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E2.05 - Experimental Considerations for the Use of Fe2GeS4 Nanocrystals in Photovoltaics 
Date/Time:
April 22, 2014   11:45am - 12:00pm
 
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For long-term, economically competitive, sustainable solar energy to become a reality, absorber materials for photovoltaics should be selected for their earth abundance and low extraction costs. Iron pyrite, FeS2, has been proposed as an excellent candidate for these reasons, in addition to its reasonable band gap and large absorption coefficient. [1,2] Even though its photovoltaic properties were explored as early as the 1980’s and a recent resurgence in pyrite research has produced a number of publications, experimental studies have produced only poor results with regards to the photovoltaic properties. Many have attempted to explain the problems plaguing the material, but no experimental data has shown improved performance above the record 3% efficiency. [3]Recently, a class of materials has been proposed as an alternative to pyrite; Fe2MS4 (M = Si, Ge). Calculations have been used to predict nearly ideal photovoltaic properties (a band gap of 1.40 - 1.55 eV and a large absorption coefficient of 10^5 cm-1). [4] One hypothesis for the poor performance of pyrite is the possible decomposition of the desired phase to other iron-sulfur phases with very small band gaps. According to theory, there are no binary phases in the Fe2MS4 system that are calculated to be more stable than the ternary phase, suggesting it may be a significantly better candidate for solar cells because it may be more thermodynamically stable than the binary Fe-S pyrite phase. Historically, the bulk material has been studied for its interesting magnetic transitions as a function of temperature, but experimental reports of photovoltaic properties are limited. Herein, we report the synthesis of colloidal Fe2GeS4 nanocrystals for use in photovoltaic devices. The as-synthesized nanocrystals are phase-pure and form plate-like structures that show broad absorption in the visible region. While the nanocrystals exhibit poor stability under ambient conditions, methods of surface passivation for improved stability and enhanced photovoltaic properties will be discussed. These results pave the way towards a new earth-abundant material for use in low-cost photovoltaics.[1] Wadia, C.; Alivisatos, A. P.; Kammen, D. M. Environ Sci Technol 2009, 43, 2072.[2] Ennaoui, A.; Tributsch, H. Sol Cells 1984, 13, 197.[3] Ennaoui, A.; Fiechter, S.; Pettenkofer, C.; Alonsovante, N.; Buker, K.; Bronold, M.; Hopfner, C.; Tributsch, H. Sol Energ Mat Sol C 1993, 29, 289.[4] Yu, L.; Lany, S.; Kykyneshi, R.; Jieratum, V.; Ravichandran, R.; Pelatt, B.; Altschul, E.; Platt, H. A. S.; Wager, J. F.; Keszler, D. A.; Zunger, A. Adv. Energy Mater. 2011, 1, 748.
 


 
 
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