RTP heating system and method

An RTP heating system and an RTP heating method, which can heat a photovoltaic-device intermediate product having a glass substrate, a Mo layer, and a light absorption layer in formation. The RTP heating system is composed of a chamber; a support member located in the chamber; a heating element mounted in the chamber for emitting infrared rays for heating; and a plurality of temperature sensors and a temperature control device for sensing and controlling thermal sources from the heating element and the support member. The infrared rays can be mostly reflected off the Mo layer to apply less direct heating to the glass substrate. Accordingly, the upper and lower surfaces of the photovoltaic-device intermediate product can be heated under different temperatures separately to prevent the glass substrate below the photovoltaic-device intermediate product from softening and deformation and to allow production of the light absorption layer on the Mo layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to manufacturing technology of photovoltaic devices, and more particularly, to a rapid temperature process (RTP) heating system and an RTP heating method.

2. Description of the Related Art

The existing photovoltaic devices are usually made by that a Mo layer is disposed on a glass substrate and a light absorption layer, e.g. copper indium gallium selenide (CIGS) layer or copper indium selenide (CIS) layer, is produced on the Mo layer. When it is intended to produce the light absorption layer, the temperature needs to be heightened up to 500° C. and higher, and then the light absorption layer can be formed on the Mo layer by sputtering, vapor deposition, electroplating, or inkjet.

In the process of production of the above-mentioned light absorption layer, the method of heightening the temperature includes the popular RTP is to heat photovoltaic devices by a thermal source located above the photovoltaic devices. The thermal source can be a resistance-type heating wire or an infrared heater for heating the upper surface of the photovoltaic devices.

In the Paragraph [0013] of the specification of the U.S. Pat. Pub. No. 2008/0305247, it mentioned that German Pat. No. 19936081A1 disclosed a conventional RTP for manufacturing a CIS or CIGS layer.

U.S. Pat. Pub. No, 2009/0305455 disclosed an RTP which is to heat the upper and lower surfaces of the photovoltaic devices by an infrared lamp under the temperature of 200-600° C. However, the photovoltaic devices are made of aluminum rather than glass.

When the light absorption layer is manufactured by the RTP, if the substrate is made of glass, there will be a problem. For example, when the light absorption (CIGS) layer is manufactured, the optimal temperature is 500° C. and higher and the deformation temperature of the glass is 510° C. or so, such that the glass substrate below the CIGS layer will be softened for deformation and the whole photovoltaic devices will become unusable due to such deformation. Perhaps, that may be why the substrate is made of aluminum in the U.S. Pat. Pub. No, 2009/0305455.

As can be seen from the above, in the existing temperature control technology, it is very difficult so far to integrate the manufacturing temperature (500° C. and higher) of the light absorption layer and the deformation temperature (510° C.) of the glass on the glass substrate to allow the light absorption layer to be manufactured on the glass.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide an RTP heating system, which can apply heating of different temperatures to the upper and lower surfaces of the photovoltaic devices having the glass substrate to allow the upper surface to meet the requirement for manufacturing temperature of the light absorption layer and to prevent the heat of the lower surface from softening and deforming the glass substrate in such a way that the light absorption layer can be manufactured on the glass substrate.

The secondary objective of the present invention is to provide an RTP heating method, which can manufacture the light absorption layer on the glass substrate without softening and deforming the glass substrate.

The foregoing objectives of the present invention are attained by the RTP heating system, which can heat a photovoltaic-device intermediate product having a glass substrate, a Mo layer coated onto the glass substrate, and a light absorption layer in formation. The RTP heating system is composed of a chamber, a support member, at least one heating element, a plurality of temperature sensors, and a temperature control device. The chamber can accommodate a photovoltaic-device intermediate product therein. The support member is located below the chamber for supporting and heating the photovoltaic-device intermediate product. The at least heating element is mounted in the upper side of the chamber for emitting infrared rays to heat the upper surface of the photovoltaic-device intermediate product. The infrared rays emitted by the heating element are each limited to a predetermined wavelength and thus can be mostly reflected off the Mo layer to apply less direct heating to the glass substrate and to apply more direct heating to the light absorption layer in formation. The temperature sensors are mounted inside the chamber for sensing the temperature of the upper and lower surfaces of the photovoltaic-device intermediate product. The temperature control device is connected with the temperature sensors, the heating element, and the support member for controlling heat sources emitted from the element and through the support member.

The foregoing objectives of the present invention are attained by the RTP heating method, which is to heat a photovoltaic-device intermediate product having a glass substrate and a Mo layer coated onto the glass substrate. The RTP heating method includes the steps of placing the photovoltaic-device intermediate product on a support member, then heating an upper surface of the photovoltaic-device intermediate product by a heating element, and finally heating a lower surface of the photovoltaic-device intermediate product through the support member. The heating element can emit infrared rays, each of which is limited to a predetermined wavelength, to heat the upper surface of the photovoltaic-device intermediate product in such a way that most of the heat is reflected by the Mo layer to apply less direct heating to the glass substrate and to apply more direct heating to the light absorption layer. In this way, the heating degree can be controlled to make the temperature of the upper surface of the photovoltaic-device intermediate product be higher than deformation temperature of the glass substrate and to make the temperature of the lower surface of the photovoltaic-device intermediate product be lower than the deformation temperature of the glass substrate. Besides, the upper and lower surfaces of the photovoltaic-device intermediate product can be heated under different temperatures separately to prevent the glass substrate below the photovoltaic-device intermediate product from softening and deformation and to allow production of the light absorption layer on the Mo layer.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring toFIGS. 1-3, an RTP heating system10constructed according to a first preferred embodiment of the present invention for heating a photovoltaic-device intermediate product51, which includes a glass substrate52, a Mo layer54coated on the glass substrate52, and a light absorption layer56in formation, is composed of a chamber11, a support member12, a plurality of heating elements22, a plurality of temperature sensors32, and a temperature control device42. The detailed descriptions and operations of these elements as well as their interrelation are recited in the respective paragraphs as follows.

The chamber11can accommodate the photovoltaic-device intermediate product51therein. The support member12has good thermal conductivity and high specific heat and is located in a lower side of the chamber11for supporting the photovoltaic-device intermediate product51and heating its upper surface, i.e. the upper surface of the glass substrate52. In this embodiment, the support member12includes a lower thermal source14for heating the lower surface of the glass substrate52. Besides, an external surface of the support member12falls within the lower surface of the photovoltaic-device intermediate product51. The lower thermal source14can be a heating wire, an infrared lamp, and so on, and it is a heating wire in this embodiment, as shown inFIG. 1. The support member12in this embodiment, for example, has specific heat more than 250 J/Kg.° C., thermal conductivity more than 1.5 W/m° C., and coefficient of thermal expansion less than 1.2×10−7/° C. at 30-750° C.

The support member12further includes a strut16of low thermal conductivity for covering a periphery thereof.

The heating elements22are infrared heaters mounted in the upper side of the chamber11for emitting infrared rays downwardly to heat the upper surface of the photovoltaic-device intermediate product51, i.e. the light absorption layer56in formation on the Mo layer54. The infrared rays emitted by the heating elements22are each limited to a predetermined wavelength to be mostly reflected by the Mo layer54to apply less direct heating to the glass substrate52and to apply more direct heating to the light absorption layer56in formation. Each of the infrared rays has a wavelength of 3500-4500 Å, and the reflected part of the infrared rays by the Mo layer54is more than 80%. The support member12is covered by the strut16to avoid irradiation of the infrared rays.

The temperature sensors32are mounted in the chamber11for sensing the temperatures of the upper and lower surfaces of the photovoltaic-device intermediate product51.

The temperature control device42is connected with the temperature sensors32, the heating elements33, and the lower thermal source14of the support member12for controlling the thermal source emitted by the heating element22and through the support12.

When it is intended to manufacture the light absorption layer56on the Mo layer54, it is necessary to heighten the temperature. When the heating proceeds, the heating elements22and the lower thermal source14can be operated to heat the upper and lower surfaces of the photovoltaic-device intermediate product51. Because most of the infrared rays of the heating elements22can reflect off the Mo layer, the glass substrate52below the Mo layer54is less directly heated. However, to avoid too much difference between the temperature of the light absorption layer56and that of the glass substrate52, the lower thermal source14must be operated to heat the glass substrate52to heighten the temperature of the glass substrate52. When the heating proceeds, the temperature control device42is operated to control and make the temperature of the upper surface of the photovoltaic-device intermediate product51be higher than that of the lower surface thereof. For example, the temperature of the upper surface is 500° C. and higher, and the temperature of the lower surface is 425° C. and higher. In this way, the temperature of the upper surface is sufficient for producing the light absorption layer56, e.g. CIGS layer, and the temperature of the lower surface is lower than 510° C., such that the glass substrate52will not be softened and deformed.

In addition, the low thermal conductivity of the strut16can isolate the thermal energy emitted by the heating elements22from the strut16to prevent the thermal energy from directly heating the support member12, such that the temperature of the support member12can be simply controlled without being interfered by the heating elements22.

Furthermore, after the support member12is heated up to the required temperature, the lower thermal source14can be stopped from heating the support member12, and the good thermal conductivity of the support member12provides thermal dissipation instead. High specific heat can result in less variation of the temperature to prevent the temperature of the support member12from rising subject to that of the glass substrate52in such a way that the lower surface of the glass substrate52can be thermally dissipated through the support member12, thus resulting in that the temperature of the glass substrate52is not higher than the deformation temperature.

Referring toFIG. 1again, an RTP heating method in accordance with a second preferred embodiment of the present invention for heating a photovoltaic-device intermediate product51having a glass substrate52, a Mo layer54coated on the glass substrate52, and a light absorption layer56in formation includes the following steps.

a) Put the photovoltaic-device intermediate product51on a support member12.

b) Heat an upper surface (i.e. the light absorption layer on the Mo layer54in formation) of the photovoltaic-device intermediate product51by a heating element22and then heat a lower surface (i.e. the lower surface of the glass substrate52) of the photovoltaic-device intermediate product51through the support member12. The heating element22can generate infrared rays to heat the upper surface of the photovoltaic-device intermediate product51. Each of the infrared rays is limited to a predetermined wavelength of 3500-4500 Å, such that most of the infrared rays can be reflected off the Mo layer54to decrease direct heating applied to the glass substrate52and to mainly heat the light absorption layer56in formation. In this way, the heating degree can be controlled to allow the temperature of the upper surface of the photovoltaic-device intermediate product51to be higher than the deformation temperature of the glass substrate52and to allow the temperature of the lower surface of the photovoltaic-device intermediate product51to be lower than the deformation temperature of the glass substrate52. In this embodiment, in the process of the heating, the photovoltaic-device intermediate product51is heated up to 500° C. and higher and its lower surface is heated up to 425° C. and higher.

The heating method of the second embodiment takes advantages of the characteristic that the Mo layer54can reflect the infrared rays to isolate and prevent most of the infrared rays from directly heating the glass substrate52to further heat the upper and lower surfaces of the photovoltaic-device intermediate product51separately.

Referring toFIG. 2in view ofFIG. 4, an RTP heating method in accordance with a third preferred embodiment of the present invention is to heat a photovoltaic-device intermediate product51′ having a glass substrate52′, a Mo layer54′ coated on the glass subset52′, and a light absorption layer56′ in formation includes the following steps.

a) Preheat the photovoltaic-device intermediate product51′ externally and then send it into the chamber11′ under the condition that the photovoltaic-device intermediate product51′ remains a predetermined temperature, 425° C. in this embodiment. Alternatively, the photovoltaic-device intermediate product51′ can be preheated in another chamber (not shown) before sent to the chamber11′.

b) Put the photovoltaic-device intermediate product51′ on a support member12′ having good thermal conductivity and high specific heat.

c) Heat an upper surface (i.e. the light absorption layer on the Mo layer54′ in formation) of the photovoltaic-device intermediate product51′ by a heating element22′ and then thermally conduct a lower surface (i.e. the lower surface of the glass substrate52′) of the photovoltaic-device intermediate product51′ through the support member12′ for thermal dissipation. The heating element22′ can generate infrared rays to heat the upper surface of the photovoltaic-device intermediate product51′. Each of the infrared rays is limited to a predetermined wavelength of 3500-4500 Å, such that most of the infrared rays can be reflected off the Mo layer54′ to decrease direct heating applied to the glass substrate52′ and to mainly heat the light absorption layer56′ in formation. In this way, the upper surface of the photovoltaic-device intermediate product51′ can be heated and the temperature of the Mo layer54′ can rise due to the heating to a certain extent to be transmitted to the glass substrate52′, such that the substrate52′ is heated to raise its temperature. The heat in the glass substrate52′ can be further transmitted to the support member12′ for thermal dissipation to lower the temperature of the substrate52′, such that the lower surface of the glass substrate52′ can keep thermal dissipation and then the temperature of the glass substrate52′ can be lower than the deformation temperature.

In the third embodiment, in the step c), the upper surface of the photovoltaic-device intermediate product51′ is heated up to 500° C. and higher and the lower surface of the photovoltaic-device intermediate product51′ is thermally dissipated down to 500° C. and lower.

The heating method of the third embodiment takes advantages of the characteristic that the Mo layer54can reflect the infrared rays to isolate and prevent most of the infrared rays from directly heating the glass substrate52to further heat the upper surface of the photovoltaic-device intermediate product51′ other than the lower surface directly. Besides, the heat of the lower surface can be dissipated through the support member, such that it will not happen that the glass substrate52′ is softened and deformed.

In conclusion, the present invention includes the following advantages and effects.

1. The heating of different temperatures can be applied to the upper and lower surfaces of the photovoltaic-device intermediate product to allow the temperature of the upper surface to meet the requirement for production of the light absorption layer and prevent the heat of the lower surface from softening and deforming the glass substrate. In this way, the light absorption layer can be produced on the glass substrate.

2. Under the condition that the glass substrate is not softened and deformed, the light absorption layer can be produced on the glass substrate.

Although the present invention has been described with respect to specific preferred embodiments thereof, it is in no way limited to the specifics of the illustrated structures but changes and modifications may be made within the scope of the appended claims.