System and method for measuring the photothermal conversion efficiency of solid materials

Abstract

The present disclosure relates to a system and method for measuring the photothermal conversion efficiency of solid materials. The system includes: a light source for emitting light; a beam splitter for splitting the light emitted by the light source into two beams of light, one of which irradiates a solid material sample to be measured to heat the sample; a first optical power meter for receiving the other beam of the two beams of light and recording a first optical power value; and an infrared thermal imager for recording the temperature change value of the sample. Wherein, the photothermal conversion efficiency of the sample is calculated based on the first optical power value, the temperature change value and the heat dissipation coefficient of the sample obtained in advance. Since the solid material has a fast and stable heating rate and is less affected by the surrounding environment, the method for measuring the photothermal conversion efficiency of the present invention is faster, more accurate and reliable.

Description

Technical Field

[0001] The present disclosure relates to the field of measurement technologies, and particularly to a system and method for measuring the photothermal conversion efficiency of solid materials. Background Art

[0002] The photothermal conversion phenomenon is a common energy conversion phenomenon in nature. The photothermal conversion phenomenon is utilized in fields such as solar desalination, photothermal therapy, photothermal catalysis, and solar photothermal power generation. The photothermal conversion efficiency is one of the most important indicators for evaluating photothermal conversion, which represents the ratio of the heat generation power of a material to the absorbed light power. Accurately measuring the photothermal conversion efficiency of a material is the basis for evaluating, comparing, and designing photothermal materials.

[0003] In 2007, Roper et al. developed a test method for the photothermal efficiency based on a nano-solution. In a vacuum environment, a nano-gold solution was heated by a laser, and at the same time, a thermocouple was used to measure the temperature at the bottom of the sample cell to obtain the temperature change curve over time. The photothermal conversion efficiency of nano-gold was calculated by fitting the heat dissipation coefficient of the cooling curve. In 2009, Richardson et al. measured the photothermal conversion efficiency of nano-gold solution droplets using a thermocouple. In 2010, Chen et al. added a stirrer to the sample cell to improve the temperature uniformity and measured the photothermal conversion efficiency of nanocrystals such as gold nanorods using a thermocouple. The method of Chen et al. was also adopted in the "Evaluation Method for the Photothermal Effect of Gold Nanorods" (GB / T 320006-2015) drafted by the National Center for Nanoscience and Technology in 2015. In 2014, Wang et al. proposed using "effective mass" to correct the mass problem in the calculation of photothermal efficiency. In 2021, Pasciak et al. experimentally proved the correctness of the "effective mass" correction of Wang et al., as well as the problem that all previous models had a large error in the calculation results due to overestimation of mass.

[0004] However, the above models are all test methods for the photothermal conversion efficiency based on colloidal nanocrystal solutions. The heating rate of the solution is slow and it is easy to evaporate, which will affect the final test results. Moreover, the methods for solving the photothermal conversion efficiency all use single-exponential fitting of the heating curve to obtain the heat dissipation coefficient, and the accuracy is not high. Summary of the Invention

[0005] The present invention innovatively proposes a system and method for measuring the photothermal conversion efficiency of solid materials. Based on the idea of light-heat equivalence, first, in the case of electric heating, the heat dissipation coefficient of the sample is derived by linear fitting using the thermal equilibrium equation, and then, under light heating, the photothermal conversion efficiency of the sample is further solved using the obtained heat dissipation coefficient. Since the solid material has a fast heating rate, is stable, and is less affected by the surrounding environment, the method for measuring the photothermal conversion efficiency of the present invention is faster, more accurate, and reliable.

[0006] According to a first aspect of the present invention, there is provided a system for measuring the photothermal conversion efficiency of a solid material, comprising: a light source for emitting light; a beam splitter for splitting the light emitted by the light source into two beams of light, one of which irradiates a sample of the solid material to be measured to heat the sample; a first optical power meter for receiving the other beam of the two beams of light and recording a first optical power value; and an infrared thermal imager for recording a temperature change value of the sample, wherein the photothermal conversion efficiency of the sample is calculated based on the first optical power value, the temperature change value, and the heat dissipation coefficient of the sample and the absorption rate of the sample to the light emitted by the light source obtained in advance.

[0007] In some alternative embodiments, the system further comprises: a heating resistor and a power source for supplying power thereto, for: before irradiating the sample with the light emitted by the light source, heating the sample with the heating resistor and recording the temperature change value of the sample with the infrared thermal imager to calculate the heat dissipation coefficient of the sample.

[0008] In some alternative embodiments, the voltage of the power source is variable to heat the sample with the heating resistor multiple times at different powers.

[0009] In some alternative embodiments, the system further comprises: a substrate for carrying the sample, wherein the heating resistor and the sample are respectively located on two sides of the substrate.

[0010] In some alternative embodiments, the system further comprises: a second optical power meter for receiving the light transmitted through the sample and recording a second optical power value to determine that the sample reaches light absorption saturation.

[0011] In some alternative embodiments, the light source includes a laser and an LED, and the forms of the sample include nanocrystals, powders, thin films, and small solid pieces.

[0012] According to a second aspect of the present invention, there is provided a method for measuring the photothermal conversion efficiency of a solid material, comprising: emitting light with a light source; splitting the light emitted by the light source into two beams of light with a beam splitter, one of which irradiates a sample of the solid material to be measured to heat the sample; recording a first optical power value of the other beam of the two beams of light; recording a temperature change value of the sample with an infrared thermal imager; and calculating the photothermal conversion efficiency of the sample based on the first optical power value, the temperature change value, and the heat dissipation coefficient of the sample and the absorption rate of the sample to the light emitted by the light source obtained in advance.

[0013] In some alternative embodiments, the method further comprises: recording a second optical power value of the light transmitted through the sample to determine that the sample reaches light absorption saturation.

[0014] In some alternative embodiments, the method further includes: before irradiating the sample with the light emitted by the light source, heating the sample with a heating resistor and recording the temperature change value of the sample with the thermal imager to calculate the heat dissipation coefficient of the sample.

[0015] In some alternative embodiments, the method further includes: changing the voltage of the power supply that powers the heating resistor to heat the sample multiple times at different powers with the heating resistor and recording the temperature change value of the sample with the thermal imager to calculate the heat dissipation coefficient of the sample by linear fitting.

[0016] In some alternative embodiments, the method further includes: using a substrate to carry the sample, with the heating resistor and the sample located on opposite sides of the substrate,

[0017] wherein, when heating the sample with the heating resistor, the temperature change of the sample satisfies the heat balance equation:

[0018]

[0019] wherein, P * is the thermal power of the heating resistor received by the sample, m is the mass of the sample, c is the specific heat capacity of the sample, T E is the overall average temperature of the sample at any moment recorded by the thermal imager when heating the sample with the heating resistor, t is time, H is the heat dissipation coefficient of the sample to the surrounding substrate, and T sur is the average temperature of the substrate surrounding the sample,

[0020] When the sample reaches the thermal equilibrium state, Equation (1) simplifies to:

[0021] P * = HΔT E,max (2)

[0022] wherein, ΔT E,max = T E,max - T sur wherein, T E,max is the maximum average temperature of the sample when it reaches thermal equilibrium when heating the sample with the heating resistor. When the size of the substrate is much larger than the size of the sample, T sur = T amb wherein, T amb is the ambient temperature,

[0023] Heating the sample multiple times at different powers with the heating resistor to obtain multiple P * and ΔT E,maxThe value is used to perform linear fitting using Equation (2) to obtain the heat dissipation coefficient H of the sample to the substrate around it.

[0024] When irradiating the sample with the light emitted by the light source, the temperature change of the sample satisfies the heat balance equation:

[0025]

[0026] where I0 is the first light power value, A is the absorption rate of the sample for the light emitted by the light source obtained in advance, η is the photothermal conversion efficiency of the sample, and T L is the overall average temperature of the sample at any moment recorded by the thermal imager when irradiating the sample with the light emitted by the light source.

[0027] When the sample reaches the thermal equilibrium state, Equation (3) is simplified to:

[0028] I0Aη = HΔT L,max (4)

[0029] where ΔT L,max = T L,max - T sur where T L,max is the maximum average temperature when the sample reaches thermal equilibrium when irradiating the sample with the light emitted by the light source.

[0030] The photothermal conversion efficiency of the sample is obtained from Equation (4):

[0031]

[0032] In some alternative embodiments, the thermal power P of the heating resistor received by the sample is calculated by the following formula * :

[0033]

[0034] where P0 is the electric power output by the power supply to the heating resistor, and P un is the thermal power at the contact surface between the heating resistor and the substrate, S un is the contact area between the heating resistor and the substrate, and S is the surface area of the heating resistor.

[0035] In some alternative embodiments, the absorption rate A of the sample for the light emitted by the light source is calculated by the following formula:

[0036] A = 1 - T - R (7)

[0037] where T is the transmittance of the sample for the light emitted by the light source, and R is the reflectance of the sample for the light emitted by the light source.

[0038] Compared with the prior art, one or more embodiments of the above solution have at least the following advantages or beneficial effects: The present invention innovatively proposes a system and method for measuring the photothermal conversion efficiency of solid materials. Since the heating rate of solid materials is fast and stable, and it is less affected by the surrounding environment, the method for measuring the photothermal conversion efficiency of the present invention is faster, more accurate and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings are used to provide a further understanding of the present disclosure, and constitute a part of the specification. They are used together with the embodiments of the present disclosure to explain the present invention, but do not constitute a limitation to the present disclosure. It should be noted that, for clarity, the components illustrated in the drawings are not necessarily drawn to scale.

[0040] Figure 1 is a schematic layout diagram of a system for measuring the photothermal conversion efficiency of solid materials according to an embodiment of the present invention.

[0041] Figure 2 is a schematic layout diagram of the system when calculating the heat dissipation coefficient of a solid material sample.

[0042] Figure 3 is a temperature photo recorded by an infrared thermal imager when a graphene oxide sample reaches a thermal equilibrium state under heating with an electric power of 0.0318 W.

[0043] Figure 4 is a curve showing the change of the overall average temperature of the sample with time under heating with different electric powers.

[0044] Figure 5 is the fitting result of the heat dissipation coefficient of the sample.

[0045] Figure 6 is a temperature photo recorded by an infrared thermal imager when a sample reaches a thermal equilibrium state under heating with a light power of 0.034 W.

[0046] Figure 7 is a curve showing the change of the overall average temperature of the sample with time under heating with a light power of 0.034 W.

[0047] Figure 8 is the transmittance and reflectance curves of the sample for light of different wavelengths. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The following will describe in detail the embodiments of the present invention with reference to the drawings and embodiments, so as to fully understand how the present invention uses technical means to solve technical problems and the implementation process of achieving technical effects. It should be noted that as long as there is no conflict, the various embodiments in the present invention and the various features in each embodiment can be combined with each other, and the formed technical solutions are all within the protection scope of the present invention.

[0049] Meanwhile, in the following description, many specific details are set forth for the purpose of explanation in order to provide a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details or in a specific manner described herein.

[0050] Figure 1 is a schematic layout of a system for measuring the photothermal conversion efficiency of a solid material according to an embodiment of the present invention. As Figure 1 shown, the system for measuring the photothermal conversion efficiency of a solid material may include: a light source for emitting light; a beam splitter for splitting the light emitted by the light source into two beams of light, one of which irradiates a solid material sample to be measured to heat the sample; a first optical power meter for receiving the other beam of the two beams of light and recording a first optical power value; and a thermal imager for recording the temperature change value of the sample.

[0051] The solid material to be measured may be an organic or inorganic material, and its sample form may be nanocrystals, powders, thin films, or solid pieces, etc., which is different from the traditional solution measurement method.

[0052] The light source may be a laser or an LED, etc., which can emit light of a single wavelength. A broadband light source is also applicable to the present invention, but the calculation is relatively complex, so the present invention preferably uses a single wavelength light source.

[0053] The beam splitter is an optical element that can split light into two identical beams of light at a ratio of 50% to 50%. One of the beams irradiates the sample, and the other beam irradiates the first optical power meter. Therefore, the first optical power value recorded by the first optical power meter is equal to the optical power of the light irradiating the sample.

[0054] The thermal imager is a device for recording the temperature of an object, such as a thermocouple, etc.

[0055] The system for measuring the photothermal conversion efficiency of a solid material may further include a substrate for carrying the sample. The substrate may be a solid such as paper, plastic, or glass that provides support, and the sample may be attached to the substrate. Although Figure 1 the substrate in Figure 1 is placed vertically, in different embodiments, the substrate may also be placed horizontally, that is, rotate

[0056] The system for measuring the photothermal conversion efficiency of a solid material may further include a second optical power meter, which is used to receive the light transmitted through the sample and record the second optical power value to determine that the sample reaches light absorption saturation. If the light intensity of the light irradiating the sample is very low, there may be no transmitted light, and at this time the light is completely absorbed. When the light intensity is gradually increased, the transmitted light can be detected, and at this time the second optical power meter will record the optical power value, indicating that the sample has reached light absorption saturation. Therefore, the role of the second optical power meter is to ensure that the light intensity of the light irradiating the sample is sufficient to make the sample reach light absorption saturation, otherwise the final measurement result of the photothermal conversion efficiency will be inaccurate.

[0057] The system for measuring the photothermal conversion efficiency of a solid material may further include a heating resistor and a power supply for supplying power to it, which are used for: before irradiating the sample with the light emitted by the light source, using the heating resistor to heat the sample and using an infrared thermal imager to record the temperature change value of the sample to calculate the heat dissipation coefficient of the sample. The power supply is, for example, voltage variable to heat the sample multiple times with the heating resistor at different powers. Figure 2 It is a schematic diagram of the system layout when calculating the heat dissipation coefficient of the sample. As Figure 2 shown, the heating resistor and the sample are located on both sides of the substrate respectively. After turning on the power supply and using the heating resistor to heat the sample, the temperature change of the sample at this time satisfies the heat balance equation:

[0058]

[0059] where P * is the thermal power of the heating resistor received by the sample, m is the mass of the sample, c is the specific heat capacity of the sample, both m and c can be obtained in advance, T E is the overall average temperature of the sample at any moment recorded by the infrared thermal imager when heating the sample with the heating resistor, which can be obtained through the infrared thermal imager, t is the time, H is the heat dissipation coefficient of the sample to the surrounding substrate, and T sur is the average temperature of the substrate around the sample.

[0060] When the sample reaches the thermal equilibrium state, Equation (1) can be simplified to:

[0061] P * =HΔT E,max (2)

[0062] where ΔT E,max =T E,max -T sur where T E,max is the maximum average temperature when the sample reaches thermal equilibrium when heating the sample with the heating resistor. When the size of the substrate is much larger than the size of the sample, there is T sur =T amb where T amb is the ambient temperature.

[0063] By changing the voltage of the power supply, the heating resistor can be used to heat the sample multiple times at different powers to obtain multiple P * and ΔT E,max values. Thus, by performing a linear fit using Equation (2), the heat dissipation coefficient H of the sample with respect to the surrounding substrate can be obtained. The H obtained in this way is more accurate than the value obtained through single heating.

[0064] Then, the power supply and the heating resistor are removed, and the sample is irradiated with light emitted by a light source. The system is arranged as shown Figure 1 schematically. At this time, the temperature change of the sample satisfies the heat balance equation:

[0065]

[0066] where I0 is the first optical power value recorded by the first optical power meter, A is the absorption rate of the sample for the light emitted by the light source obtained in advance, η is the photothermal conversion efficiency of the sample, and T L is the overall average temperature of the sample at any moment recorded by the thermal imager when the sample is irradiated with the light emitted by the light source, which can be obtained through the thermal imager.

[0067] When the sample reaches the thermal equilibrium state, Equation (3) can be simplified to:

[0068] I0Aη = HΔT L,max (4)

[0069] where ΔT L,max = T L,max - T sur , where T L,max is the maximum average temperature of the sample when it reaches thermal equilibrium when irradiated with the light emitted by the light source.

[0070] From Equation (4), the photothermal conversion efficiency of the sample can be obtained:

[0071]

[0072] In Equation (2), the thermal power P * received by the sample from the heating resistor can be obtained in advance. For example, it can be calculated by the following formula:

[0073]

[0074] where P0 is the electric power output by the power supply to the heating resistor, P un is the thermal power at the contact surface between the heating resistor and the substrate, S un is the contact area between the heating resistor and the substrate, and S is the total surface area of the heating resistor. P0, S un , and S can be obtained from the known conditions, and thus P * can be obtained.

[0075] In formula (5), the light absorption rate A of the sample to the light emitted by the light source can be obtained in advance. For example, it can be calculated by the following formula:

[0076] A = 1 - T - R (7)

[0077] Wherein, T is the light transmittance of the sample to the light emitted by the light source, and R is the light reflectance of the sample to the light emitted by the light source. T and R can be obtained from the transmittance and reflectance curves of the sample to light of different wavelengths, and thus A can be obtained.

[0078] The following is a specific example to more intuitively illustrate the method for measuring the photothermal conversion efficiency of solid materials according to the present invention, but the present invention is not limited to this specific example.

[0079] In this example, the light source is a continuous laser with a wavelength of 980 nm, and its power is adjustable between 0 and 200 mW. Both optical power meters are PM100USB. The thermal imager is FLIR A700, and its test temperature range is -20 to 150 °C. The sample is prepared from commercially available graphene oxide sol (Aladdin). The substrate is filter paper. The reason for choosing filter paper is that the filter paper is thin and has a large area, so it better meets the above assumption conditions: when the size of the substrate is much larger than the size of the sample, there is T sur = T amb ; and the filter paper is porous and is easy for nanocrystals or powders to adhere to. The preparation method of the sample is to drop the graphene oxide sol on the filter paper and then fully dry it naturally in the air. The heating resistor is a cylindrical thin-film resistor with a thickness of 1 mm, a diameter of 5 mm, and a resistance value of 1.25 Ω. The output voltage range of the variable voltage power supply is 0 - 36 V.

[0080] First, the resistor is closely attached to the substrate, the electric power P0 output by the power supply to the resistor is set to 0.0318 W, the power supply is turned on, and the thermal imager is used to monitor the change of the overall average temperature of the sample over time. The temperature photo recorded by the thermal imager when reaching the thermal equilibrium state is as Figure 3 shown.

[0081] The electric power P0 is changed to 0.05025 W, 0.072 W, 0.0973 W, and 0.1248 W respectively, and a total of five groups of curves of the overall average temperature of the sample changing with time are obtained, as Figure 4 shown. From this, the maximum temperature rise ΔT of the sample can be calculated respectively E,max T E,max - T sur . At the same time, P * = 0.357P0 is calculated by formula (6). Thus, the heat dissipation coefficient H can be obtained by fitting according to formula (2), and the fitting result is as Figure 5 shown, H = 0.00317 W / °C.

[0082] Then, remove the power supply and the resistor, set the optical power I0 = 0.034 W, turn on the laser, monitor the change of the overall average temperature of the sample over time, and when it reaches the thermal equilibrium state, the temperature photo recorded by the thermal imager is as shown in Figure 6 Figure. The curve of the overall average temperature of the sample changing with time is as shown in Figure 7 Figure. From this, the maximum temperature rise ΔT of the sample can be calculated L,max = T L,max - T sur .

[0083] The transmittance and reflectance curves of the sample can be measured by a Lambda 1050+ spectrophotometer, and the results are as shown in Figure 8 Figure. Combining with Equation (7), the absorption rate A of the sample for 980 nm light can be obtained as 54.8%.

[0084] Finally, the photothermal conversion efficiency of the sample can be obtained from Equation (5), and the result is 89.8%.

[0085] The present invention innovatively proposes a system and method for measuring the photothermal conversion efficiency of solid materials. Based on the idea of light - heat equivalence, first, in the case of electric heating, the heat dissipation coefficient of the sample is deduced by making a linear fit using the thermal equilibrium equation, and then, under light heating, the photothermal conversion efficiency of the sample is further solved using the obtained heat dissipation coefficient. Since the solid material has a fast heating rate, is stable, and is less affected by the surrounding environment, the method for measuring the photothermal conversion efficiency of the present invention is faster, more accurate, and reliable.

[0086] It should be understood that the embodiments disclosed in the present invention are not limited to the specific processing steps or materials disclosed herein, but should extend to equivalent alternatives of these features understood by those of ordinary skill in the relevant art. It should also be understood that the terms used herein are only for the purpose of describing specific embodiments and do not mean to limit.

[0087] The "embodiments" mentioned in the specification mean that the specific features or characteristics described in combination with the embodiments are included in at least one embodiment of the present invention. Therefore, the phrase "embodiments" appearing throughout the specification does not necessarily refer to the same embodiment.

[0088] Although the disclosed embodiments of the present invention are as above, the content described is only an embodiment adopted for the convenience of understanding the present invention and is not used to limit the present invention. Any person skilled in the technical field to which the present invention pertains, without departing from the spirit and scope disclosed by the present invention, can make any modifications and changes in the form of implementation and details, but the protection scope of the present invention must still be subject to the scope defined by the appended claims.

Claims

1. A system for measuring the photothermal conversion efficiency of a solid material, comprising: A light source for emitting light; A beam splitter for splitting the light emitted by the light source into two beams of light, one of which irradiates a solid material sample to be measured to heat the sample; A first optical power meter for receiving the other beam of the two beams of light and recording a first optical power value; And An infrared thermal imager for recording the temperature change value of the sample, Wherein, the photothermal conversion efficiency of the sample is calculated based on the first optical power value, the temperature change value, and the pre-obtained heat dissipation coefficient of the sample and the absorption rate of the sample to the light emitted by the light source, Wherein, the system further comprises: A heating resistor and a power supply for powering it, for: before irradiating the sample with the light emitted by the light source, heating the sample with the heating resistor and recording the temperature change value of the sample with the infrared thermal imager to calculate the heat dissipation coefficient of the sample.

2. The system according to claim 1, wherein, The voltage of the power supply is variable to heat the sample multiple times at different powers with the heating resistor.

3. The system according to claim 1, further comprising: A substrate for carrying the sample, the heating resistor and the sample are respectively located on both sides of the substrate.

4. The system according to claim 1, further comprising: A second optical power meter for receiving the light transmitted through the sample and recording a second optical power value to determine that the sample reaches light absorption saturation.

5. The system according to claim 1, wherein The light source includes a laser and an LED, and the forms of the sample include nanocrystals, powders, thin films, and solid small pieces.

6. A method for measuring the photothermal conversion efficiency of a solid material, comprising: Emitting light with a light source; Splitting the light emitted by the light source into two beams of light with a beam splitter, one of which irradiates a solid material sample to be measured to heat the sample; Recording the first optical power value of the other beam of the two beams of light; Recording the temperature change value of the sample with an infrared thermal imager; And Calculating the photothermal conversion efficiency of the sample based on the first optical power value, the temperature change value, and the pre-obtained heat dissipation coefficient of the sample and the absorption rate of the sample to the light emitted by the light source, Wherein, the method further comprises: before irradiating the sample with the light emitted by the light source, heating the sample with a heating resistor and recording the temperature change value of the sample with the infrared thermal imager to calculate the heat dissipation coefficient of the sample.

7. The method according to claim 6, further comprising: Recording the second optical power value of the light transmitted through the sample to determine that the sample reaches light absorption saturation.

8. The method according to claim 6, further comprising: Changing the voltage of the power supply for powering the heating resistor to heat the sample multiple times at different powers with the heating resistor and recording the temperature change value of the sample with the infrared thermal imager to calculate the heat dissipation coefficient of the sample by linear fitting.

9. The method according to claim 8, further comprising: Carrying the sample with a substrate, the heating resistor and the sample are respectively located on both sides of the substrate, Wherein, when heating the sample with the heating resistor, the temperature change of the sample satisfies the heat balance equation: where P * is the thermal power of the heating resistor received by the sample, m is the mass of the sample, c is the specific heat capacity of the sample, and T E is the overall average temperature of the sample at any moment recorded by the thermal imager when heating the sample with the heating resistor, t is time, H is the heat dissipation coefficient of the sample to the substrate around it, and T sur is the average temperature of the substrate around the sample When the sample reaches the thermal equilibrium state, Equation (1) is simplified to: P * =HΔT E,max (2) where, ΔT E,max = T E,max - T sur , where, T E,max is the maximum average temperature of the sample when it reaches thermal equilibrium while heating the sample with the heating resistor. When the size of the substrate is much larger than the size of the sample, T sur = T amb , where, T amb is the ambient temperature Heat the sample multiple times with the heating resistor at different powers to obtain multiple P * and ΔT E,max values, and perform linear fitting using Equation (2) to obtain the heat dissipation coefficient H of the sample to the substrate around it. When irradiating the sample with the light emitted by the light source, the temperature change of the sample satisfies the heat balance equation: where I0 is the first optical power value, A is the absorption rate of the sample for the light emitted by the light source obtained in advance, η is the photothermal conversion efficiency of the sample, and T L is the overall average temperature of the sample at any moment recorded by the thermal imager when the sample is irradiated with the light emitted by the light source When the sample reaches the thermal equilibrium state, Equation (3) is simplified to: I0Aη=HΔT L,max (4) where ΔT L,max = T L,max - T sur , where T L,max is the maximum average temperature when the sample reaches thermal equilibrium when the sample is irradiated with the light emitted by the light source The photothermal conversion efficiency of the sample is obtained from Equation (4):

10. The method according to claim 9, wherein, The thermal power P of the heating resistor received by the sample is calculated by the following formula * :[[]]END]] Among them, P0 is the electric power output by the power supply to the heating resistor, and P un is the thermal power of the contact surface between the heating resistor and the substrate, S un is the contact area between the heating resistor and the substrate, and S is the surface area of the heating resistor.

11. The method according to claim 9, wherein, The absorbance A of the sample for the light emitted by the light source is calculated by the following formula: A = 1 - T - R (7) where T is the transmittance of the sample for the light emitted by the light source, and R is the reflectance of the sample for the light emitted by the light source.

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