JPS63304268A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve sensitivity for light of an electrophotographic sensitive body by providing internal amplifying function capable of amplifying a charge carrier generated by the absorption of electromagnetic wave in a photoconductive layer of an electrophotographic sensitive body, regulating thus the number of the carrier to be generated from a photon of the electromagnetic wave to >=1. CONSTITUTION:The electrophotographic sensitive body of this invention is constituted of a photoconductive layer 2 contg. a charge carrier amplifying layers 3 on a photoconductive base body 1, wherein each charge carrier amplifying layer 3 is constituted of >=2 semiconductor layers having 5Angstrom -1mu thickness and 10meV-5eV potential energy difference at the interface of jointing said semiconductor layers, and the quantum efficiency of said charge carrier amplifying layer 3 for the generation of charge carrier due to electromagnetic wave in a >=3X10<5>V/cm electric field impressed in reverse bias direction. Thus, the charge carrier generated by electromagnetic wave is amplified by allowing the charge carrier generated in a region for absorbing electromagnetic wave at the inside of the charge carrier amplifying layer 3 to cause electron avalanche in the inside of the charge carrier amplifying layer 3. By this constitution, the sensitivity of an electrophotographic sensitive body is increased.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a high-sensitivity electrophotographic photoreceptor.

BACKGROUND OF THE INVENTION Conventionally, attempts have been made to improve the photosensitivity of electrophotographic photoreceptors based on the mechanism of photoconductivity, from the viewpoints of light generation and transportation of photogenerating carriers.

The former attempts to improve sensitivity by expanding the usable wavelength range. For example, the sensitivity of selenium in the long wavelength range is limited by adding tellurium, which has a smaller optical bandgap. Furthermore, by adding germanium, the light absorption region of hydrogenated amorphous silicon is expanded to a long wavelength region, thereby increasing the sensitivity in the visible range, which is effective as an electrophotographic photoreceptor. In order to efficiently separate and generate charge carriers for photoconductivity using absorbed light, improvements were made such as reducing the number of recombination centers. or,
The latter aims to improve sensitivity by transporting the generated charge carriers to the opposing part without loss.
In particular, in a functionally separated photoreceptor, it is necessary to increase the transport capacity of the generated charge carriers and to efficiently inject the charge carriers generated in the charge generation layer into the charge transport layer. From this point of view, attention is paid to the reduction and removal of impurities and defects that may cause deep or shallow traps, and the values of band energy and ionization potential, which are closely related to charge carrier injection and transport ability, are taken into account. It is configured such that all charge carriers generated by light absorption are transported. In this way, the means for improving the photosensitivity of electrophotographic photoreceptors are to increase the amount of absorbed electromagnetic waves, to efficiently generate charge carriers from the absorbed electromagnetic waves, and to efficiently dissipate the generated charge carriers. Well-transported and limited.

Problems to be Solved by the Invention Therefore, the photosensitivity of a conventional electrophotographic photoreceptor is determined from the position of the absorbed photon by the principle that a pair of charge carriers can be generated by the absorption of one photon. It couldn't be more sensitive. In other words, the quantum efficiency of charge carrier generation never exceeded 1.

The present invention is based on a completely different idea from conventional ones,
By increasing the number of carriers generated from one photon of electromagnetic waves to one or more, the photosensitivity is increased, making it possible to create a highly sensitive electrophotographic photoreceptor that could not be achieved with conventional electrophotographic photoreceptors. The purpose is to provide.

Means for Solving the Problems The above object of the present invention is to provide a photoconductive layer of an electrophotographic photoreceptor,
This is achieved by providing an internal amplification function that amplifies the charge carriers generated by absorption of electromagnetic waves. As a result of various experimental studies conducted by the present inventor, it has been found that it is possible to provide an electrophotographic photoreceptor with the function of internally amplifying charge carriers generated by absorption of electromagnetic waves by causing an electron avalanche inside the photoconductive layer. We have obtained certain knowledge and have completed the present invention based on this knowledge.

The electrophotographic photoreceptor of the present invention is formed by forming a photoconductive layer including a charge carrier amplification layer on a conductive support, each of the charge carrier amplification layers having a thickness of 5 Å to 1 μm, and having a thickness of 5 Å to 1 μm at the bonding interface. It is composed of two or more semiconductor layers with a potential energy difference of 10IIlev to 5eV, and the quantum efficiency of charge carrier generation by electromagnetic waves is 1 or more under an electric field of 3X10"V/n or more applied with a reverse bias. It is characterized by

In this electrophotographic photoreceptor, the charge carriers generated by the electromagnetic waves are removed by causing an electron avalanche inside the charge carrier amplification layer. amplify,
Increase sensitivity.

The electrophotographic photoreceptor of the present invention has a structure as shown in FIG. It consists of a conductive substrate 1 and a photoconductive layer 2 provided thereon. Roughly speaking, the photoconductive layer 2 has p 1p, p-1r, n- for forming an avalanche generation region therein.
A charge carrier amplification layer having a layer structure formed by sequentially laminating one pair or two or more pairs of at least two semiconductor layers made of photoconductive materials selected from photoconductive materials having conductivity types of 1n and n type. 3 inside.

In the electrophotographic photoreceptor of the present invention, the photoconductive layer mainly contains x
It can also be divided into a charge carrier amplification layer, which corresponds to a so-called charge generation layer, which is involved in the generation and amplification of charge carriers by RA waves, and a charge transport layer, which transports charge carriers generated in this part. In general, a surface layer can be provided on the charge carrier amplification layer or the charge transport layer for the purpose of protecting them or reducing optical reflection. Further, a charge injection blocking layer may be provided between the conductive support and the photoconductive layer.

Each layer constituting the electrophotographic photoreceptor of the present invention will be explained below.

In the electrophotographic photoreceptor of the present invention, the substrate material includes:
Either a conductive material or an insulating material treated to make it conductive may be used, such as stainless steel, chromium, aluminum, titanium, etc. Insulating materials include, for example, polyimide, polyester, and polyester. Mention may be made of ether sulfones.

In the electrophotographic photoreceptor of the present invention, the charge carrier amplification layer is
p 1ps p-1i, n-1ns At least two layers of n-type semiconductor layers are sequentially laminated. This charge carrier amplification layer is made of hydrogenated amorphous silicon containing group I or V atoms as impurities to control the conduction type, germanium, tin, carbon to control the conduction type or the absorption amount and wavelength of electromagnetic waves. , hydrogenated amorphous silicon containing impurities such as nitrogen, oxygen, halogen, and aluminum, inorganic semiconductors such as selenium and zinc oxide, p-type pigments such as phthalocyanine, merocyanine, rose bengal, and squerium, malachite green, Piacia tool, rhodamine B, n such as triphenylmethane
It can be manufactured by selecting semiconductors having different conductivity types from among organic semiconductors typified by type dyes and stacking them to form at least one pair of semiconductor junctions. In this case, the conductor and/or
Or the potential energy difference in the valence band is 10IIl
It is necessary to select a semiconductor so that the voltage is between ev and 5 eV. Among these, hydrogenated amorphous silicon produced by the plasma CVD method is the most suitable semiconductor for the present invention in that thin films can be repeatedly formed while controlling the conductivity type.

In the charge carrier amplification layer of the present invention, in order to effectively utilize the charge carrier amplification function and cause an electron avalanche inside the layer, it is necessary to use the above two or three types of semiconductor layers having different conductivity types. A pair of layers may be formed, or a large number of pairs may be repeated to improve the photocurrent amplification factor of the entire photoconductive layer. In particular, when two or more pairs of semiconductor junctions are used, it is possible to suppress the increase in dark current and the breakdown phenomenon caused by the electron avalanche phenomenon starting from thermally excited charges other than the electron avalanche caused by charge carriers generated by electromagnetic waves. More favorable results are obtained.

In addition, the thickness of the charge carrier amplification layer on the side to which electromagnetic waves are irradiated is determined from 0.01 to 100IiIA1 depending on the absorption coefficient to sufficiently absorb the desired electromagnetic waves that exhibit the amplification effect.
Preferably, the thickness is appropriately set in the range of 0.1 to 20 #I, and the thickness of at least two types of semiconductor layers to be bonded is 5 Å each.
~1 μs, preferably 10 Å to 0.2 μs. Below this thickness it becomes difficult to form a semiconductor junction, and above this thickness each semiconductor layer acts as a barrier to one charge carrier, preventing the charge carrier from accelerating and resulting in no amplification effect. Can not. Furthermore, in order to generate an avalanche, a strong electric field from the outside, that is, 3X105v/c11 is required.
It is necessary to apply the above electric field and to have a potential energy difference at the junction interface of 1011ev to 5ev1, preferably 50IlleV to 3eV. Only by doing so will it be possible to generate more charge carriers than the number of photons of the irradiated electromagnetic waves and contribute to amplification.

In the present invention, the materials forming the charge transport layer include:
Hydrogenated amorphous silicon with controlled conductivity type, hydrogenated amorphous silicon carbide, hydrogenated amorphous silicon nitride, hydrogenated amorphous silicon oxide, selenium, selenium telluride, zinc oxide, aluminum oxide, zirconium oxide, etc., in inorganic semiconductors and polymers. Examples include organic charge transport materials in which low-molecular charge transport materials are dispersed, and these can be used in combination with a charge carrier amplification layer so that charges generated and amplified by electromagnetic waves can be efficiently injected and transported. The thickness of the charge transport layer is 0.
It is preferably in the range of 1 to 100111I, particularly preferably in the range of 1 to 50 fakes.

Materials for forming the charge injection blocking country include amorphous silicon whose conductivity type is controlled by group I or group V atoms, hydrogenated amorphous silicon carbide, hydrogenated amorphous silicon nitride, hydrogenated amorphous silicon oxide, amorphous carbon, Examples include inorganic semiconductors such as aluminum oxide and zirconium oxide, and polymer resins such as polycarbonate, polyester, and polyimide.
Preferably, it is set in the range of 0.1 to 10 g/ll.

Materials forming the surface layer include inorganic semiconductors such as hydrogenated amorphous silicon carbide, hydrogenated amorphous silicon nitride, hydrogenated amorphous silicon oxide, amorphous carbon, aluminum oxide, and zirconium oxide, polycarbonate, polyester,
A polymer resin such as polyimide or an organic film in which a low-molecular charge control material is dispersed in these polymers can be used. The thickness of the surface layer is preferably in the range of 0.05 to 20 #I, particularly preferably in the range of 0.1 to 10 IIIR.

In the present invention, each of the above layers can be created by any known method. For example, vacuum evaporation method, sputtering method, ion blating method, plasma CVD method, CV
It can be produced by the D method or the coating method.

Function As explained above, the electrophotographic photoreceptor according to the present invention includes a charge carrier amplification layer, p,
This electrophotographic photoreceptor is made by sequentially stacking at least two of p, p-1i, n-1n, and n-type semiconductor layers.
An avalanche region is formed by using a high electric field of 10'' V/art or more and a potential energy difference between conduction bands or valence bands of at least two semiconductor layers forming a charge carrier amplification layer as an electric field for accelerating charge carriers. As a result, the charge carriers generated by the electromagnetic waves absorbed inside the charge carrier amplification layer are amplified.In other words, the charge carriers injected into the avalanche region repeat collision ionization one after another and generate other ion pairs. as a result of which amplification of charge carriers can occur.

Example Next, the present invention will be explained in detail by way of examples.

Example 1 After loading an aluminum drum as a conductive substrate into a cylindrical plasma CVD reactor, the drum was heated while rotating to bring the substrate temperature to 300°C.

Next, open the gas introduction valve to the reactor and hydrogen 101005
The pressure inside the reactor was maintained at 0.51 orr.

After that, discharge with RF output of 100W for 10 minutes, and vacuum degree of 1
It was evacuated to 0 Torr.

Next, add 50 SCCm of silane, ioosccm of hydrogen gas, diborane diluted with hydrogen to silane, and add 1100 SCCm of diborane to the silane.
It was run so that it became pp. Under these conditions, the pressure is 0.51O
After setting to "r", discharge for 60 minutes with RF output of 100W,
A p-type amorphous silicon film with a thickness of 3 μ was formed as a charge injection blocking layer.

After discharging, the chamber was sufficiently exhausted. During this experiment, the discharge was stopped and sufficient exhaust air was provided between all the layers to be formed. Next, the gas introduction valve was opened, hydrogen 101005c and silane were introduced at 50 sccm, the pressure was set at 0.5 Torr, and discharge was performed at an RF output of 100 W for 10 minutes.

Next, add 100SCCII of hydrogen and 1ooscc+ of silane.
n was introduced, and diborane diluted with hydrogen was flowed so that the amount of diborane was 2 ppm relative to the silane. Under these conditions, the pressure is 0.
．． 5TORrk: After setting, 18 at RF output 150w
The discharge was carried out for 0 minutes, and a charge transport layer made of an i-type amorphous silicon film having a diameter of about 10 times was formed.

After the discharge was completed, the chamber was sufficiently evacuated, and the gas introduction valve was opened to introduce 30 sccm of hydrogen and 30 sccm of silane, and diborane diluted with hydrogen was flowed so that the amount of diborane was 30 ppm relative to the silane. After setting to 0.5 TOrr, RF
Discharge was performed for 2 minutes at an output of 50 W, and approximately 250 p-type amorphous silicon films were formed. Furthermore, after completion of the discharge, 30 SCCm of hydrogen and 30 SCCm of silane were introduced, and diborane diluted with hydrogen was flowed so that the amount of diborane was 2 ppm relative to the silane. Invasion set to 0.5 min orr, RF
Discharge was performed for 4 minutes at an output of 50 W, and approximately 500 i-type amorphous silicon films were formed. After discharging, hydrogen 30S
CCm and silane were introduced at 30SCCm, hydrogen-diluted phosphine was added to the silane, and phosphine was 1001)l)R
I ran it so that it was 1. Under these conditions, the pressure is 0.5 To
After setting to rr, RF specific output 0W is discharged for 2 minutes, about 2
Fifty n-type amorphous silicon films were formed. In this case, the formation of p-, i-, and n-type amorphous silicon films was roughly repeated twice in the same manner as above, and a charge carrier amplification layer having a charge generation region and an amplification region consisting of nine layers in total was formed. .

After discharging, add 50 SCCm of ethylene and 50 sc of silane.
After introducing cm and setting it to 0.5 Torr, RF output 1
A surface layer of about 2000 amorphous silicon carbide was formed by discharging at 00W for 20 minutes.

The photoreceptor thus prepared was positively charged while adjusting the corotron current, and the 4
The spectroelectrophotographic sensitivity of this photoreceptor was determined from the attenuation curve of the surface potential when irradiated with light of 00 nm to 800 nm.

The reflectance on the surface of the photoreceptor and the amount of absorption by the surface layer were corrected using the measured values of reflectance and absorbance, and the quantum efficiency of this photoreceptor was determined together with the amount of light. As a result, 5x10”
At a charging potential of 650 V, corresponding to an electric field of V/as, 70
The quantum efficiency becomes 1 or more at wavelengths shorter than 0 nm, and 500 nm
The maximum quantum efficiency was 2.0 at a wavelength of m. This demonstrated that charge carriers generated by photons formed an electron avalanche in the charge carrier amplification layer, resulting in amplification of the charge carriers.

Example 2 111 in the charge injection blocking layer! Using a silicon nitride film made with a flow rate ratio of n silane and ammonia of 2, 50 p-type and i-type layers were formed 20 times, for a total of 40 layers.
The manufacturing method was the same as in Example 1, except that a charge carrier amplification layer consisting of a charge generation region consisting of a layer and a charge carrier amplification layer consisting of an amplification region was formed.
A photoreceptor with the following configuration was manufactured.

The single-child efficiency of this photoreceptor was determined by the same method as in Example 1. As a result, 3
At a charging potential of 50 V, the quantum efficiency was 1 or more at wavelengths shorter than 750 nm, and the maximum quantum efficiency was 3.0 at a wavelength of 500 nm.

Example 3 A silicon nitride film prepared with a flow rate ratio of 1#I silane and ammonia of 2 was used as the charge injection blocking layer, and 50 n-type and i-type layers were formed by repeating 20 times. A photoreceptor was produced using the same manufacturing method and structure as in Example 1, except that a charge carrier amplification layer consisting of a charge generation region and an amplification region consisting of 40 layers was formed.

The quantum efficiency of this photoreceptor when negatively charged was determined in the same manner as in Example 1. As a result, at a charging potential of 350V, which corresponds to an electric field of 3X10"V/α, the quantum efficiency becomes 1 or more at wavelengths shorter than 7201m, and the maximum quantum efficiency is 500n[
The wavelength of Il was 2.5.

Effects of the Invention The electrophotographic photoreceptor of the present invention is composed of two or more semiconductor layers in which the charge carrier amplification layer, which is a component of the photoconductive layer, is different, and the internal potential energy formed by the semiconductor junction is The difference is used to accelerate charge carriers,
The charge carriers generated by the electromagnetic waves absorbed by the charge carrier amplification layer are exposed to 3X105V applied with reverse bias.
/a! Since electron avalanches can be repeatedly caused and amplified by a high electric field of 1 or more, it is possible to generate more charge carriers than the number of absorbed photons of the incident electromagnetic wave, that is, it is possible to increase the quantum efficiency to 1 or more. Therefore, the electrophotographic photoreceptor of the present invention has higher photosensitivity than conventionally known electrophotographic photoreceptors.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of the electrophotographic photoreceptor of the present invention. DESCRIPTION OF SYMBOLS 1... Conductive substrate, 2... Photoconductive layer, 3... Charge carrier amplification layer.

Claims (1)

[Claims] (1) A photoconductive layer including a charge carrier amplification layer is formed on a conductive support, and each charge carrier amplification layer has a thickness of 5 Å to
1μ, composed of at least two semiconductor layers with a potential energy difference between the conductor and/or valence band at the junction interface of 10meV to 5eV, and applied with a reverse bias of 3×10^5V/ An electrophotographic photoreceptor characterized in that the quantum efficiency of charge carrier generation by electromagnetic waves is 1 or more under an electric field of cm or more.