Patent Publication Number: US-2012032687-A1

Title: Detection apparatus for detecting electric field distribution or carrier distribution based on the intensity of high-order harmonics

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a detection apparatus for detecting an electric field distribution or a carrier distribution on the basis of the intensity of high-order harmonics. 
     2. Description of the Related Art 
     In the field of electronic engineering, it is very important to clarify dynamic characteristics of carriers in an object. Various methods (such as TOF method explained later) have hitherto been developed to evaluate dynamic characteristics of carriers. On the other hand, a method for inputting a fundamental wave and measuring mobility of carriers based on high-order harmonics thereof has been developed. 
     In recent years, organic electronic devices using organic materials such as organic illumination, organic solar cells, organic FETs (Field Effect Transistors), and the like particularly attracted attention. This is because the organic electronic devices have characteristics such as flexibility, which are different from those of ordinary electronic devices. Also in these organic electronic devices, it is very important to evaluate dynamic characteristics of carriers when devices and the like are developed. The dynamic characteristics of carriers mean various characteristics such as carrier injection, carrier accumulation, carrier transport, carrier generation, and disappearance. 
     TOF (Time of Flight) method, i.e., one of methods for evaluating dynamic characteristics of carriers (in particular, mobility of carriers), will be hereinafter explained. 
       FIG. 18  is an explanatory diagram for illustrating the TOF method. In the TOF method, as shown in  FIG. 18 , a power supply E 1  is used to apply a voltage to a sample  203  held between a pair of electrodes  200 ,  201 . Laser light is emitted to the sample  203  from the side of the electrode  200  when the voltage is applied to the sample. The emitted laser light generates electrons in proximity to the electrode  200  in the sample  203 . The generated electrons proceed toward the electrode  201  according to an electric field. Then, an ampere meter  202  connected to the electrode  201  measures the amount of electric current between the electrode  201  and the ground. The electrode  200  is transparent to the laser light. Based on the configuration, mobility of carriers is obtained as follows. First, a traveling time of carriers between the electrodes is obtained based on the measured waveform of the electric current, and the mobility of carriers is obtained based on the obtained traveling time of carriers and the distance between the electrodes set in advance. Japanese Patent Application Laid-Open No. 2006-135125 describes an apparatus used for the TOF method. 
     A method for measuring a carrier distribution includes an SHG (Second-Harmonic Generation) method. As shown in  FIG. 17 , this employs the detection method based on the intensity of the second harmonic of light. In this method, an emission unit and a detection unit are provided. The emission unit emits a fundamental wave onto an object to be observed. The detection unit detects the second harmonic generated according to an electric field distribution or a carrier distribution during application of a voltage. A control unit for driving the emission unit and the detection unit controls a time interval of oscillation and a detection signal, so as to detect the mobility of carriers. 
     Operation of this method will be explained with reference to  FIG. 17 .  FIG. 17  is a schematic configuration diagram illustrating a detection apparatus (hereinafter simply referred to as an SHG intensity distribution obtaining apparatus)  100  for the second harmonic (high-order harmonics) used for observing an electric field distribution or a carrier distribution. 
     The conventional detection apparatus detects, on the basis of the intensity of the second harmonic, an electric field distribution or a carrier distribution between electrodes provided in an object to be observed. The conventional detection apparatus includes an emission unit for emitting a reference wave onto the object, a detection unit for detecting the second harmonic generated according to the electric field distribution or the carrier distribution during application of a voltage, a signal for controlling the fundamental wave, and a signal for controlling the voltage. The intervals therebetween are configured to be changeable, so that the conventional detection apparatus detects the mobility. 
     As shown in  FIG. 17 , the SHG intensity distribution obtaining apparatus  100  includes a laser oscillator (light source)  1 , a wavelength converter  2 , a mirror RM, an attenuation filter  3 , a polarizer  4 , a low pass filter  5 , a half mirror HM 1 , and an objective lens OL. In addition, the SHG intensity distribution obtaining apparatus  100  includes a stage  11  on which a pentacene FET (object to be observed)  50  is placed. In addition, the SHG intensity distribution obtaining apparatus  100  includes a half mirror HM 2 , a band-pass filter  12 , a polarizer  13 , a band-pass filter  14 , and a photomultiplier tube (PMT)  15 . In addition, the SHG intensity distribution obtaining apparatus  100  includes a lens  17  and an image capturing device  18 . In addition, the SHG intensity distribution obtaining apparatus  100  includes a control signal output unit  30  and a processing unit  16 . 
     In the SHG intensity distribution obtaining apparatus  100 , laser light (fundamental wave) excited by the laser oscillator  1  and output from the wavelength converter  2  is emitted onto the pentacene FET  50 . The photomultiplier tube  15  detects the second harmonic generated by the pentacene FET  50 . The control signal output unit  30  controls a time when a pulse signal S 2  is output to a source electrode  6  of the pentacene FET  50 , and controls a time when a pulse signal S 3  is output to a switch device  21 . Therefore, it is possible to change the time when the voltage is actually applied to the pentacene FET  50  (the first point in time=voltage application time) and the time when the laser is emitted onto the pentacene FET  50  (the second point in time=laser emission time). After the pulse signal S 3  is output to the switch device  21 , the laser oscillator  1  outputs laser light. 
     For each of a plurality of portions of channels that may be formed in the pentacene FET  50  (carrier transport passage), the intensity distribution of the second harmonic is measured using the SHG intensity distribution obtaining apparatus  100  under a plurality of conditions in each of which a time interval between the voltage application time and the laser emission time is different. As a result, transition of the electric field distribution or the carrier distribution in the channels of the pentacene FET  50  can be observed. 
     The laser oscillator  1  includes a flash lamp (excitation light source)  19 , a rod  20 , a switch device (switch unit)  21 , reflection mirrors M 1 , M 2 , and a THG (Third Harmonic Generation) crystal  22 . The laser oscillator  1  is a so-called solid laser device operating in Q-switching mode. The laser oscillator  1  outputs laser light (fundamental light or fundamental wave) having a predetermined pulse width. The laser oscillator  1  outputs laser light having a wavelength of 355 nm. The laser oscillator  1  serves not only as a light source but also as an emission unit. 
     The flash lamp  19  is a pumping excitation light source. The rod  20  is a material doped with Nd:YAG (laser medium). The reflection mirror M 1  is provided at one side of the rod  20 . The reflection mirror M 2  is provided at the other side of the rod  20 . An oscillator is constituted by the rod  20  and the reflection mirrors M 1 , M 2 . The switch device  21  is provided between the rod  20  and the reflection mirror M 1 . 
     When a high-level pulse signal (control signal) S 1  is received from the control signal output unit  30 , the flash lamp  19  outputs excitation light. The Nd:YAG doped in the rod  20  is excited by the excitation light pumped by the flash lamp  19 . The Nd:YAG emits light when it changes from an excited state to a ground state. The light emitted from the rod  20  is amplified between the reflection mirror M 1  and the reflection mirror M 2 , and the Nd:YAG in the excited state performs stimulated emission. 
     The switch device  21  is an electro-optical crystal. When a voltage is applied to the switch device  21 , the switch device  21  becomes highly transparent to laser light (1064 nm). In other words, the switch device  21  is transparent to laser light when a voltage is applied thereto, but the switch device  21  is opaque to laser light when no voltage is applied thereto. In this case, while the pulse signal (control signal) S 3  given by the control signal output unit  30  is at a high level, the switch device  21  becomes highly transparent to laser light. By controlling the switch device  21 , the laser oscillator  1  outputs laser light (fundamental light or fundamental wave) having a predetermined pulse width. 
     The wavelength converter  2  uses an optical crystal to convert the wavelength of the laser light emitted from the laser oscillator  1 . More specifically, the wavelength is converted from 355 nm into 1120 nm. 
     The reflection mirror RM disposed between the wavelength converter  2  and the attenuation filter  3  reflects the laser light output from the wavelength converter  2  so that the laser light proceeds toward the attenuation filter  3 . 
     The attenuation filter  3  is a member for adjusting the intensity of the laser light. The pentacene FET  50 , i.e., an object to be observed, is an organic device. Accordingly, the attenuation filter  3  attenuates the intensity of the laser light so as to prevent the pentacene layer  8  from being physically destroyed by the laser light emitted thereupon. 
     The polarizer  4  passes only laser light having an oscillation in a predetermined direction. In other words, the polarizer  4  improves the quality of polarization component of the laser light emitted onto the pentacene FET  50 . The low pass filter  5  passes only light having a predetermined wavelength or more (having a predetermined frequency or less). In other words, in this case, light having a wavelength of 1120 nm passes through the low pass filter  5 , but the low pass filter  5  blocks light having a wavelength of 710 nm or less. The half mirror HM 1  provided between the low pass filter  5  and the objective lens OL reflects 50% of the laser light having passed through the low pass filter  5 , so that the reflected laser light proceeds toward the objective lens OL. The objective lens OL condenses the laser light transmitted from the laser oscillator  1  to a predetermined position of the pentacene FET  50 . At the same time, the objective lens OL passes 50% of the second harmonic emitted from the pentacene FET  50 . 
     The half mirror HM 2  outputs 50% of the light having passed through the half mirror HM 1  to the band-pass filter  12 . The half mirror HM 2  outputs the remaining 50% of the light having passed through the half mirror HM 1  to the image capturing device  18 . 
     The band-pass filter  12  blocks light having a wavelength of 800 nm or more. The band-pass filter  12  blocks the laser light reflected by the pentacene FET  50 , so that the reflected laser light (wavelength: 1120 nm) is not input into the photomultiplier tube  15 . 
     The polarizer  13  passes only the second harmonic having an oscillation in a predetermined direction. In other words, the polarizer  13  improves the quality of polarization of the second harmonic input into the photomultiplier tube  15 . The band-pass filter  14  is a filter for passing only the light in a band around the second harmonic (wavelength: 560 nm). 
     The photomultiplier tube  15  performs photoelectric conversion on the second harmonic incident to the photomultiplier tube  15 . Electric field distribution is detected based on this electric signal. 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     An object of the conventional invention is to find injection, accumulation, and transportation, i.e., some of dynamic characteristics of an organic device. Therefore, no attention has ever been given to generation and disappearance. For this reason, although an apparatus that can be applied to a horizontal structure device such as a pentacene FET has been suggested, no means for analyzing a vertical structure has ever been reported, and no means for improving the resolution thereof has ever been considered. 
     Since the conventional apparatus is not aimed at generation and disappearance of a carrier, the carrier is injected upon voltage application. Thereafter accumulation is obtained as an electric field distribution, and transportation is obtained as a time function. Therefore, the conventional apparatus has no excitation mechanism and no mechanism for obtaining change of a carrier over time in synchronization with excitation. 
     When the generation and the disappearance of carrier are taken into consideration as a problem to be solved, process of disappearance in materials having different molecular structures are naturally considered to rely on the materials, but there is no detection means for solving the problem. Moreover, in order to solve this problem, there is no output uniformizing means for solving the problem, i.e., the output of high-order harmonics of Nd:YAG laser output relies on wavelength. 
     An organic device is expected to be applied to, e.g., electroluminescence considered to be used for displays and illuminations, photoelectromotive force considered to be used for solar cells, and an FET serving as an organic semiconductor. In any of the devices, it is important to know a vertical structure. Originally, the first and second devices are vertical devices, and although the third device, i.e., the FET, has a horizontal structure in a channel, but has a vertical structure in an MIS structure controlling the channel. Therefore, it is important to find the vertical structure from the high-order harmonics in order to find injection, accumulation, transportation, generation, and disappearance, which are dynamic characteristics of an organic device. 
     Means for Solving the Problems 
     The present invention is made in view of the above viewpoints, and the present invention includes an emission unit for emitting a fundamental wave to an object to be observed, a detection unit for detecting the high-order harmonics generated according to an electric field distribution or a carrier distribution in the object when a voltage is applied to the object, and an excitation emission unit for emitting an excitation light for generating a carrier in the object, wherein a Z-axis polarizer passing an optical axis polarization component is provided between an objective lens and an emission unit for emitting the fundamental wave, wherein the present invention includes a control signal output unit  30  for outputting a second signal to cause the excitation emission unit to emit the fundamental wave to the object on the basis of a first signal of the excitation emission unit, and outputting a third signal to cause the detection unit to detect the high-order harmonics, and wherein the control signal output unit  30  is configured to change a time interval from when the first signal is output to when the second and third signals are output. Thus, the present invention provides means for evaluating generation and disappearance of the carrier. 
     The reason why the Z-axis polarizer is employed is as follows. The generation of the high-order harmonics at a position Z is given by the following expression. 
         P (2ω)=ε 0 χ (3)   E (0) E (ω) E (ω)  (1)
 
     In this case, E(ω) is an electric field of Z component of light, and E(0) is an electric field where the carrier is generated. 
     The output of the high-order harmonics from the entire organic film is given by the following expression. 
         I (2ω)∝|∫ 0   d   P   Z (2ω) dz|   2   (2)
 
     In other words, a detection apparatus for emitting fundamental light having an electric field in an optical axis direction and measuring the output of the generated high-order harmonics is required. 
     This is the point that is different from a conventional invention, i.e., a detection apparatus described in Japanese Patent Application Laid-Open No. 2008-218957. For this reason, it is essential to employ a polarizer for polarization in the optical axis direction (Z-axis polarizer). 
     There are three methods for forming the Z-axis polarizer. The configuration thereof is shown in  FIG. 2 . In order to make the Z-axis polarizer, a material basically having a polarization function is formed in a circular shape, and only the polarization of the Z-axis component is generated by setting off the polarizations of the X, Y axes components. Since there are several ways to do this, the configurations thereof are shown below. 
     In  FIG. 2A , the polarizer is formed using a photonic crystal, and polarization anisotropy is achieved by a deposition process in a longitudinal direction. When patterning process is set in a circular shape, the Z-axis polarization can be made. Thus, the Z-axis polarization can be easily achieved. However, there is a drawback in that an extinction ratio is highly dependent on a wavelength as shown in  FIG. 3 . Therefore, even if the characteristic of the extinction ratio is set at −20 dB, it is necessary to have a mechanism for replacing at least four filters in order to cover a wavelength area from 800 to 1200 nm to be analyzed. 
     The method as shown in  FIG. 2B  is a method using liquid crystals. The polarization characteristics of the liquid crystal depend on the molecular structure. In other words, the polarization characteristics are achieved by aligning the arrangement direction of the liquid crystals. Accordingly, the characteristic of the extinction ratio itself is inferior to that of the photonic crystal, but the dependency on the wavelength is low. Therefore, the liquid crystals are characterized in supporting all the wavelengths with one filter, and are suitable for the present invention. 
       FIG. 2C  is a Z-axis polarizer using a conical Brewster prism, in which functions are achieved by setting a conical angle at 68.4 degrees and forming a multi-layer film. In this case, however, it is difficult to position a conical prism. Like the photonic crystal, the wavelength dependency of the extinction ratio is high, which is not suitable for practical application. 
     Another method, i.e., a method for attaching Polarcors (TM) in a circular shape like a wooden mosaic work, may be considered. In this method, the wavelength decency of the extinction ratio is considered to be low, and therefore, this method is an effective method. In any case, the Z-axis polarizer is structured using any method, and an object of the present invention can be achieved. 
     Injection, accumulation, and transportation of charges can be observed and measured by measuring them using an organic FET by using parameters, i.e., a time interval between voltage application and fundamental light and an emission position in a lateral direction thereof. However, when generation and disappearance are measured, it is necessary to give an electric field perpendicular to a joint surface with fundamental wave, give excitation light for generating a carrier, and measure a time until excitation light disappears. 
     In other words, it is necessary to have an emission unit for giving a fundamental wave (fundamental light), provide a Z-axis polarizer between the emission unit and an objective lens to arrange a polarization plane in the Z-axis, and provide a mechanism between the objective lens and a detection unit for detecting the high-order harmonics so as to introduce excitation light. In addition, in order to easily measure the time, the excitation light requires a light source operating at a high speed, and unless setting is made outside of a detection wavelength area, a photomultiplier tube may be saturated, and the high-order harmonics may not be detected. Therefore, it is desired to set a wavelength in an absorbable range of an organic solar cell, an organic EL, and an organic semiconductor except for a detection wavelength range. For example, blue laser of 405 nm and red laser of 685 nm are suitable for this. When the above excitation light is used, the detection wavelength range from 420 to 600 nm is ensured, and a fundamental wave from 840 to 1200 nm can be supported. 
     Many of organic devices have properties similar to insulating materials, and most of them are designed to have a thicknesses of 1 μm or less so as to improve the conductivity. Therefore, the location accuracy in the Z axis direction is required to be about ±5 nm. A currently-available actuator achieving this is a piezo-actuator. The piezo-actuator has a movable range of as much as 100 μm, and when a heavy objective lens is driven, it is about 20 μm. Since this level of movable range affects operability, two-stage structure is employed to mount the piezo-actuator on the Z-stage, so that the operability and the resolution are ensured. 
     In this configuration, the Z-stage takes care of rough adjustment, and the piezo-actuator takes care of fine adjustment, so that this achieves a movable range of ±20 mm and a resolution of ±5 nm. 
     In order to obtain information about an interface at the joint portion, it is important to obtain information about generation and disappearance of carriers in a P-type material and an N-type material, and it is effective to make use of the fact that the high-order harmonics have characteristics intrinsic to materials. 
     To do so, it is effective for the detection apparatus to have a function for detecting this intrinsic wavelength. This function sweeps the wavelength of the fundamental wave generated by the emission unit, measures the intensity of high-order harmonics generated, and determine the wavelength at the peak value. However, this operation has three problems. The first problem is that a refractive index of glass used for the lens has wavelength dependency. Accordingly, it is necessary to correct the focal points of two groups of lenses, i.e., a waveform modifying unit and an objective lens. Another problem is that the output of the laser generating the fundamental wave has wavelength dependency, and is based on wavelength dependency of an AR coat of the used objective lens. 
     The following measures are taken to solve the former. As shown in  FIG. 4 , a waveform modifying unit  52  includes an iris diaphragm  25 , an attenuation filter  3 , a rotation control plate  26 , a convex lens  37 , a concave lens  38 , and an X-stage  31 . The iris diaphragm  25  modifies the beam of the fundamental wave, and the convex lens  37  and the concave lens  38  are used to control the diameter of the beam incident upon the objective lens OL. Therefore, when the fundamental wave is changed, the focal points of the convex lens  37  and the concave lens  38  change. This correction is performed as follows. 
     An image capturing device  18  is provided in order to adjust the optical axis of the Z-axis polarizer. As shown in  FIG. 4 , this configuration includes a slide-type reflection mirror RM′, an attenuation filter  3 , a polarizer  4 , and an image capturing device  18 . The beam outputted from the waveform modifying unit  52  may be adjusted so that collimated light is emitted as much as possible. Therefore, when a control unit  24  drives an actuator  23  attached to a wavelength converter  2  to change a fundamental wave, the position of the concave lens  38  mounted on the X-stage  31  is moved, and the beam waveform is observed. The wavelength and the position of the X-stage  31  are stored when the beam waveform is the sharpest, and the position of the actuator  23  and the position of the X-stage  31  are moved in a synchronized manner. Thus, this problem is solved. 
     The focal point of the objective lens is corrected as follows. Since the lens to be used has a field of vision of 0.22 mm, a detector having a smaller light-receiving diameter than this is provided at a sample position. The wavelength and the position of the piezo-actuator  29  for making the maximum output of the detector are obtained. The result thereof is stored, and the actuator  23  is moved in a synchronized manner. Thus, the problem is solved. 
     The correction of the high-order harmonics involves two factors. The first factor is uniformization of the intensity of the incident fundamental wave, and the other factor is correction of the output of the high-order harmonics. These are considered from the generation mechanism, and since they cannot be performed at a time, they are considered while they are divided into two. 
     The first factor is uniformization of incident side. As shown in  FIG. 5 , the output of the wavelength converter  2  changes about twice in a wavelength range from 800 to 1200 nm. Furthermore, the wavelength characteristic of the attenuation filter and the wavelength characteristic of the AR coat of the objective lens are added. This correction is performed as follows. The detector is placed at the sample position, and the rotation control plate  26  is driven based on the measurement value thus obtained. The uniformization is achieved by selecting the attenuation filter  3  so as to uniformize the intensity in a wavelength range from 800 to 1200 nm as much as possible. 
     The characteristics of the light receiving side result from the characteristic of the AR coat of the objective lens OL and the characteristic of the band-pass filters  14 ,  14 ′. The characteristics are corrected by measuring the wavelength dependency and storing relationship between the result and the wavelength. 
     The dimension of the vertical structure of the organic device is very thin, i.e., 1 μm or less, as described above. Accordingly, it is impossible to identify the interface surface thereof by using a measuring instrument. In the system according to the present invention, only the piezo-actuator ensures the accuracy. Therefore, it is the only possible method to identify the interface surface by using the output of the high-order harmonics of the piezo-actuator and the wavelength characteristic intrinsic to a material. 
     The intrinsic wavelength can be identified by the above method. Therefore, when the piezo-actuator  29  is driven while the Z-stage  39  is fixed, the high-order harmonics of respective materials are generated according to the positions of the materials as shown in  FIG. 6 . Accordingly, the data are normalized with the peak value of each of them being 1. When relationship between the position and the intensity is obtained, an intersecting point of the normalized intensities is a position corresponding to the interface. 
     There are three factors for improving the resolution in the optical axis (Z axis) direction. The first factor is that the SHG is output in proportional to a square of the intensity of the electric field. Therefore, since the SHG output is generated according to square-law characteristic with respect to the intensity of the light formed by the lens, the resolution improves in the optical axis direction. 
     Another factor results from the use of the Z-axis polarizer.  FIG. 8  is illustrates relationship between an numerical aperture (NA) and a Z-axis component of polarization.  FIG. 8  indicates that a smaller NA makes a smaller Z-axis component of polarization. This is because, when the beam is not condensed, X, Y axes components are not sufficiently set off. When this idea is applied to the spatial distribution of the intensity of the fundamental wave in the space, it is understood that the polarized component increases at the point where the light is condensed but the polarized component decreases at a point away from the point where the light is condensed, which suppresses the conversion into the SHG light. The above relationship is shown in  FIG. 7 . 
     The resolution in the Z-axis direction can be improved by increasing the apparent NA. This can be achieved by covering the center of the beam with slits and the like. In other words, instead of the iris diaphragm  25  of the waveform modifying unit, donut-shaped slits are provided as shown in  FIG. 9 . 
     In order to improve the resolution in the Z-axis direction, it is necessary to design the objective lens used for emitting light onto the object to be observed such that the objective lens has a low aberration with respect to the fundamental wave. In order to improve the sensitivity of detection of the SHG light, the design area of the AR coat needs to be in a range from 400 to 600 nm. Since it is impossible, in terms of optics, for the AR coat to cover the range from 400 to 1200 nm, priority is given to the area from 400 to 600 nm. In this case, although the transmittance characteristic in the range from 800 to 1200 nm is sacrificed, the output of the laser of the fundamental wave emission unit is high, i.e., it is at such a high level that the output is attenuated by the attenuation filter. Therefore, the reduction of the transmittance caused by the AR coat can be sufficiently covered. 
     This apparatus measures the lifetime as follows. The excitation light for generating the carrier is emitted onto the object to be observed, so that the carrier is generated. Then, the organic material is distorted by the electric field generated by the carrier, and a non-linear component is generated. Even after the excitation light is cut off, the non-linear component is held as long as the carrier does not disappear. Therefore, the fundamental wave is emitted onto the object to be observed, and SHG light generated therefrom is detected, whereby the measurement is performed. Therefore, when this operation is performed with respect to a temporal axis, the disappearance process of the carrier can be measured, based on which the lifetime can be measured. 
     For example, when the object to be observed is a solar cell, it is constituted by, for example, a P-type material, i.e., pentacene, and an N-type material, C60. Since they make hetero junction, the hole disappearance process and the electron disappearance process are different from each other. The detection means using the SHG light selects a fundamental wave to find an electric field intrinsic to a material. Therefore, the disappearance process for each carrier can be found. In other words, the lifetimes of each of the electron and the hole can be measured by measuring the lifetime intrinsic to each wavelength. 
     According to the present invention, injection, accumulation, transportation, generation, and disappearance, i.e., dynamic characteristics of an organic device, can be found in terms of lifetime, and difference of disappearance processes using difference of materials can be found. This provides means for considering the method for reviewing improvement means of an interface from various perspectives of materials, structures, and processes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a figure illustrating an example of configuration of a detection apparatus according to the present invention; 
         FIGS. 2A to 2C  is a figure illustrating three methods for forming a Z-axis polarizer according to the present invention, wherein  FIG. 2A  is a method using a photonic crystal,  FIG. 2B  is a method using a liquid crystal, and  FIG. 2C  is a method using a conical Brewster prism; 
         FIG. 3  is a figure illustrating an extinction ratio characteristics of a Z-axis polarizer using a photonic crystal; 
         FIG. 4  is a figure illustrating an example of configuration of a waveform modifying unit according to the present invention; 
         FIG. 5  is a figure illustrating output characteristics of the wavelength converter according to the present invention; 
         FIG. 6  is a figure illustrating a method for identifying a position of an interface according to the present invention; 
         FIG. 7  is an explanatory drawing of a Z-axis resolution according to the present invention; 
         FIG. 8  is a figure illustrating relationship between an NA and a Z-axis component of polarization according to the present invention; 
         FIG. 9  is a figure illustrating a slit pattern according to the present invention; 
         FIG. 10  is a figure illustrating an example of configuration of a waveform modifying unit according to the present invention; 
         FIGS. 11A to 11C  are figures illustrating a Z-axis polarization unit according to the present invention, wherein  FIG. 11A  is a figure illustrating a configuration of the Z-axis polarization unit,  FIG. 11B  is a figure illustrating a cross section of a beam when there is no polarizer, and  FIG. 11C  is a figure illustrating a cross section of beam after the beam has passed through the polarizer; 
         FIG. 12  is a figure illustrating an example of configuration of a detection unit according to the present invention; 
         FIG. 13  is a figure illustrating an example of specification of a filter according to the present invention; 
         FIG. 14  is a figure illustrating timing of operation of a processing unit according to the present invention; 
         FIG. 15  is a figure illustrating wavelength sweeping according to the present invention; 
         FIG. 16  is a figure illustrating square-law characteristic of SHG light at an intrinsic wavelength; 
         FIG. 17  is a figure illustrating a configuration of a conventional detection apparatus; and 
         FIG. 18  is a figure illustrating a conventional TOF method. 
     
    
    
     PREFERRED EMBODIMENT OF THE INVENTION 
     As shown in  FIG. 1 , an SHG intensity distribution obtaining apparatus  100  includes a laser oscillator (light source)  1 , a wavelength converter  2 , a waveform modifying unit  52 , a reflection mirror RM, an attenuation filter  3 , a polarizer  4 , a Z-axis polarization unit  53 , a low pass filter  5 , a slide-type reflection mirror RM′, an objective lens OL, and an excitation light source (excitation emission unit)  36 . In addition, the SHG intensity distribution obtaining apparatus  100  includes a stage (not shown) on which an organic solar cell (object to be observed) is placed. In addition, the SHG intensity distribution obtaining apparatus  100  includes a slide-type reflection mirror RM′, band-pass filters  14 ,  14 ′, and a photomultiplier tube  15 . In addition, the SHG intensity distribution obtaining apparatus  100  includes a lens  17  and an image capturing device  18 . In addition, the SHG intensity distribution obtaining apparatus  100  includes a control signal output unit  30 . 
     In the SHG intensity distribution obtaining apparatus  100 , in an electric field induced based on carriers accumulated in an organic solar cell by excitation light, laser light (fundamental wave) which is excited by the laser oscillator  1  and whose wavelength is converted by the wavelength converter  2  is emitted onto the organic solar cell, and the second harmonic generated by the organic solar cell is detected by the photomultiplier tube  15 . The processing unit  16  performs ON/OFF control of the excitation light source  36  with a pulse signal S 1 , and thereafter, controls a time when a pulse signal S 3  is output to the switch device  21 , controls a time when the gate of the photomultiplier tube  15  is controlled with a pulse signal S 4 , and controls an integrator  34  with a pulse signal S 5 , thus controlling a time when data are sampled. With this, a change of carriers induced by the excitation light source  36  over time within the organic solar cell after shut off of the excitation light source  36  can be found by varying a time interval of a pair of pulse signals S 3 , S 4 , S 5  and the pulse signal S 1 . When the SHG intensity distribution obtaining apparatus  100  is used to accurately change the position in an optical axis direction of the organic solar cell, relationship between an SHG output intensity and a decay time thereof corresponding to the electric field based on the accumulation of carriers in the organic solar cell can be derived. 
     The laser oscillator  1  includes a flash lamp (excitation light source)  19 , a rod  20 , a switch device (switch unit)  21 , reflection mirrors M 1 , M 2 , THG (Third Harmonic Generation) crystal  22 . The laser oscillator  1  is a so-called solid laser device operating in Q-switch mode. The laser oscillator  1  outputs laser light having a predetermined pulse width (fundamental light or fundamental wave). The laser oscillator  1  outputs laser light having a wavelength of 355 nm. The laser oscillator  1  serves not only as a light source but also as an emission unit. 
     The flash lamp  19  is an excitation light source for pumping. The rod  20  is a material doped with Nd:YAG (laser medium). The reflection mirror M 1  is provided at one side of the rod  20 . The reflection mirror M 2  is provided at the other side of the rod  20 . An oscillator is constituted by the rod  20  and the reflection mirrors M 1 , M 2 . The switch device  21  is provided between the rod  20  and the reflection mirror M 1 . 
     When a high-level pulse signal (control signal) S 2  is received from the control signal output unit  30 , the flash lamp  19  outputs an excitation light. The Nd:YAG doped in the rod  20  is made into excitation light by the excitation light pumped by the flash lamp  19 . The Nd:YAG emits light when it changes from an excited state to a ground state. The light emitted from the rod  20  is amplified between the reflection mirror M 1  and the reflection mirror M 2 , and the Nd:YAG in the excited state performs stimulated emission. 
     The switch device  21  is an electro-optical crystal. After a voltage is applied to the switch device  21 , the switch device  21  becomes highly transparent to laser light (1064 nm). In other words, the switch device  21  is transparent to laser light when a voltage is applied thereto, but the switch device  21  is opaque to laser light when no voltage is applied thereto. In this case, while the pulse signal (control signal) S 3  given by the control signal output unit  30  is at a high level, the switch device  21  becomes highly transparent to laser light. By controlling the switch device  21 , the laser oscillator  1  outputs laser light having a predetermined pulse width (fundamental light or fundamental wave). 
     The wavelength converter  2  uses an optical crystal to convert the wavelength of the laser light emitted from the laser oscillator  1 . More specifically, the wavelength is converted from 355 nm into 800-1120 nm. 
     The attenuation filter  3  is a member for adjusting the intensity of the laser light. An organic solar cell, i.e., an object to be observed, is an organic material. Accordingly, the attenuation filter  3  attenuates the intensity of the laser light so as to prevent the organic solar cell from being physically destroyed by the laser light emitted thereupon. 
       FIG. 10  illustrates a configuration of the waveform modifying unit  52 . The light output from a wavelength conversion unit  2  has a collimated beam shape having a diameter of about 5 mm. Accordingly, the light is controlled by an iris diaphragm  25  to have a diameter of 5 mm, and the light passes through the attenuation filter  3  and the attenuation filter  3  attached to a rotation control plate  26 . Then, the beam diameter of the light is controlled by a convex lens  37 , and the light is made into a collimated beam by the concave lens  38 . Thus, the light is transmitted according to an aperture of an objective lens OL. 
     The sweeping range of the fundamental wave is 800 nm to 1200 nm. Accordingly, the focal points of lenses  37 ,  38  change. In order to correct this, the concave lens  38  is mounted on an X-stage  31 , and the position thereof is driven in synchronization with the wavelength of the fundamental wave, so that the focal points are corrected. 
       FIGS. 11A to 11C  illustrates a Z-axis polarization unit  53  including a Z-axis polarizer  27  and an adjustment system thereof. Due to the principle of a Z-axis polarization, the Z-axis polarization is to set off and extract X, Y polarizations, and therefore, it is necessary to make the beam position and the position of the Z-axis polarizer be the same. This operation is performed with the configuration as shown in  FIG. 11A . The light having passed through the Z-axis polarizer  27  is reflected by a slide-type reflection mirror RM′, and the light passes through the attenuation filter  3  and the polarizer  4 . Then, the light is guided to the image capturing device  18 . The light that has not passed through the polarizer  4  has a circular beam shape as shown in  FIG. 11B . However, the light having passed through the polarizer  4  has a butterfly shape as shown in  FIG. 11C . The XY stage  28  is moved and adjusted so as to make this shape symmetrical. 
     The adjustment system as shown in  FIGS. 11A to 11C  is also used to correct the focal point in the modifying of the waveform as described above. In this case,  FIG. 11B  is obtained. Accordingly, the X-stage  31  is driven so as to adjust the position at which this beam becomes in the sharpest focus, and this position is memorized. The focal point is corrected by synchronizing the wavelength of the fundamental wave and the memorized position of the X-stage  31 . After the above correction is made, the slide-type reflection mirror RM′ is moved, so as to pass the beam. 
       FIG. 12  illustrates an example of configuration of the detection unit. The fundamental wave having a wavelength of 800 to 1200 nm passes through the low pass filter  5  and a Dichroic mirror  35 , passes through a bellows, and enters into the objective lens OL. The bellows ensures a movable range of the objective lens OL, and fixes the detection unit. 
     The SHG light is reflected by the Dichroic mirror  35 . The SHG light passes through two kinds of band-pass filters  14 ,  14 ′, and the SHG light is guided to the photomultiplier tube  15 . The excitation light having a wavelength of 405 nm passes through a collimator lens  17 , and is reflected by the band-pass filter  14 ′. The excitation light is reflected by the Dichroic mirror  35 , and is incident upon the objective lens OL. 
     The light reflected by the slide-type reflection mirror RM′ is observed with the image capturing device  18 . White light is incident from a slide half mirror (not shown). 
       FIG. 13  illustrates an example of specification of a filter. The low pass filter  5  has a transmittance of 1×10 −6  or less in a range of 400 to 600 nm. When the light is reflected by the Dichroic mirror  35 , the transmittance is 1×10 −8  or less, which hardly affects the detection unit. The Dichroic mirror  35  has a transmittance of 95% or more in a range of 760 to 1200 nm, and has a reflection rate of 98% or more in a range of 420 to 660 nm. The excitation light having a wavelength of 405 nm is used in this design. Alternatively, a light source of 680 nm may be used when the filter configuration is changed. The purpose of the band-pass filter  14  is to passes the SHG light of 420 to 600 nm and blocks the fundamental light of 800 to 1200 nm. When the laser power is assumed to be 500 mW, the band-pass filter  14  has a performance of blocking the fundamental light in a level of 0.3 nW. The excitation light uses laser light of 405 nm, and the output thereof is set at about 3 mW. In this case, the output of the photomultiplier tube is 0.5 nW or less. In this configuration, the transmittance of the SHG light is 80% or more in a range of 420 nm to 600 nm except for 75% in a range of 420 nm to 425 nm. 
     The accurate position control of the objective lens OL is achieved with a combination of a Z-stage  39  and a piezo-stage (an embodiment of piezo-actuator)  29 . Automatic Z-stage ZA07A-X1-R made by Kohzu Precision Co., Ltd. is used as the Z-stage. Regarding the accuracy, the automatic Z-stage ZA07A-X1-R has a minimum resolution of 0.25 μm and a movable range of ±10 mm. The piezo-stage is dedicated for the objective lens. The piezo-stage has a movable range of about 20 μm and a resolution of ±5 nm. With this combination, the required resolution is ensured. 
     The waveform is modified with the configuration as shown in  FIG. 10 . The light output from the wavelength conversion unit  2  enters into the iris diaphragm  25 . The dimension of the iris diaphragm  25  can be changed from 1 to 10 mm. It is manually set at 5 mm. Thereafter, the output is attenuated by the attenuation filter  3 . The attenuation filter  3  attached to the rotation control plate  26  is rotated, and the output emitted from the objective lens OL is uniformized. With the combination of the convex lens  37  and the concave lens  38 , the controlled beam is made into a beam suitable for the aperture diameter 3.0 mm of the objective lens OL. 
     When the wavelength of the incident light changes in a range of 800 to 1200 nm, the focal points of the convex lens  37  and the concave lens  38  change, which no longer outputs collimated light. In order to correct this, the concave lens  38  is mounted on the X-stage  31 . According to the above method, a corrected position is detected. The focal lengths are corrected by synchronizing the corrected position and the actuator  23  attached to the wavelength converter  2 . 
     The focal point of the objective lens OL is corrected as follows. The waveform modifying unit corrects the focal point, and the correction is executed. Thereafter, collimated light is emitted into the objective lens OL. A detector (not shown) having a small light-receiving diameter (28 μmφ) is placed under the objective lens OL. First, a maximum output is detected when the wavelength is 800 nm. The objective lens OL is a 100× lens, which has a vision range of 0.22 mm. Accordingly, the position of the focal point of the objective lens OL can be sufficiently detected. Thereafter, the piezo-stage  29  is driven. Every time the wavelength is changed, a changed peak position is detected. Relationship between the values and the wavelengths is made into a table, so as to allow correction of the position. 
     A material used for an organic device generates SHG light intrinsic to the material. Therefore, when the fundamental wave is incident according to the wavelength of the intrinsic SHG light generated, the SHG light can be generated with an accuracy of 1 nm, i.e., the resolution of the laser oscillator  1 . When the laser oscillator  1  has this resolution, the material can be sufficiently distinguished from another material. Therefore, this apparatus is arranged with a function for identifying the intrinsic SHG light. 
     The measurement result at C60 is shown in  FIG. 16 . The fundamental wave is swept between 800 and 1200 nm to measure the SHG light. The intrinsic wavelength can be determined from the wavelength dependency. Whether the obtained intrinsic wavelength is of SHG light or not can be verified as follows. The rotation control plate  26  is driven, and the output of the fundamental wave is changed for the intrinsic wavelength. Then, since the SHG light has characteristics of the above expression (2), it is proportional to a square of the output. The obtained intrinsic wavelength can be determined to be of SHG light by checking this. 
     When the intrinsic wavelength of each material can be identified as described above, the position of the interface of the organic device can be identified using the wavelength. First, the focus is positioned onto the surface of the sample of the image capturing device  18  and the objective lens OL. Since design values of the organic device are already known, the SHG light having the intrinsic wavelength can be detected in this configuration as follows. The system is switched to a detection system, and thereafter, the position of the objective lens OL is set at a lower surface using the piezo-stage  29 , and is gradually moved to an upper surface. Thus, the SHG light having the intrinsic wavelength can be detected. In a case of PN junction, this operation is repeated twice, and outputs of an N-side intrinsic wavelength and a P-side intrinsic wavelength are detected. Thereafter, normalization is performed with peak outputs thereof being 1. A point where the output results (curves) intersect with each other is a position of the interface (see  FIG. 6 ). 
     According to the above method, information including many interfaces can be obtained using the intrinsic wavelength and the piezo-stage  29 . 
     In order to improve the resolution of this apparatus in the optical axis direction, the focal depth is reduced. In other words, the focal distance is reduced, and the NA is increased. However, due to the limitation of the dimension of the sample, the NA cannot be increased blindly. Where a cover glass for the sample has a thickness of 0.5 mm, and the device has a thickness of 0.2 to 0.3 mm, a space of at least 0.2 mm is needed. Therefore, about 1.0 mm is needed as the focal depth. In this focal depth, the NA is limited to 0.9 or less. 
     There are three factors for determining the resolution of this apparatus in the optical axis direction. The first factor is detection of the SHG light. As can be seen from the expression (2), the output is proportional to a square of the intensity of the light. Therefore, when the intensity of the light attenuates 0.7, the output of the SHG light becomes 0.5, which improves the resolution. 
     Another factor is the intensity of the electric field applied to the sample as can be seen from the expression (1). In other words, it is dependent upon the intensity of the electric field generated by the Z-axis polarizer. This intensity is dependent upon the NA as shown in  FIG. 8 . This calculated value represents the intensity of the light at the focusing position. Therefore, even with the same NA, displacement from the focal point results in the same effect as that caused by decrease of the NA. This means that, at a position displaced from the focal point, the electric field is weaker in the optical axis direction, which reduces the intensity of the SHG light. As a result of this effect, the resolution is improved. 
     The third factor is a method for reducing an apparent focal depth. More specifically, in this method, a central portion of the laser light output from the wavelength converter  2  is covered with slits, and the donut-shaped light having passed through the slits is condensed, so that the focal depth is reduced. This method also improves the resolution. The three methods as described above are used to improve the resolution. 
     In order to improve the resolution in this method, it is understood that the condensing characteristics of the fundamental light is important. The condensing characteristics of the lens are determined by aberration, but the aberration has a wavelength dependency. Therefore, it is important to choose in which wavelength range the aberration of the lens is designed. Currently-available microscopes include a microscope for a visible light range and a microscope suitable for infrared light. In this apparatus, it is necessary to decrease the aberration of the fundamental wave, but it is necessary to increase the transmittance of the visible light as much as possible. This is to improve the sensitivity of the SHG light. 
     In an ideal case, the AR coat is required to have a high transparency in the entire area from 400 to 1200 nm. However, in terms of optics, such high performance is impossible. Therefore, it is required to design the lens in which the AR coat is adjusted for 400 to 600 nm and the aberration is adjusted for 800 to 1200 nm. 
     The following procedure is needed to measure a lifetime. First, the surface of the object to be observed is observed with the image capturing device  18 , and the focal point of the objective lens OL is set at the surface of the object to be observed. Subsequently, the focal point of objective lens OL is lowered to the position where the organic material is present, and the fundamental wave is swept to respectively identify the intrinsic wavelengths. After the intrinsic wavelengths are identified, the intrinsic wavelengths are used to sweep the position of the piezo-stage  29 , thereby identifying the position of the interface. After the position of the interface is identified, the objective lens OL is moved to the position calculated from the design value. Then, using the intrinsic wavelengths, a time of the SHG light is measured. Control signals are classified into two groups. They are a signal S 1  for controlling the excitation light, signals S 2 , S 3  for controlling laser lights, and signals S 4 , S 5  for respectively controlling the photomultiplier tube and the integrator. The signals S 2 , S 3 , S 4 , S 5  are controlled together. 
     After the Q switch is driven, a trigger signal is input to the laser oscillator  1 . Then, after a certain period of time passes since the trigger signal, the laser oscillator  1  starts laser oscillation. This period of time is intrinsic to the apparatus. When 245 μs passes since the signal S 2  is turned on, accumulation occurs. When 4.38 μs passes since then, a trigger signal is transmitted. When 100 ns passes since the trigger signal, laser oscillation starts. When 215 ns passes since a gate trigger of the gate-attached photomultiplier tube  15  is turned ON, the photomultiplier tube  15  attains the maximum detection sensitivity. Since, the pulse width of the laser light is several nanoseconds, it is impossible to obtain data unless the detection is made according to this timing. On the other hand, it takes 5 ns to drive the integrator  34 . Therefore, times from when the laser is driven to when integration starts is as follows. As shown in  FIG. 14 , while the signals S 2 , S 3 , S 4 , S 5  are synchronized, the above relationship is maintained, and the measurement is performed with the excitation light n times with an interval of m [ns]. Based on the result thereof, a decay time constant is measured, whereby the lifetime can be measured. 
     The lifetimes of electrons and holes can be measured by measuring the SHG lights intrinsic to different materials. Since hetero junction is formed, and materials are different, it is considered that the interface densities are different. Therefore, carrier disappearance is considered to be different between the electrons and holes, and the data thereof are considered to provide important information when the band states of organic devices are studied. 
     Embodiment 
     A detection apparatus  100  as shown in  FIG. 1  is structured. OPO excitation pulse YAG laser made by Continuum, Inc. and an optical parametric oscillator are employed as the laser oscillator  1  and the wavelength converter  2 . A manual actuator is detached so as to automatically change the wavelength, and an automatic actuator  23  and a control unit  24  are attached. In this configuration, the wavelength of the fundamental wave can be automatically changed. 
     An iris diaphragm  25  is attached to a waveform modifying unit  52 . Seven types of attenuation filters  3  are attached to a rotation control plate  26 , so that the attenuation can be controlled in eight levels. Using the above attenuation filters  3  and the fixed attenuation filter  3 , the attenuation can be controlled automatically. The output thereof passes through a convex lens  37  and a concave lens  38 , so that the beam diameter is adjusted for an aperture diameter of an objective lens OL, i.e., 3 mm. The concave lens  38  is mounted on the X-stage  31 , and the position of the concave lens  38  is automatically moved, so that the position of the focal point can be corrected. 
     The light having passed through the waveform modifying unit  52  enters into a Z-axis polarizer  27  via a reflection mirror RM. The position of the Z-axis polarizer  27  is determined as follows. An XY stage  28  is driven, and the light is reflected by a slide-type reflection mirror RM′, and is guided to an image capturing device  18  via an attenuation filter  3  and a polarizer  4 . The position of the Z-axis polarizer  27  is adjusted so that a butterfly shape becomes symmetrical as shown in  FIG. 11C . Thereafter, the slide-type reflection mirror RM′ is driven, so that the light enters into the objective lens OL via a Dichroic mirror  35 . As a result, the fundamental wave is emitted onto the object to be observed. 
     The NA of the objective lens OL is 0.9, and the working distance is 1.0 mm. A correction tube is attached to the lens, so as to correct the refractive index of the cover glass. 
     The objective lens OL is mounted on a piezo-stage  29 , and the piezo-stage  29  has a movable range of 20 μm and a resolution of 5 nm. The piezo-stage  29  is mounted on a Z-stage  39 , and the Z-stage  39  has a movable range of 20 mm and a resolution of 0.5 μm. This movable portion and the detection unit are coupled via a bellows (not shown), and are shielded from any external light. 
     The SHG light generated by the fundamental wave is condensed by the objective lens OL, and is reflected by the Dichroic mirror  35 . Then, the SHG light is guided to the detection unit. In the detection unit, the SHG light passes through a band-pass filter  14  and a band-pass filter  14 ′ inclined 45 degrees, and passes through the slide-type reflection mirror RM′. Then, the SHG light is guided to a photomultiplier tube  15 , and is transmitted to an integrator  34  via an amplifier (not shown). The integrator  34  outputs it as data. 
     The intrinsic wavelength is identified as follows. First, the wavelength is swept to obtain SHG light. Subsequently, the rotation control plate  26  is driven at the wavelength, and a determination is made as to whether the SHG light has square-law characteristic or not by changing the output of the fundamental wave. When the SHG light is determined to have the square-law characteristic, it is adopted as the intrinsic wavelength.  FIG. 15  illustrates an example of the intrinsic wavelength. The data are of C60, and are at 500 nm. In a case of pentacene, data are present at a position of 430 nm. Dynamic characteristics of the organic device in a particular area can be obtained by using the intrinsic wavelength. 
     Subsequently, a method for identifying an interface will be explained using an example of an organic solar cell. In the measurement example, C60 of 100 nm, pentacene of 100 nm, and ITO attached cover glass of 500 μm are provided on an electrode substrate. First, the sample is set on the apparatus, and while light source  32  is emitted, the Z-stage  39  is driven. The surface of the solar cell is observed with the image capturing device  18 . The Z-stage  39  is stopped when the focus is obtained. Subsequently, since the thickness of the cover glass is 500 μm, the Z-stage  39  is lowered, and the correction tube is moved, so that the focus is obtained there. 
     Subsequently, the objective lens OL is lowered 2 μm with the piezo-stage. A fundamental wave of 1000 nm is output from there, and while the output of C60 is measured, the objective lens OL is moved upward 3 μm. Subsequently, it is lowered 3 μm again. This time, a fundamental wave of 860 nm is output, and the objective lens OL is moved upward 3 μm. Then, the same measurement is performed. Subsequently, each piece of data is normalized, and the position of the interface is identified based on the intersecting point. The thickness of C60 identified with the above operation was 110 nm. 
     The measurement procedure of the lifetime is performed as follows. 
     The control signal output unit  30  outputs the following signal. A start signal is output from a signal S 1  to turn ON excitation light. The signal is cut off in 249.47 μs. A signal S 2  is triggered at the rise of S 1  signal. 245 μs later, it is ready to receive a gate signal. A signal S 3  is triggered 249.38 μs later. Accordingly, 100 ns later, a fundamental wave is output. This means that the fundamental wave is output after 10 ns since the excitation light is cut off. Regarding the gate signal of the photomultiplier tube  15 , S 4  is output at a position of 215 ns before output of the fundamental wave. Before the above, at 10 ns, a signal S 5  for driving an integrator is output, so that SHG light is retrieved. In a subsequent step, the steps S 2 , S 3 , S 4 , S 5  are delayed 10 ns with respect to the signal S 1 . This is performed successively until a time when the output becomes the same as the non-excited state. It is to be understood that the configured time, 10 ns, can be changed and set in a range from about 10 ns to about 10 ms. 
     In the above configuration, the apparatus was driven, and the solar cell including pentacene and C60 was measured. 4×10 −4  sec was obtained as the lifetime of the pentacene. 1.0×10 −3  sec was obtained as the lifetime of the C60. These values have not hitherto been measured, and we have to further study the reliability of these values. In any case, we have found that this apparatus can measure these parameters. 
     The present invention relates to an apparatus capable of detecting injection, accumulation, transport, generation, and disappearance processes of carrier, i.e., dynamic characteristics of organic semiconductors. Accordingly, the present invention can be applied to electroluminescence, photoelectromotive force, carrier transport devices, and in particular, to analysis of generation and disappearance processes. Therefore, the present invention can be applied to a wide range of subjects such as analysis of lifetime of electroluminescence, analysis of photoelectric conversion efficiency of photoelectromotive force, findings about interface mobility of an organic semiconductor, and the like. 
     In particular, in order to improve the photoelectric conversion efficiency of a solar cell, it is necessary to start consideration from structures, materials, and processes. Although cut-and-try researches have hitherto been made, information obtained with this detection apparatus is expected to greatly contribute to the improvement.