New design principles boost performance of solar cells

-

 

-

Figure 2. a) Photophysical processes and corresponding generation/dissociation/recombination rates in organic solar cells during device operation. b) Model bilayer device architecture. c) Strategies used to insert spacer layers at the P3HT/C 60 [regio-regular Poly(3-hexylthiophene-2, 5-diyl /fullerene] interface and the energy level alignment of P3HT (donor) and C 60 (acceptor) with respect to spacer levels. d) Molecular structures of O3 [terthiophene-derivative], Irpiq [(bis(1-phenylisoquinoline)-(acetylacetonate) iridium (III)], and Irppy [tris(2-phenylpyridine)iridium (Irppy)] spacer layers. e) Photocurrent versus excitation wavelength measured under short-circuit conditions without (dashed black curve) and with (solid color curves) spacer layers. Peaks in the photocurrent spectra match well with the absorbance of P3HT.

-

Los Alamos researchers and University of Minnesota collaborators cleared what they call a long- standing bottleneck in the field of organic electronic devices. The team has discovered key interface charge transport dynamics that must be understood in order to control charge and energy transport across interfaces in organic electronics. In addition, the scientists have demonstrated interface design principles that could significantly raise power conversion efficiency in organic solar cells. When applied to practical device architectures such as bulk heterojunction solar cells, these strategies can boost the overall power conversion efficiency from approximately 4.0% to greater than 7.0%. Advanced Science published the findings.

The researchers investigated three distinct types of interface functional spacer layers between the donor and acceptor of an organic photovoltaics device. The results demonstrated that the power conversion efficiency can be dramatically improved by as much as approximately 2–5 times in a model bilayer device. The three independent interface modification strategies dramatically suppress the interface charge-transfer (CT) state recombination. Similar interface design strategies could be applicable to a wide range of hybrid material systems with organic–inorganic and inorganic– inorganic interfaces such as perovskite solar cells, atomic layered 2-D interfaces, nanostructured systems such as quantum dots, and single-wall carbon nanotubes for the development of next generation, high efficiency light to energy conversion optoelectronic devices.

Reference: “Interface Design Principles for High-Performance Organic Semiconductor Devices,” Advanced Science 2, 1500024 (2015); doi: 10.1002/advs.201500024). Authors include: Wanyi Nie, Gautam Gupta, Brian Crone, and Aditya Mohite (Material Synthesis and Integrated Devices, MPA-11); Darryl Smith (Physics of Condensed Matter and Complex Systems, T-4); Hui Li (Nuclear and Particle Physics, Astrophysics and Cosmology, T-2); Sergei Tretiak (Physics and Chemistry of Materials, T-1); Cheng-Yu Kuo, Hsinhan Tsai, and Hsing-Lin Wang (Physical Chemistry and Applied Spectroscopy, C-PCS); Feilong Liu and P. Paul Ruden (University of Minnesota).

The DOE Office of Basic Energy Sciences and the Los Alamos Laboratory Directed Research and Development (LDRD) program funded different aspects of the work, which supports the Laboratory’s Energy Security mission area and Materials for the Future science pillar through technological advances in solar energy. Technical contact: Aditya Mohite