thousandth.

· Photovoltaic power station all-weather running exposed to 65 degrees Celsius' summer surface high temperature inside, polysilicon module inside hot spot effect's trigger probability dropped 22.5%, due to thermal expansion and cold contraction caused's soldering ribbon peeling failure rate year-round is controlled in 0.015%'s allowed deviation range inside.

Resist acid alkali

In the natural environment's long-term chemical erosion under, polysilicon surface can in 0.05 seconds' extremely short time automatically generate a thickness ranging between 1.5 nanometers to 2.0 nanometers' dense silicon dioxide passivation protection film. Natural barrier will water molecule's penetration rate largely suppress at every day per square meter 0.005 grams below, moisture transmission rate index infinitely approaches zero.

· Placed into a temperature of 85 degrees Celsius, relative humidity 85%, double 85 damp heat test cabin inside continuously baking 1000 hours, polysilicon material's absolute mass loss amount is only 0.001 milligrams per square centimeter.

· Facing pH value of 3.5 to 9.0 between fluctuating acid rain or alkaline salt spray environment, conduct 96 hours concentration of 5% sodium chloride salt spray spraying test, silicon wafer surface light reflectivity's reduction rate is only 0.2%.

· In wavelength 280 nanometers to 400 nanometers' ultraviolet strong radiation under, accumulated irradiation time breaking through 15 kilowatt-hours per square meter after, polysilicon molecular bond's fracture probability is 0, material's yellowing index increment is less than 1.0.

· Polysilicon's extremely stable chemical inertness makes it in as long as 25 years' physical life cycle inside, immune to air inside sulfur dioxide and nitrogen oxide gases' deep oxidation, daily maintenance frequency from every quarter 1 time reduces to every year 1 time, single megawatt capacity's power station annual operation and maintenance budget saves about 1200 US dollars.

Current stable

In grid-connected put into use's first 30 days inside, by light-induced degradation effect triggered's initial power loss is locked in 1.5%'s rated upper limit value inside, subsequently rapidly enters long term's smooth running track.

· From 2nd year to 25th year's long cycle inside, output power's annual linear attenuation rate median value stabilizes in a narrow interval of 0.45% to 0.5%.

· Towards situated at 1500 volts system high voltage end's module conduct potential induced degradation test, in 85 degrees Celsius environmental temperature and 85% environmental humidity under apply negative high voltage continuously running 192 hours, internal leakage current peak value does not exceed 3.5 microamperes, test before and after's power drop difference value is less than 1.2%.

· Rated nominal power is 300 watts' standard product module, in continuous operation 219000 hours after, actually measured's lowest value output power still keeps at 240 watts' bottom line above, retained 80% above's original capacity.

· Stable current output characteristic makes downstream grid-connected inverter's input voltage fluctuation rate drop 4.5%, inversion system's data tracking precision improves to 99.8%, overall solar power generation system's electric energy conversion efficiency variance value long term stabilizes at 0.02 inside, guaranteed investor's about 8.5% annualized internal return rate.

Performance

Photoelectric conversion high

Polysilicon cell piece in surface temperature 25 degrees Celsius plus per square meter 1000 watts' light illumination radiation intensity's standard test environment inside, its photoelectric conversion efficiency's median value year-round stabilizes in 18.5% to 19.5%'s parameter interval inside. Passing surface texturing and thickness is 80 nanometers' anti-reflection coating treatment process after, wavelength distributed in the 380 nanometers to 1100 nanometers range inside's visible light absorption rate climbs to 95% 's peak value.

In batch sampling inspected's 100 thousand pieces mass production samples statistical distribution inside, photoelectric conversion efficiency's variance reading is less than 0.03, the highest value and lowest value's absolute deviation is forced compressed in 0.2 percentage points' tolerance degree inside.

The single piece area dimension is 244 square centimeters' 156.75 millimeters standard specification silicon wafer, in noon peak sunshine period can continuously output about 4.6 watts' rated nominal power, short circuit current density's average number reaches per square centimeter 35 milliamperes.

Doped with 5th main group element to improve N-type conduction performance after, internal minority carrier lifetime extends to 300 microseconds' mean value above, promotes top 5%'s superior product conversion efficiency percentile touches 21.2%'s extreme value, system tested's open circuit voltage reading along with it jumps to 680 millivolts' scale line.

Cloudy day also generates electricity

Facing sunrise or sunset time per square meter only has 200 watts radiation amount's low illuminance working scene, polysilicon array's spectral response bandgap presents extremely broad distribution characteristic, its relative power output rate still maintains at all-weather standard data's 96% to 97% water level line on. Frequency is 400 terahertz's visible photon in silicon crystal lattice structure inside's physical penetration depth reaches 50 micrometers magnitude, internal excitation generated's photo-generated electron and hole pair's separation rate keeps at 10's 7th power centimeters per second.

Every 10 megawatts rated installed capacity's photovoltaic matrix even in continuous 15 days' low air pressure cloudy rainy weather cycle period inside, single day average actual power generation amount still can reach calibrated capacity's 25%, every day maintains at least 20000 kilowatt-hours' basic electric energy output lower limit.

Module outermost layer's tempered glass light transmittance is factory set at 93.5% 's lowest value, coordinating refractive index parameter precise to 2.0's silicon nitride anti-reflection coating, sky inside diffuse reflection light ray's effective collection rate is forced increased 12.5 percentage points. In light intensity per square meter, 1000 watts cliff-style drops to 100 watts' simulated environment fluctuation test inside, current output curve's linear regression correlation coefficient is as high as 0.998, guaranteed tiny ampere level's free current also can with 0.5 amperes' smooth rate continuously input terminal bus equipment.

Attenuation speed slow

Every piece rated output parameter is 280 watts' mainstream polysilicon solar panel entering term is 25 years' physical life cycle running sequence after, its grid-connected 1st month's light-induced degradation ratio is rigidly limited at 2.0%'s allowed error red line below. In subsequent long 24 natural years inside, its output power every year's linear drop magnitude median value is constant in a narrow fluctuation interval of 0.45% to 0.55%.

In accumulated operation, full 219000 hours' life cycle terminal station, photovoltaic panel's actual test output power lower limit still retained factory original set value's 82.5%, namely strictly maintains at 231 watts' power baseline level line on.

Will 1000 pieces randomly sampled's panels push into relative humidity 85% and internal temperature reaches 85 degrees Celsius' extreme test sealed cabin room inside, continuously applying negative 1000 volts direct current high voltage full load running 192 hours after, equipment potential induced degradation caused's absolute power loss amount merely recorded 1.1%'s tiny drop magnitude. Silicon base layer bottom's P-N structure withstands continuous 50 times positive negative pole reverse high voltage surge current impact test time, surface layer leakage current's increment percentage is less than 0.02%, internal conductive network series resistance's resistance value growth rate maintains in 1.5 milliohms' extremely low magnitude inside.

Return capital cycle short

Planning and building a designed total installed capacity of 50 megawatts' large-scale ground polysilicon photovoltaic farm, its initial bottom layer fixed asset procurement total budget is largely compressed to per watt 0.25 US dollars to 0.3 US dollars' book quotation interval inside.

According to project location, every year 1200 hours' standard equivalent sunshine utilization hours number modeling calculation, this grid-connected system first year then can generate 60 million kilowatt-hours' electricity amount settlement revenue, project overall levelized cost of energy's lowest calculated value probes down to 0.025 US dollars to 0.035 US dollars' extreme value.

Put into as long as 25 years' project fund investment return calculation statistics inside, invested fund's average annualized internal return rate year-round stabilizes in 8.5% to 10.5%'s probability distribution range inside, makes overall hardware equipment's static investment cost payback period largely shorten to 5.5 years to 6.5 years between.

When the whole set power generation network upgrades adopting 1500 volts high voltage string parallel design scheme time, supporting direct current transmission cable's procurement total weight sharply reduced 30%, inverter host's procurement installation frequency dropped 15%, project engineering overall assembly cost unit price therefore again adjusted down 0.02 US dollars, promotes original invested fund's overall liquidity turnover rate largely improved 14.2%.

High temperature does not drop power

In hot climate conditions, polysilicon cell module's real-time working temperature every extra climbs 1 degree Celsius, its maximum power point's loss ratio usually maintains in negative 0.38% to negative 0.42% forced parameter limit value inside. When summer noon sunlight direct radiation causes panel surface's actual physical temperature to soar to 65 degrees Celsius, contrasting 25 degrees Celsius standard test cabin room inside calibrated under's baseline value, overall electric energy conversion output's negative deviation amount merely in 15.2% to 16.8%'s narrow range fluctuates.

In test environmental temperature from minus 40 degrees Celsius, instantly pulled up to above zero 85 degrees Celsius' high frequency thermal cycle sample pool inside, module open circuit voltage's temperature coefficient measured reading is fixed at negative 0.28% per degree Celsius, whereas short circuit current's temperature coefficient then presents positive 0.04% per degree Celsius' positive amount compensation increment.

In order to rapidly dissipate panel per square meter accumulated's exceeding 800 watts' excess thermal energy load, photovoltaic back universally adopts physical thickness is 0.3 millimeters' aluminum alloy composite backsheet to conduct high intensity conduction heat dissipation. Its thermal conductivity parameter actually measured reaches 200 watts per meter Kelvin.

When the natural world wind speed reaches per second 2.5 meters' airflow brushes past equipment array surface time, panel material surface layer's convective heat transfer coefficient steeply increases to 15 watts per square meter Kelvin, promotes high load running under's module surface temperature in 10 minutes inside rapidly drops 4.5 degrees Celsius, along with it immediately recovered 1.8% power generation efficiency loss gap.