Photoelectric conversion element, solar cell, and compound (fujifilm) electricity and circuits test

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This application is a Continuation Application of PCT Application No. PCT/JP2016/071423, filed Jul. 21, 2016, and based upon and claiming the benefit of priority from Japanese Patent Applications No. 2015-144420, filed Jul. 21, 2015; and No. 2016-046252, filed Mar. 9, 2016, the entire contents of all of which are incorporated herein by reference. BACKGROUND

Photoelectric conversion elements are used in a variety of optical sensors, copiers, solar cells, and the like. It is expected that solar cells will be actively put into practical use as cells using non-exhaustible solar energy. Examples of the type of the solar cells include a silicon type, a dye sensitized type, an organic thin film, and the like. Among these, research and development of dye sensitized solar cells, in which an organic dye, a Ru bipyridyl complex, or the like is used as a sensitizer, are actively in progress, and the photoelectric conversion efficiency thereof reaches approximately 11%.

Meanwhile, in recent years, there have been reported research results indicating that solar cells using a metal halide as a compound (hereinafter, also referred to as “perovskite compound” or “perovskite-type light absorbing agent”) having a perovskite-type crystal structure are capable of achieving relatively high photoelectric conversion efficiency, and the solar cells attract attention.

In addition, a solar cell using an A-D-A-type compound that is a composite of an acceptor (A) and a donor (D) as a hole transporting material’is described in J. Mater. Chem. A, 2015, 3, p. 11940 to 11947, and Energy Environ. Sci., 2014, 7, p. 2981 to 2985. SUMMARY

In a photoelectric conversion element or a solar cell which uses a perovskite compound, constant achievement is attained in an improvement of photoelectric conversion efficiency. However, the photoelectric conversion element or the solar cell which uses the perovskite compound has attracted attention in recent years, and little is known about battery performance other than photoelectric conversion efficiency.

The photoelectric conversion element and the solar cell are required to have durability capable of maintaining initial performance in a field circumstance in which the photoelectric conversion element and the solar cell are actually used in addition to high photoelectric conversion efficiency.

However, it is known that the perovskite compound is easily damaged under a high-humidity environment or a high-humidity and heat environment. Actually, in a photoelectric conversion element or a solar cell which uses the perovskite compound as a light absorbing agent, photoelectric conversion efficiency greatly deteriorates under the high-humidity environment or the high-humidity and heat environment in many cases. In addition, a problem of a moisture resistance variation is also pointed out.

With regard to a cause for generation of the variation in the moisture resistance, it is assumed that the perovskite compound is decomposed due to intrusion of water from a defect in an interface between the perovskite compound and the hole transporting material or moisture that is contained in the hole transporting material. In J. Mater. Chem. A, 2015, 3, p. 11940 to 11947, and Energy Environ. Sci., 2014, 7, p. 2981 to 2985, an A-D-A type hole transporting material that does not uses a hydrophilic additive (LiTFSI and the like) is used. From a result obtained through extensive study made by the present inventors, it could be understood that the moisture resistance variation can be suppressed to a certain extent in a case of using the hole transporting material, but the suppression is not sufficient. The reason for this is considered to be because it is difficult to suppress intrusion of water from a defect in a material interface and the like.

The invention has been made in consideration of the above-described circumstances, and an object thereof is to provide a photoelectric conversion element which uses a perovskite compound as a light absorbing agent in a photosensitive layer and in which a moisture resistance variation is suppressed. In addition, another object of the invention is to provide a solar cell including the photoelectric conversion element. In addition, still another object of the invention is to provide a new compound that is appropriately used in the photoelectric conversion element.

The present inventors have obtained the following finding. In a photoelectric conversion element or a solar cell which uses a perovskite compound as a light absorbing agent, as a hole transporting material, in a case of using an A-D-A-type compound that is a composite of an acceptor (A) and a donor (D), and has a ring structure including two kinds of specific hetero atoms in a ring at D (donor) or a linking portion between D (donor) and A (acceptor), a moisture resistance variation is improved. The invention is accomplished by further repeating examinations on the basis of the finding.

[1] According to an aspect of the invention, there is provided a photoelectric conversion element comprising, at least: a first electrode that includes a conductive support; a photosensitive layer that contains a light absorbing agent; a hole transport layer that contains an organic hole transporting material; and a second electrode, at least one of the photosensitive layer or the hole transport layer being provided on the conductive support to constitute the first electrode in combination with the conductive support.

The photosensitive layer includes at least a compound having a perovskite-type crystal structure that includes a cation of an element of Group 1 in the periodic table or a cationic organic group A, a cation of a metal atom M other than elements of Group 1 in the periodic table, and an anion of an anionic atom or atomic group X as the light absorbing agent.