CROSS REFERENCE TO RELATED APPLICATIONS

This application is a 35 U.S.C. § 371 national stage application of PCT International Application No. PCT/KR2019/002230, filed Feb. 22, 2019, which claims priority from Korean Patent Application No. 10-2018-0028135, filed Mar. 9, 2018, the contents of which are incorporated herein in their entireties by reference. The above-referenced PCT International Application was published in the Korean language as International Publication No. WO 2019/172562 on Sep. 12, 2019.

TECHNICAL FIELD

The present specification relates to a composition for an organic material layer of an organic solar cell, and an organic solar cell.

BACKGROUND ART

An organic solar cell is a device capable of directly converting solar energy to electric energy by applying a photovoltaic effect. Solar cells are divided into inorganic solar cells and organic solar cells depending on the materials forming a thin film. Typical solar cells are fabricated using a p-n junction by doping crystalline silicon (Si), an inorganic semiconductor. Electrons and holes generated by light absorption spread to p-n junction points, are accelerated by the electric field, and migrate to an electrode. Power conversion efficiency of this process is defined as a ratio of power given to an external circuit and solar power put into a solar cell, and the ratio has been accomplished up to approximately 24% when measured under a currently standardized hypothetical solar irradiation condition. However, existing inorganic solar cells already have limits in economic feasibility and material supplies, and therefore, organic material semiconductor solar cells that are readily processed, inexpensive and have various functions have been highly favored as a long-term alternative energy source.

For solar cells, it is important to increase efficiency so as to output as much electric energy as possible from solar energy. In order to increase efficiency of such solar cells, generating as much excitons as possible inside a semiconductor is important, however, taking the generated charges outside without loss is also important. One of the reasons for the charge loss is the dissipation of the generated electrons and holes by recombination. Various methods for delivering the generated electrons or holes to an electrode without loss have been proposed, however, most of the methods require additional processes, and accordingly, the fabricating costs may increase.

DISCLOSURE

Technical Problem

The present specification is directed to providing a composition for an organic material layer of an organic solar cell, and an organic solar cell including the composition.

Technical Solution

One embodiment of the present specification provides a composition for an organic material layer of an organic solar cell including an electron donor including a polymer including a first unit represented by the following Chemical Formula 1, a second unit represented by the following Chemical Formula 2, and a third unit represented by the following Chemical Formula 3 or 4; and a non-fullerene-based electron acceptor.



In Chemical Formulae 1 to 4,

X1 to X6 are the same as or different from each other, and each independently CRR′, NR, O, SiRR′, PR, S, GeRR′, Se or Te,

Y1 and Y2 are the same as or different from each other, and each independently CR″, N, SiR″, P or GeR″,

A1 and A2 are the same as or different from each other, and each independently a halogen group,

Cy1 is a substituted or unsubstituted heteroring,

Q1 and Q2 are the same as or different from each other, and each independently O or S, and

R, R′, R″ and R1 to R8 are the same as or different from each other, and each independently hydrogen; deuterium; a halogen group; a nitrile group; a nitro group; an imide group; an amide group; a hydroxyl group; a substituted or unsubstituted alkyl group; a substituted or unsubstituted cycloalkyl group; a substituted or unsubstituted alkoxy group; a substituted or unsubstituted aryloxy group; a substituted or unsubstituted alkylthio group; a substituted or unsubstituted arylthio group; a substituted or unsubstituted alkylsulfoxy group; a substituted or unsubstituted arylsulfoxy group; a substituted or unsubstituted alkenyl group; a substituted or unsubstituted amine group; a substituted or unsubstituted aryl group; or a substituted or unsubstituted heterocyclic group.

Another embodiment of the present specification provides an organic solar cell including a first electrode; a second electrode disposed opposite to the first electrode; and one or more organic material layers disposed between the first electrode and the second electrode and including a photoactive layer, and one or more layers of the organic material layers include the composition for an organic material layer of an organic solar cell described above.

Advantageous Effects

A polymer according to one embodiment of the present specification is an electroconductive material, and has thermal stability, excellent solubility and high electron mobility. Accordingly, excellent electrical properties can be obtained when used in an organic solar cell.

In addition, the polymer according to one embodiment of the present specification has a high HOMO energy level, and when obtaining an organic solar cell including the same, excellent efficiency is obtained.

By using the polymer described in embodiments of the present specification in an organic solar cell together with a non-fullerene-based electron acceptor, battery efficiency can be enhanced. The non-fullerene-based electron acceptor has advantages in that an absorption wavelength region of light is readily controlled compared to existing fullerene-based electron acceptors such as PCBM, and the absorption wavelength region can be controlled so as not to overlap with an absorption wavelength region of an electron donor increasing a short circuit current, and thermal stability is superior since an aggregation phenomenon in which electron acceptor materials aggregate with each other occurs less compared to fullerene-based electron acceptors. In order to obtain favorable efficiency with such a non-fullerene-based electron acceptor, an electron donor of which absorption wavelength does not overlap and having proper HOMO and LUMO energy levels needs to be used, and the polymer according to one embodiment of the present specification satisfies such properties and can form proper morphology with the non-fullerene-based electron acceptor.

