Pulsed current excited transient absorption spectrometer

Abstract

The present disclosure provides a pulsed current excitation transient absorption spectrometer, comprising: a central control unit; a pulse generator configured to generate a current pulse signal under the action of a first trigger signal emitted from the intermediate control unit, so that after the current pulse signal is applied to a sample to be measured, the sample is in a non-radiative excited state of single carrier injection or generates a radiative excited state of an electroluminescence signal; a laser configured to emit a pulsed optical signal under the action of a second trigger signal sent from the intermediate control unit; a beam splitter provided in the light emission direction of the laser, configured to split the pulsed optical signal into a detection optical signal and a reference optical signal, wherein the detection optical signal generates a detection sample optical signal after the detection optical signal is irradiated onto the sample to be measured; a data acquisition unit configured to collect the electroluminescence signal, the detection sample optical signal, and the reference optical signal under the action of a third trigger signal and a fourth trigger signal sent from the central control unit, and process them into electrical signal data reflecting the absorption intensities of optical signals of different wavelengths by the sample at a single time; and a data processing and imaging unit configured to process the electrical signal data to obtain and image a transient absorption signal of the sample to be measured.

Description

[Technical Field]

[0001] The present disclosure relates to the technical field of optical measurements, and in particular to pulsed current excited transient absorption spectroscopy. [Background technology]

[0002] The conventional transient absorption technique is a time-resolved pump-detection technique with wide applications. It uses a pulsed laser to excite a sample under test, changing its physical or chemical properties and thus the sample's absorption coefficient. Another detection light, which may be monochromatic or white light, is configured to detect this change. By changing the delay between the pump light and the detection light, transient absorption spectra can be acquired at different times after the sample is excited by light, and the corresponding kinetic information can be obtained by analyzing the generation and decay of the transient signal. The advantage of the transient absorption spectroscopy technique is that it can study the excited-state kinetics of a sample without the sample emitting light.

[0003] However, due to the lack of related techniques, it is not possible to measure the dynamics information of carriers after electrical excitation completely and accurately. Summary of the Invention

[0004] The present disclosure provides a pulsed current excitation transient absorption spectrometer, comprising: a central control unit configured to emit a trigger signal; a pulse generator configured to generate a current pulse signal under the action of a first trigger signal emitted from an intermediate control unit, and to generate an electroluminescence signal or be in a single-carrier injection non-radiative excited state after the current pulse signal is applied to a sample to be measured; a laser configured to emit a pulsed optical signal under the action of a second trigger signal emitted from the intermediate control unit; a beam splitter disposed in the light emission direction of the laser, configured to split the pulsed optical signal into a detection optical signal and a reference optical signal, wherein the detection optical signal generates a detection sample optical signal after the detection optical signal is irradiated onto the sample to be measured; a data acquisition unit configured to collect the electroluminescence signal, the detection sample optical signal, and the reference optical signal under the action of a third trigger signal and a fourth trigger signal emitted from the central control unit, and process them into electrical signal data reflecting absorption intensities of optical signals of different wavelengths by the sample at a single time; and a data processing and imaging unit configured to process the electrical signal data to obtain and image a transient absorption signal of the sample to be measured.

[0005] Optionally, the sample to be measured is an electro-excited sample, which is placed on a sample stage and connected to the output port of a pulse generator, and it is in an electro-excited state after being connected to a current pulse signal, and emits an electroluminescence signal, or is in a non-radiative excited state of single carrier injection.

[0006] Optionally, the laser is a monochromatic or white light laser.

[0007] Optionally, the frequency of the second trigger signal is 3 / 2 times the frequency of the first trigger signal, and the third and fourth trigger signals are 3 times the frequency of the first trigger signal.

[0008] Alternatively, the intermediate control unit generates a current pulse signal having half the frequency of the first trigger signal to excite the sample to be measured, measures a first current value of the sample to be measured in an electro-excited state when not irradiated with the detection light signal using an ammeter, measures a second current value of the sample to be measured in an electro-excited state when irradiated with the detection light signal using the ammeter, and further adjusts the shape and sequence of the current pulses based on the ratio between the first current value and the second current value, so that the ratio between the magnitude of the even current pulse signal and the magnitude of the odd pulse is the ratio between the first current value and the second current value.

[0009] Optionally, the data collection unit includes a monochromator group including a first monochromator configured to receive the electroluminescence signal and / or the detected sample optical signal and separate the received optical signal into optical signals of different wavelengths, and a second monochromator configured to receive the reference optical signal and separate the reference optical signal into optical signals of different wavelengths; a CCD group including a first CCD and a second CCD configured to process the different wavelength optical signals processed by the first monochromator and the second monochromator, respectively, into electrical signal data reflecting the absorption intensity of the different wavelength optical signals of the sample; and a counter configured to count and store the electrical signals.

[0010] Optionally, a delay device is provided in the intermediate control unit, and the delay device is an optical delay stage or Electronic circuit board The delay device is configured to adjust the time difference between the first trigger signal and the second trigger signal, test information associated with the time change of the absorption signal of the sample to be measured, and adjust and time-divisionally transmit the third trigger signal and the fourth departure signal.

[0011] Optionally, the reference optical signal is configured not to contact the sample to be measured, to eliminate the influence of detected optical signal fluctuations on the measurement.

[0012] Alternatively, the data processing and imaging unit obtains the transient absorption signal ΔOD of the sample to be measured by the following formula:

[0013]

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[0014] where:

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[0015] The pulse current excitation transient absorption spectrometer provided by the present disclosure can alleviate the technical problems of the prior art, such as the inability to effectively measure the dynamics information of carriers after electrical excitation, and its test content is more comprehensive, and it can test the generation and decay dynamics information of transient components of the sample to be measured, as well as the excited state dynamics information, and the sample emission signal excited by the current pulse signal and the detected light Photoconductivity This eliminates the electroluminescence enhancement effect, making the measured transient absorption signal more accurate, and allowing for more accurate and intuitive testing of the carrier dynamics information of the sample being measured. It also adopts a direct electric pulse pump-detection technique, making it more widely applicable to the testing and analysis of fields such as LEDs and solar cells. [Brief explanation of the drawings]

[0016] The drawings are included to provide a further understanding of the present disclosure, constitute a part of the specification, and are used to explain, but not limit, the present disclosure in conjunction with the following specific embodiments.

[0017] [Figure 1]FIG. 1 is a schematic diagram of a pulsed current excited transient absorption spectrometer according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a pulse sequence diagram of a pulse current excited transient absorption spectrometer according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present disclosure provides a pulsed current pump-detector transient absorption spectrometer. Unlike conventional pump-detector transient absorption spectrometers, which excite a sample with light, this spectrometer uses a current pulse signal as the pump source and combines optically or electronically delayed detection light to collect carrier dynamics information in the sample to be measured after electrical excitation. This establishes a pulsed current pump-detector transient absorption spectrometer, which can be used to study parameters such as mobility and defect concentration in devices such as LEDs, electrolasers, photodetectors, and solar cells. It can examine carrier relaxation information excited by a current pulse signal, measure exciton relaxation information, and also examine injected single electron or single hole carrier relaxation information. It can be used to measure absorption spectra and carrier dynamics information corresponding to the generation and decay of transient components in the sample to be measured. An analytical device can detect related information such as excited state energy transfer, charge transfer, and electroacoustic subcoupling in the current-excited sample.

[0019] In the process of realizing the present disclosure, the inventors have discovered that the working principle of a general transient absorption spectrometer based on the transient absorption spectrum technique is as follows: a pulsed laser is incident on a sample as pump light to excite it from the base state to the excited state, and another pulsed monochromatic or white light laser is incident on an optical delay stage or Electronic circuit boardThe detected light is then delayed by a delay and incident on the same position of the sample as the detected light. By controlling the delay time of the detected light relative to the pump light, changes in the sample's absorption spectrum with delay time can be detected, thereby obtaining information on the excited state relaxation of the sample. However, the above-mentioned conventional spectrometers are limited by their photoexcitation mechanism, and carriers can only be generated in the photoabsorption layer, and can only measure the relaxation information of electron-hole pairs. They cannot test the relaxation information of carriers injected or transferred from electrodes, nor can they test the relaxation information of carriers upon single electron or hole injection. However, in research on devices such as LEDs, electrolasers, photodetectors, and solar cells, the above carrier relaxation information can reflect device performance from different perspectives and is equally important and essential. Therefore, the present disclosure provides a transient absorption spectrometer excited by a current pulse signal, and the characteristics of the transient absorption spectrometer excited by a current pulse signal are further described below. Photoconductivity The electroluminescence signal after considering the effect, the detected light signal with and without the current pulse signal pump are collected, and after data processing, the electroluminescence signal and the detected light under the current pulse excitation are calculated. Photoconductivity The electroluminescence increase due to the current increase caused by the effect can be eliminated.

[0020] A feature of the present disclosure is that a current pulse signal is used for excitation and a transient absorption signal of the sample is detected by monochromatic or white light.

[0021] In order to make the objectives, technical solutions and advantages of the present disclosure more apparent, the present disclosure will be further described in detail below in combination with specific embodiments and with reference to the drawings.

[0022] In an embodiment of the present disclosure, a pulsed current excited transient absorption spectrometer is provided, as shown in FIG. 1, the transient absorption spectrometer includes a central control unit configured to issue a trigger signal.

[0023] In an embodiment of the present disclosure, the transient absorption spectrometer further includes an ammeter, which is used to measure the actual current of the sample to be measured.

[0024] In the embodiment of the present disclosure, first, the central control unit generates a current pulse signal with half the frequency of the first trigger signal to excite the sample to be measured, and then the ammeter measures a first current value of the sample to be measured in an electro-excited state when not irradiated with the detection light, and then the ammeter measures a second current value of the sample to be measured in an electro-excited state when irradiated with the detection light signal, and then adjusts the shape and sequence of the current pulse according to the ratio (comparison result) between the first current value and the second current value, and makes the ratio of the magnitude of the even current pulse signal to the magnitude of the odd pulse equal to the ratio of the first current value to the second current value, and generates a pump (current pulse signal) when measuring the transient absorption of the sample to be measured using a pulse generator, and the shape of the current pulse is as shown in Figure 2.

[0025] A pulse generator is configured to generate a current pulse signal under the action of a first trigger signal issued from the central control unit, and to generate an electro-optical signal or be in a non-radiative excited state of single carrier injection after the current pulse signal is applied to the sample to be measured.

[0026] A laser is configured to emit a pulsed light signal upon action of a second trigger signal emitted from the intermediate control unit.

[0027] a beam splitter, disposed in the light emission direction of the laser, configured to split the pulsed light signal into a detection light signal and a reference light signal, where the detection light signal generates a detection sample light signal after the detection light signal is irradiated onto a sample to be measured;

[0028] a data acquisition unit, which is used to collect the electroluminescence signal, the detected sample optical signal, and the reference optical signal under the action of a third trigger signal and a fourth trigger signal issued from the central control unit, and process them into electrical signal data reflecting the absorption intensities of the different wavelength optical signals of the sample at a single time.

[0029] A data processing and imaging unit is configured to process the electrical signal data to obtain and image a transient absorption signal of the sample to be measured.

[0030] The pulse generator is capable of generating square or other shaped current pulse signals of different magnitudes, pulse times and frequencies under the action of the first trigger signal to excite the sample to be measured.

[0031] The sample to be measured is an electro-excited sample, which is placed on the sample stage and connected to the output port of the pulse generator, and it is in an electro-excited state after being connected to a current pulse signal, and emits an electroluminescence signal, or is in a non-radiative excited state of single carrier injection.

[0032] The laser may be a monochromatic laser or a white light laser.

[0033] The reference optical signal is configured to eliminate the influence of fluctuations in the detected optical signal on the measurement.

[0034] The frequency of the second trigger signal is 3 / 2 times the frequency of the first trigger signal.

[0035] The third and fourth trigger signals have three times the frequency of the first trigger signal.

[0036] The data collection unit a monochromator group including a first monochromator and a second monochromator, the first monochromator being adapted to receive the electroluminescence signal and / or the detected sample optical signal and separate the received optical signal into optical signals of different wavelengths, and the second monochromator being adapted to receive the reference optical signal and separate the reference optical signal into optical signals of different wavelengths; a CCD (Charge-coupled Device), including a first CCD and a second CCD, used for processing the different wavelength optical signals processed by the first monochromator and the second monochromator, respectively, into electrical signal data reflecting the absorption intensities of the different wavelength optical signals by a sample; A counter configured to count and store the electrical signals.

[0037] In an embodiment of the present disclosure, the data collection unit further includes a focusing objective lens and an optical fiber.

[0038] The central control unit is provided with a delay device, and the delay device is an optical delay table or Electronic circuit board The delay device is configured to adjust the time difference between the first trigger signal (or the current pulse signal) and the second trigger signal (or the pulsed light signal), thereby testing the time-varying information of the absorption signal of the sample to be measured, and adjust and time-divisionally transmit the third trigger signal and the fourth starting signal to adjust the operation of each component.

[0039] It takes time for the detection light to reach the sample, and there is also a time lag between when the current pulse signal reaches the sample and when the sample is excited. By adjusting this time lag, the time when the actual light signal detects the sample at the start of measurement is just before the actual pulse electrical signal excites the sample.

[0040] In an embodiment of the present disclosure, the monochromatic or white light detection laser is triggered by a trigger signal whose frequency is 3 / 2 times the current pulse frequency, and the emitted pulsed light signal is split into two beams, one of which is irradiated onto the sample to be measured as detection light and the other can be used as reference light, and since the reference light signal does not come into contact with the sample to be measured, it can be arranged to eliminate the problem of temporal jitter of the monochromatic or white light.

[0041] In an embodiment of the present disclosure, the electrical signal data is processed by a data processing and imaging unit, whereby the reference optical signal is used to eliminate the influence of jitter in the detected optical signal to form valid data, and a three-dimensional absorption intensity profile of the sample to be measured with wavelength and time is obtained.

[0042] collected by the data collection unit Photoconductivity After taking into consideration the effect, according to the electroluminescence signal, the optical signal of the detection sample is dispersed by the first monochromator and simultaneously irradiated onto the first CCD, and the reference optical signal is dispersed by the second monochromator and irradiated onto the second CCD, and the first CCD and the second CCD start to collect images upon receiving a third trigger signal from the central control unit, and convert them into electrical signals and transmit them to the counter, and the counter starts to count and store them upon receiving a fourth trigger signal from the central control unit.

[0043] In the embodiment of the present disclosure, the frequency at which the second trigger signal emitted from the intermediate control unit triggers the laser to emit the detection light and the reference light is 3 / 2 times the current pulse frequency emitted by the first trigger signal triggering the pulse generator, so the 6n+1 collection times when the counter starts to collect data are data when there is current pulse signal excitation and detection light signal irradiation, the 6n+4 collection times are data when there is no current pulse signal irradiation and detection light signal irradiation, and the 6n+3 collection times are Photoconductivity is the electroluminescence signal after taking into account the effect, where n is an integer starting from 0, and the transient absorption signal of the sample to be measured excited by the current pulse signal is obtained by the following data processing and imaging unit according to the following formula:

[0044]

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[0045] where:

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[0046] The above is the absorption data of different wavelengths acquired at one time point, and further, by realizing the time difference between the detected light and the pump current pulse signal by a delay device in the central control unit, and performing the step of measuring one or more transient absorption signals, data of the absorption intensity of different wavelengths that changes with time is acquired, and a three-dimensional image of the time-dependent change of the sample to be measured and the absorption intensity of different wavelengths is drawn by the data processing and imaging unit.

[0047] Up to now, the embodiments of the present disclosure have been described in detail with reference to the drawings. It should be noted that any implementation methods not shown or described in the drawings or the specification are known to those skilled in the art and will not be described in detail. Furthermore, the definitions of the above components and methods are not limited to the various specific structures, shapes, or methods mentioned in the embodiments, and those skilled in the art can easily modify or replace them.

[0048] Based on the above description, one skilled in the art should clearly recognize the transient absorption spectrometer of the present disclosure.

[0049] As described above, the present disclosure provides a pulse current excitation transient absorption spectrometer, in which a pulse generator provides a current pulse signal to excite the sample to be measured to emit an electroluminescence signal, or serves as a pump source in a non-radiative excited state of single carrier injection. A monochromatic or white light laser with a frequency 3 / 2 times the current pulse signal frequency is used to generate the detected light signal and the reference light signal. A delay device adjusts the delay between the current pulse signal and the detected light signal. A trigger signal with a frequency 3 times the current pulse frequency is used to trigger a CCD and a counter in a data collection unit, and the data collection unit collects the detected light signal, including the electroluminescence signal, when there is a current pulse. Photoconductivity The electroluminescence signal after calculating the absorption coefficient and the detected light signal without the pump pulse current are collected. Finally, the collected signal is processed by the data processing and imaging unit, and a three-dimensional image of the absorption changes with time and wavelength is formed. The current pulse excitation transient spectrometer detects the electroluminescence signal and the light emitted by the sample under the pulse current excitation. Photoconductivity The additional current due to the effect eliminates the increased luminescence signal and allows the dynamics of electrically injected single electrons, single holes, or electron-hole pairs to be measured.

[0050] Those skilled in the art will appreciate that for convenience and brevity, only the division of the above functional components is taken as an example for description, and in actual application, the above functions can be completed by different functional modules as needed, that is, all or part of the above-described functions can be completed by dividing the internal structure of the chip into different functional modules. The specific operating processes of the above-described chip can be referred to the corresponding processes in the above-described method embodiments, and will not be described here.

[0051] Finally, it should be noted that the above embodiments only illustrate the technical solutions of the present disclosure and do not limit the same. Although the present disclosure has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments or make equivalent substitutions for some or all of the technical features therein. If there is no conflict, the features in the embodiments of the present disclosure can be arbitrarily combined, and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. a central control unit configured to issue a trigger signal; a pulse generator configured to generate a current pulse signal under the action of a first trigger signal issued from the central control unit, so that after the current pulse signal is applied to the sample to be measured, the sample is in a non-radiative excited state of single carrier injection or generates a radiative excited state of an electroluminescence signal; a laser configured to emit a pulsed light signal upon action of a second trigger signal emitted from the central control unit; a beam splitter provided in a light emission direction of the laser and configured to split the pulsed light signal into a detection light signal and a reference light signal, wherein the detection light signal is irradiated onto a sample to be measured, and then a detection sample light signal is generated; a data acquisition unit for acquiring the electroluminescence signal, the detected sample optical signal, and the reference optical signal under the action of a third trigger signal and a fourth trigger signal issued from the central control unit, and processing the electroluminescence signal, the detected sample optical signal, and the reference optical signal into electrical signal data reflecting the absorption intensity of the optical signals of different wavelengths by the sample at a single time; a data processing and imaging unit configured to process the electrical signal data to acquire and image a transient absorption signal of the sample to be measured; The sample to be measured is an electro-excited sample, which is placed on a sample stage and connected to the output port of a pulse generator, and it is in an electro-excited state after being connected to a current pulse signal, and emits an electroluminescence signal, or is in a non-radiative excited state of single carrier injection; The central control unit generates a current pulse signal having a frequency half that of the first trigger signal to excite the sample to be measured, measures a first current value of the sample to be measured in an electro-excited state where the detection light signal is not irradiated by an ammeter, measures a second current value of the sample to be measured in an electro-excited state where the detection light signal is irradiated by the ammeter, and adjusts the shape and sequence of the current pulse based on the ratio between the first current value and the second current value, thereby making the ratio between the magnitude of the even current pulse signal and the magnitude of the odd current pulse signal the ratio between the first current value and the second current value. Pulsed current excited transient absorption spectrometer.

2. The laser is a monochromatic laser or a white light laser.

10. The transient absorption spectrometer of claim 1.

3. The frequency of the second trigger signal is 3 / 2 times the frequency of the first trigger signal, and the frequency of the third trigger signal and the fourth trigger signal is 3 times the frequency of the first trigger signal.

10. The transient absorption spectrometer of claim 1.

4. The data collection unit a monochromator group including: a first monochromator configured to receive the electroluminescence signal and / or the detection sample optical signal and separate the received optical signal into optical signals of different wavelengths; and a second monochromator configured to receive the reference optical signal and separate the reference optical signal into optical signals of different wavelengths; a CCD group including a first CCD and a second CCD configured to process the different wavelength optical signals processed by the first monochromator and the second monochromator, respectively, into electrical signal data reflecting absorption intensities of the different wavelength optical signals by a sample; a counter configured to count and store the electrical signals.

10. The transient absorption spectrometer of claim 1.

5. A delay device is installed in the central control unit, and the delay device can be realized by an optical delay table or an electronic circuit board. The delay device is configured to adjust the time difference between the first trigger signal and the second trigger signal, test information associated with the time change of the absorption signal of the sample to be measured, and adjust and time-divisionally transmit the third trigger signal and the fourth trigger signal.

10. The transient absorption spectrometer of claim 1.

6. The reference light signal does not contact the sample to be measured and is configured to eliminate the influence of variations in the detected light signal on the measurement.

10. The transient absorption spectrometer of claim 1.

7. The data processing and imaging unit obtains the transient absorption signal ΔOD of the sample to be measured by the following formula: [Equation 1] [Equation 2] [Equation 3] [Equation 4] where: [Equation 5] and [Equation 6] are the light intensities of the reference light when there is no current pulse signal excitation and when there is current pulse signal excitation, respectively, and [Equation 7] and [Equation 8] are the light intensity data of the detected light when there is no current pulse signal and when there is a current pulse signal, respectively, i.e. [Equation 9] is the collected data of counter 6n+4 times, [Equation 10] and [0011] are the optical intensities of the pulsed optical signal when there is no current pulse signal and when there is a current pulse signal, respectively, [0012] is the signal data collected by the data collection unit when there is current pulse excitation and when the detection light is irradiated, that is, the data collected by the counter 6n+1 times, [0013] is the current pulse signal electroluminescence signal data collected by the data collection unit after calculating the photoconductive effect, where n is an integer starting from 0, and OD is the absorbance; [0014] is the light intensity of the detected light signal before it passes through the sample, and I is the light intensity of the detected light signal after it passes through the sample.

10. The transient absorption spectrometer of claim 1.

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