CN102254966A

CN102254966A - CdZnTe (cadmium zinc telluride) thin film solar cell with gradient band gap structure

Info

Publication number: CN102254966A
Application number: CN2011101738620A
Authority: CN
Inventors: 曹鸿; 江锦春; 胡古今; 王善力; 褚君浩
Original assignee: SHANGHAI SOLAR BATTERY RESEARCH AND DEVELOPMENT CENTER
Current assignee: SHANGHAI SOLAR BATTERY RESEARCH AND DEVELOPMENT CENTER
Priority date: 2011-06-23
Filing date: 2011-06-23
Publication date: 2011-11-23

Abstract

The invention discloses a CdZnTe (cadmium zinc telluride) thin film solar cell with a gradient band gap structure, comprising a glass substrate, wherein a front electrode layer of transparent conducting oxides, an n-type CdS (cadmium sulfide) window layer, a p-type Cd1-xZnxTe absorption layer and a back electrode layer are deposited on the glass substrate in sequence; the p-type Cd1-xZnxTe absorption layer comprises three areas; the band gap in an intermediate area is not changed and mainly used for strengthening the absorption of sun peak spectrums; and the two areas at two sides are of a gradient band gap structure and used for broadening the absorption range of the solar spectrums. The structure is used to reduce the back surface recombination rate of a cell carrier, improve the ohmic contact of a back electrode of the cell and increase the open-circuit voltage and the short-circuit current of the cell, thus improving the performances of the cell.

Description

Tellurium zincium vestalium thin-film solar cell with graded bandgap structure

Technical field

The present invention relates to thin-film solar cells, be meant a kind of tellurium zinc cadmium (Cd especially with graded bandgap structure _1-xZn _xTe) thin-film solar cells.

Background technology

Solar cell is the device that luminous energy is directly changed into electric energy, if seek out high conversion efficiency, should take into full account the coupling of battery light absorption and solar spectrum, and the energy gap of absorbing material is best about 1.45eV under the general condition.The energy gap of CdTe is 1.45eV, and is direct transition section bar material, and absorption coefficient sharply increases near energy gap, and thickness is the film of 1um, is enough to absorb more than 99% of emittance greater than CdTe forbidden band energy, thus CdTe can do very thin.Yet,, become the key technical problem that this class battery of development is badly in need of solution owing to be difficult to form good Ohmic contact between P type CdTe and the back electrode.

1993, people such as Doty grew high-quality Cd for the first time _1-xZn _xThe Te crystal.Because of Cd _1-xZn _xThe energy gap of Te crystal can change with component x, good mechanical strength, high resistivity, good light sensitive characteristic and charge transmission etc. are used widely.Portion C d with in the Zn replacement zincblende lattce structure CdTe lattice forms ternary compound Cd _1-xZn _xTe, the crystal structure of not appreciable impact of the adding material of Zn.Cd _1-xZn _xTe can be counted as the solid solution of two kinds of binary compound ZnTe and CdTe, changes Cd _1-xZn _xThe content of Zn among the Te, i.e. x value, some important physical propertys can change in the scope of anticipation.Lattice constant as it sexually revises in 0.61004～0.64829nm top-stitching with the x value; Its energy gap with the x value at 1.45eV to adjustable continuously between 2.26eV.If at deposition ternary alloy three-partalloy Cd _1-xZn _xIn the Te process, rationally control of the variation of x value, the Cd that preparation has graded bandgap structure with film thickness _1-xZn _xThe Te polycrystal film and with it as light absorbing material, just might produce the solar cell of high electricity conversion.

The Cd that Chinese patent CN 101276854A proposes _1-xZn _xThe Te film is a graded bandgap structure, this band gap structure triangular in shape, though this graded bandgap structure can be used for widening the response wave band of solar cell, solve ohmic contact problem with dorsum electrode layer, but owing to the best energy gap near the solar radiation spectrum peak is 1.45eV, the energy gap of this triangular structure can not fully absorb the sunlight in the solar radiation spectrum peak scope, thereby can reduce the short circuit current of battery.

Summary of the invention

The objective of the invention is to propose a kind of graded bandgap structure that has, can fully absorb the Cd of sun peak value spectrum _1-xZn _xThe Te thin-film solar cells.

Thin-film solar cells with graded bandgap structure of the present invention comprises: glass substrate deposits electrode layer before the transparent conductive oxide, n type CdS Window layer, p type Cd successively on glass substrate _1-xZn _xTe absorbed layer, dorsum electrode layer.

Said p type Cd _1-xZn _xThe Te absorbed layer is a first area Cd who deposits successively on n type CdS Window layer _1-xZn _xTe absorbed layer, second area Cd _1-xZn _xTe absorbed layer and the 3rd zone C d _1-xZn _xThe Te absorbed layer.

Said first area Cd _1-xZn _xThe Te absorbed layer is a graded bandgap structure, and by 1 linear gradient to 0, the thickness of this absorbed layer is the 500-1800 nanometer to its component x value from the CdS Window layer along thickness direction.The Cd that this is regional _1-xZn _xThe energy gap of Te polycrystal film slowly is gradient to 1.45eV from 2.26eV, expanded the absorption region of solar spectrum greatly, and help to strengthen photo-generated carrier and separate and the internal electric field of collecting having produced one, and then improve the open circuit voltage of battery with the boundary of CdS Window layer contact.

Said second area Cd _1-xZn _xThe component x of Te absorbed layer equals 0, that is to say that second area is the CdTe thin layer, and thickness is the 100-500 nanometer.CdTe is II-VI compounds of group, is the direct band gap material, and its band gap is 1.45eV, and its spectral response and solar spectrum are very identical, and its stable performance, and the absorption coefficient of light is very big.This CdTe thin layer is mainly used in the absorption of enhancing to the sunlight in the solar spectrum peak value scope, improves the short circuit current of battery.

Said the 3rd zone C d _1-xZn _xThe Te absorbed layer is a graded bandgap structure, and by 0 linear gradient to 1, the thickness of this absorbed layer is the 5-100 nanometer to its component x value from CdTe thin layer upper edge thickness direction.The band gap of this zone absorbed layer changes and increases gradually with the x value, causes the quasi-electric field on a direction sensing back of the body surface in the zone, and this electric field can stop electronics surperficial near the back of the body, thereby reduces the back of the body recombination-rate surface of charge carrier.

The advantage of structure of the present invention is: when expanding the solar spectrum absorption region greatly, fully strengthened absorption to sunlight in the solar spectrum peak value scope, improve the open circuit voltage and the short circuit current of battery, thereby significantly improved Solar cell performance.

Description of drawings

Fig. 1 is the Cd with graded bandgap structure of the present invention _1-xZn _xThe cross-sectional view of Te thin-film solar cells.

Fig. 2 is the Cd with graded bandgap structure of the present invention _1-xZn _xThe bandgap structure schematic diagram of Te absorbing layer of thin film solar cell.

Embodiment

Below in conjunction with accompanying drawing the specific embodiment of the present invention is further described.

See Fig. 1, have the Cd of graded bandgap structure _1-xZn _xThe Te thin-film solar cells comprises glass substrate 1, electrode layer 2, n type CdS Window layer 3, p type Cd before the transparent conductive oxide that deposits successively on glass substrate 1 _1-xZn _xTe absorbed layer 4, dorsum electrode layer 5.

Thermal evaporation thickness is electrode layer 2 before ITO, SnO2:F, any transparent conductive oxide among the ZnO:Al of 200～800 nanometers on glass substrate 1.

Magnetron sputtering thickness is the n type CdS Window layer 3 of 50～100 nanometers on preceding electrode layer 2.

P type Cd _1-xZn _xThree zones of Te absorbed layer 4 adopt two target position cosputtering methods to deposit successively on n type CdS Window layer 3, and a target position is ZnTe, and another target position is CdTe, changes the x value of Zn by the sputtering power that changes two targets.Deposit first area Cd earlier _1-xZn _xTe absorbed layer 4-1, thickness are in the 500-1800 nanometer, and component x is from 1 linear gradient to 0; Adopt single target position sputtering method at first area Cd then _1-xZn _xIt is the second area Cd of 100-500 nanometer that Te absorbed layer 4-1 goes up deposit thickness _1-xZn _xTe absorbed layer 4-2, the component x of this absorbed layer is 0, that is to say that this absorbed layer is the CdTe thin layer; Then adopting two target position cosputtering method deposit thickness on the CdTe thin layer again is the three zone C d of the component x of 5-100 nanometer from 0 linear gradient to 1 _1-xZn _xTe absorbed layer 4-3.

The p type Cd for preparing _1-xZn _xTe absorbed layer 4 is placed on and is coated with CdCl ₂And ZnCl ₂In the graphite boat of stratum granulosum, put into tube furnace and anneal.Annealing temperature is at 400-520 ℃, annealing time 20-40 minute.

After the annealing, use thermal evaporation method at Cd _1-xZn _xDeposit the Cu of 3-4 nanometer and the Au dorsum electrode layer 5 of 20-30 nanometer on the Te absorbed layer 4 successively, just can prepare the Cd with graded bandgap structure of high-photoelectric transformation efficiency _1-xZn _xThe Te thin-film solar cells.

Claims

1. the tellurium zincium vestalium thin-film solar cell with graded bandgap structure comprises glass substrate (1), on glass substrate (1), deposit transparent conductive oxide successively before electrode layer (2), n type CdS Window layer (3), p type Cd _1-xZn _xTe absorbed layer (4), dorsum electrode layer (5) is characterized in that:

Said p type Cd _1-xZn _xTe absorbed layer (4) is a first area Cd who is arranged in order on n type CdS Window layer _1-xZn _xTe absorbed layer (4-1), second area Cd _1-xZn _xTe absorbed layer (4-2), the 3rd zone C d _1-xZn _xTe absorbed layer (4-3);

Said first area Cd _1-xZn _xTe absorbed layer (4-1) is a graded bandgap structure, and by 1 linear gradient to 0, the thickness of this absorbed layer is the 500-1800 nanometer to its component x value from CdS Window layer upper edge thickness direction;

Said second area Cd _1-xZn _xThe component x of Te absorbed layer (4-2) equals 0, that is to say that second area is the CdTe thin layer, and thickness is the 100-500 nanometer;

Said the 3rd zone C d _1-xZn _xTe absorbed layer (4-3) is a graded bandgap structure, and by 0 linear gradient to 1, the thickness of this absorbed layer is the 5-100 nanometer to its component x value from CdTe thin layer upper edge thickness direction.