JPS5989473A - Photoelectric conversion element - Google Patents

Abstract

PURPOSE:To improve sensitivity, and to mass-produce the converters by simultaneously forming a plurality of minute photo-EMF element patterns on one substrate while simultaneously obtaining a differential type electric coupling. CONSTITUTION:A plurality of lower electrodes 5a, 5b are formed to the insulating substrate 5, and an amorphous silicon thin-film 6 is formed on the electrodes. A plurality of upper electrodes 7a, 7b are formed on the thin-film 6. At least one side of the electrodes 5a, 5b and the electrodes 7a, 7b are formed in transparent electrodes. A plurality of photosensors are formed by the thin-film 6, the electrodes 5a, 5b and the electrodes 7a, 7b. Electrode patterns are formed so that the polarity of the adjacent photosensors is connected reversely in succession. When a shielding plate 3 is moved laterally, beams are projected alternately to the electrodes 7a, 7b, and photo-EMF is generated alternately in two photo-EMF elements.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an amorphous thin film photoelectric conversion element applied to photoelectric encoders and the like.

Structure of a conventional example and its problems FIG. 1 is a block diagram of a photoelectric encoder using a photodiode 4 of a conventional example. A photodiode 4 as a light receiving element is arranged opposite to a light source 1 such as a light emitting diode or an incandescent lamp, and a baffle plate 3 having continuous openings 2 at an appropriate pitch is arranged therebetween.

The photodiode 4 is a PMN junction diode made of single crystal silicon, and a voltage is applied to the lead wire 4J4b so that a reverse bias is applied to the PN junction.

When the shielding plate 3 moves laterally in the figure, intermittent light enters the PN junction of the photodiode 4, and carriers generated generate photocurrent signals in the lead wires 4a and 4b as shown in FIG. That is, the number of pulses corresponding to the amount of movement of the shielding plate 3 is generated, and the analog displacement can be quantified. The drawbacks of this conventional example are that the generated photocurrent is small, the sensitivity is low due to pulsating current, and it is susceptible to noise.

! The shape of the photodiode 4 is large, for example, the outer diameter is about 3 mm.
■φ, the light receiving part is about 1■φ, and the resolution for displacement is poor.Furthermore, the thickness of the photodiode element is 2 to 3 mm, making it impossible to reduce the thickness of the entire encoder. The distance between the shielding plate 3, the light source 1, and the photodiode 4 is about 0.5 to 1 space, respectively.

OBJECTS OF THE INVENTION The present invention provides a photoelectric conversion element for an encoder that is small, highly sensitive, and highly efficient.

Structure of the Invention The present invention provides a photovoltaic device using an amorphous silicon thin film that can simultaneously form a plurality of microscopic photovoltaic device patterns on a single substrate and also provide differential electrical coupling. It is a conversion element.

DESCRIPTION OF EMBODIMENTS FIG. 3 shows an embodiment. Two lower electrodes 5a are placed on an insulating substrate 5 made of glass, ceramic, heat-resistant polymer film, etc.
, 5b. The formation method is to deposit nickel, nickel-chromium alloy, chromium, aluminum, titanium, ITO (NxSn1-xO3), 5N02, etc. using electron beam evaporation using a vacuum evaporation cis-buttering device. Next, using Brozma CVD equipment,
．． Glow discharge is generated at a pressure of 1 to 4 Torr and 150 to
An amorphous silicon semiconductor thin film 6 is formed on a substrate 4 heated to 300°C. In this amorphous silicon, unbonded dangling bonds are compensated by H atoms generated by decomposition of silane (SiH4), and the localized levels in the band gap are significantly reduced. Therefore, if a gas containing an impurity element is mixed during discharge, the impurities can be controlled to make the semiconductor a P-type or N-type semiconductor. Therefore, diborane (82H6)
First, in a silane gas containing 0.2 to 2 parts of
0A P-type amorphous silicon layer, then 3000~5000A 1 amorphous silicon layer without impurities, and finally 50~50A in 7 run gas containing 0.2~2% phosphine (PH3). A 5000A N-type amorphous silicon layer is formed to form an amorphous silicon semiconductor thin film 6 having a PiN structure. Further, upper electrodes 7a and 7b are formed in the same manner as the lower electrode. In the case of the embodiment shown in FIG. 3, the upper electrodes 7a and 'yb serving as the light-receiving surface must be at least transparent electrodes, and are made of ITO or SnOz. FIG. 4 is a sectional view of the embodiment of the photoelectric conversion element shown in FIG. 3. In FIG. 3, two photovoltaic elements are formed on one insulating substrate 5 at the same time, a transparent upper electrode 7a is in electrical contact with a lower electrode 5b of an adjacent photovoltaic element, and a transparent The upper electrode 7b is also patterned to electrically contact the lower electrode 5a of the adjacent photovoltaic element. Therefore, as shown in the circuit diagram of FIG. 5, two photovoltaic elements are connected in series. In FIG. 3, the distance between the transparent upper electrodes 7a and 7b is half the pitch of the openings 2, so when the shield plate 3 moves laterally, light alternately enters the upper electrodes 7a and 7b. Then, photovoltaic force is generated alternately in the two photovoltaic elements. Therefore, an alternating current photocurrent as shown by the dotted line in FIG. 8 flows through the lead wires s h and s b. Since the two photovoltaic elements are, so to speak, the same as solar cells, there is no need for a bias power source as in the conventional example.

As is clear from the above description, it is very easy to form two or more photovoltaic elements on a single insulating substrate, and an example thereof is shown in FIG. A comb-shaped common lower electrode 10, 11 (for the i7 setup, an amorphous silicon thin film 12, which becomes a common film in the plasma+4D device) is provided on a single insulating substrate 9, and transparent upper electrodes 13, 14, . 15i electrically contacts the common lower electrode 1o of adjacent photovoltaic elements, and the transparent upper electrode 16, 17, 18'i electrically contacts the common lower electrode 11 of adjacent photovoltaic elements. Figure 7 is an electrical circuit diagram of the elements in Figure 6.Since every other photovoltaic element is connected in parallel and the light is turned on and off at the same time, the photocurrent is After being integrated, an alternating current photocurrent with high sensitivity as shown by the solid line in FIG. 8 flows through the lead wires 19 and 20.

The upper electrodes 13 to 18 in FIG.
It is possible to create a fine pattern of 0μ, and if the openings 2 of the barrier plate 3 are photo-etched in the same way to a width of 5μ, the pattern will be 1 hole for every 0.1μ movement of the barrier plate 3. A very high-resolution encoder that generates a pulse signal can be easily realized. The shielding plate 3 is made into a disk, and the openings 2 are arranged on its circumference, and photovoltaic elements are formed at a pitch of 0.1w to 50μ on the outer periphery of a circular insulating substrate so as to face it. However, it is also possible to create an encoder that detects displacement due to rotation. Even if the photoelectric conversion element shown in Fig. 6 is large, for example, 5.0 mm, 400 elements can be obtained from one substrate by forming an amorphous silicon thin film and photoetching the electrodes on a substrate size of 100 +++ m2. It is mass produced.

It's cheap. Since it is photo-etched, the dimensional accuracy of element placement is also high.
In the figure, the insulating substrate 5 is made of transparent glass and the lower electrodes 5a, 5
If b is a transparent electrode, it is also possible to make it face the baffle plate 3 so that light enters from the substrate side. Also the 9th
As in the embodiment shown in the figure, a thin insulating film 21 such as SiO2 or SiN is provided on a metal plate 25 made of stainless steel or aluminum to form a substrate, and this is used to improve the workability of the substrate or to shield electromagnetic induction. In the above embodiment, a continuous amorphous silicon thin film was formed for a plurality of electromagnets, but separate amorphous silicon thin films may be used for each electrode.

Effects of the Invention As described above, according to the present invention, multiple photovoltaic elements are coupled in a differential type, so sensitivity is high, and since it is made of amorphous silicon, mass production is possible, low cost, and small size. Since a pattern can be formed by photoetching, an excellent encoder-related photoelectric conversion element with high resolution can be obtained.

[Brief explanation of drawings]

Figure 1 is a block diagram of an encoder using a conventional photodiode, Figure 2 is a diagram showing the photocurrent of the photodiode in Figure 1, and Figure 3 is an encoder using a photoelectric conversion element according to an embodiment of the present invention. A configuration diagram of the encoder, FIG. 4 is a cross-sectional view of the photoelectric conversion element in FIG. 3, and FIG. 5 is an electric circuit diagram of FIG. 3.
6 is a top view of a photoelectric conversion element according to an embodiment of the present invention, FIG. 7 is an electric circuit diagram of FIG. 6, and FIG. 8 is a diagram showing photocurrent generated at terminals 19 and 20 in FIG. 7. , FIG. 9 is a sectional view of a photoelectric conversion element according to a different embodiment of the present invention. 5... Insulating plate, 5iL, 5b... Lower electrode, 6... Amorphous silicon thin film, 7a, 7
b... Upper electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person46
3 Figure 2 Special Edition Figure 5 Figure 7 Figure 0 Phantom 'o-f'3b '''

Claims (1)

[Claims] A plurality of lower electrodes are provided on an insulating substrate, an amorphous silicon thin film is formed thereon, a plurality of upper electrodes are provided thereon facing the lower electrodes, and at least one of the upper electrodes and the lower electrodes. is a transparent electrode, a plurality of photovoltaic elements are formed by the amorphous silicon thin film and a lower electrode and an upper electrode sandwiching it, and an electrode pattern is formed so that the polarities of adjacent photovoltaic elements are connected in reverse order. photoelectric conversion element.