Novel Formulation Accelerates Further Efficiency Gains for Solar Cells
RESEARCH TRIANGLE PARK, N.C., May 14, 2012 – DuPont™ Solamet® PV17x photovoltaic metallization paste has become the leading frontside silver paste series on the market today due to its ability to raise efficiency in standard solar cell constructions and its unique properties which enable Lightly Doped Emitter (LDE) cell designs. LDE is a strong differentiator for solar cell producers as it can boost efficiency by up to 0.4 percent. DuPont Microcircuit Materials is taking steps to increase its supply capability for Solamet® PV17x to help meet the increased demand for higher efficiency solar cells.
"Solamet® PV17x series continue to advance technology to help meet the industry's goal of 20 percent efficiency by 2012," said Peter Brenner, photovoltaics global marketing manager, DuPont Microcircuit Materials. "This product has a two-stage advantage, since on its own it can raise efficiency by up to 0.2 percent, and when used to enable LDE, can raise efficiency by up to 0.4 percent. We're very pleased to see such strong demand and are working to quickly increase supply capability for the growing customer base as it becomes qualified in stages through the next three months."
Solamet® PV17x is the most advanced composition in the market allowing for contact to be made to the most lightly doped junctions. Doping diffusion optimization is a key area of experimental study in the photovoltaic industry for the design of high efficiency cells. Diffusion optimization has been significantly limited by the inability of traditional frontside photovoltaic silver pastes to contact lightly surface doped emitters. Prior to Solamet® PV17x being released, the industry had no real commercially available option for making a screen printed frontside metallization that could economically and practically enable an LDE. However, the excellent silicon to silver contact of DuPont™ Solamet® PV17x technology has demonstrated its capability to enable a wider range of diffusion optimization and higher cell efficiency.
Extensive testing is underway within DuPont and in collaboration with several research organizations as well as in customer trials to fully characterize and continue to advance this technology. For example, RWTH-Aachen University recently published a comparative study involving Solamet® PV17x and four competing metallization pastes. Solamet® PV17x outperformed four competing products, demonstrating its ability to contact 100 Ohm/sq emitters on multicrystalline cells – the first time this had been achieved - with lightly doped phosphorous surface concentration. This enabled an efficiency increase of one full percent versus the homogenous emitter base line and 0.4 percent higher efficiency was confirmed versus laser doped selective emitter technologies.
"We presented a characterization of POCl3 parameters influencing the electrically active phosphorus concentration profiles by electrochemical capacitance voltage measurements," said Ali Safiei, (PhD researcher), Institute of Semiconductor Electronics at RWTH Aachen University. "For the first time we could demonstrate a successful direct contacting of an optimized high sheet resistance emitter at 100 Ω/sq by increasing the n++ layer and at the same time reducing the dead layer. Multicrystalline silicon solar cells were fabricated using five different silver pastes resulting in an absolute efficiency gain of Δη = 1 percent in comparison to a standard 55 Ω/sq emitter. Based on these investigations we evaluated a 160 Ω/sq emitter and could successfully demonstrate by laser doping that a n++ layer of up to 25 nm depth (a Lightly Doped Emitter) leads to high FF and an absolute efficiency gain of Δη > 0.6 percent."
The breakthrough formulation of Solamet® PV17x also enables cell makers to use up to 15 percent less material, in line with the company's intent to accelerate product developments that help the photovoltaic industry reduce its dependence on silver metals and offset some of the impact that rising silver prices have on the cost of producing solar cells and modules.
Continued development on next generation Solamet® metallizations is ongoing with the aim of continuing to improve efficiency and further integrating Solamet® pastes with complementary processes such as LDE and local back surface field (LBSF) cell architectures.
DuPont MCM has over 40 years of experience in the development, manufacture, sale and support of specialized thick film compositions for a wide variety of electronic applications in the photovoltaic, display, automotive, biomedical, industrial, military and telecommunications markets. For more information on DuPont Microcircuit Materials and Solamet® metallization pastes, please visit http://mcm.dupont.com.
DuPont™ Solamet® photovoltaic metallizations are part of a broad and growing portfolio of products represented by DuPont Photovoltaic Solutions (DPVS), which connects science and technology from across the company on a global scale to help support the dramatic growth in the photovoltaic industry. To learn more, please visit http://photovoltaics.dupont.com.
DuPont (NYSE: DD) has been bringing world-class science and engineering to the global marketplace in the form of innovative products, materials, and services since 1802. The company believes that by collaborating with customers, governments, NGOs, and thought leaders we can help find solutions to such global challenges as providing enough healthy food for people everywhere, decreasing dependence on fossil fuels, and protecting life and the environment. For additional information about DuPont and its commitment to inclusive innovation, please visit http://www.dupont.com.