Molecular semiconductors containing diketopyrrolopyrrole and dithioketopyrrolopyrrole chromophores for small molecule or vapor processed solar cells

Abstract

Optoelectronic devices, such as photovoltaic devices, comprising a low band gap, solution processable diketopyrrolopyrrole or dithioketopyrrolopyrrole chromophore core or cores are disclosed. Also disclosed are methods of fabricating such optoelectronic devices.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority benefit of U.S. Provisional Patent Application No. 61 / 163,789, filed Mar. 26, 2009. The entire content of that application is hereby incorporated by reference herein in its entirety.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]This invention was made with Government support under grants N000140510677 and N000140811226 awarded by the Office of Naval Research, and grant DE-FG02-06ER46324 awarded by the Department of Energy. The Government has certain rights in this invention.BACKGROUND OF THE INVENTION[0003]Solar cells based on organic semiconductors are evolving into a promising cost-effective alternative to silicon-based solar cells due to low-cost fabrication by solution-processing, ease of processing, light weight, and compatibility with flexible substrates. Gunes et al. Chem. Rev. 2007, 107, 1324; Roncali, J., Acc. Chem. Res. 2009, 42, 1719. Devices based on these materials were ...

AI Technical Summary

Benefits of technology

The present invention is about an optoelectronic device that uses a mixture of a non-polymeric electron donor material and an electron acceptor material. The device includes a first hole-collecting electrode, an optional hole-transporting layer, a layer comprising a mixture of an electron donor material and an electron acceptor material, and a second electron-collecting electrode. The invention also includes a method of fabricating the device using solution processing. The non-polymeric electron donor materials include compounds of the diketopyrrolopyrrole structure. The invention also includes a photovoltaic device that uses a mixture of a non-polymeric electron donor material and an electron acceptor material. The non-polymeric electron donor materials can be selected from a variety of groups, such as thiophene, bithiophene, terthiophene, and benzothiophene. The invention also includes a method of fabricating the photovoltaic device using solution processing. The optoelectronic device can be used for various applications, such as photovoltaic devices.

Problems solved by technology

Although this system is capable of yielding some of the highest reported efficiencies among organic photovoltaics, it suffers from two significant shortcomings: i) the P3HT-PCBM mixture does not absorb light with wavelengths longer than about 650 nm, and thus a large fraction of sunlight is wasted in this system; and ii) the P3HT must have a relatively high molecular weight and very high regioregularity.

Synthesizing “good” P3HT can be problematic as the consistency between different batches of P3HT can vary.

Although such materials are successfully able to absorb a large fraction of the solar spectrum, most of them do not yield efficient BHJ photovoltaics due to inadequate electrical properties such as low charge carrier mobilities, incorrectly aligned HOMO and LUMO levels, or poor solid state morphologies.

However, the material is polymeric and there have been problems reproducing results using PCPDTBT from different sources.

Efficiencies as high as 6.5% have been reported using this type of system; however, fabricating two photovoltaic layers on top of each other adds a significant amount of complexity to the device architecture and difficulty in processing.

Fourth, the efficiencies observed in photovoltaics fabricated using this system are higher than those previously reported for solution-processed, non-polymeric photovoltaics.

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