Ecotoxicological assessment of solar cell leachates

Abstract

The present and future coverage of energy consumption relies on photovoltaics. Still an open issue remains the potential ecotoxicological implications in the production, use and in particular disposal of photovoltaic devices after discarded on landfills, shredded, or burned. Here we compare potential ecotoxicological effects of two thin-film photovoltaics, an established copper indium gallium selenide (CIGS) photovoltaic cell and an organic photovoltaic (OPV) cell, which is under development in the EU-sponsored project, SUNFLOWER. Leachates from these photovoltaics were created by physically damaging the cells and adding them to environmentally relevant model waters representing mesotrophic lake water, acidic rain, and seawater conditions. To assess the ecotoxicological effects of the different leachates, zebrafish embryos were exposed for 120 h. Thereby, morphological as well as transcriptional effects were assessed. Leachates originating from CIGS cells in conditions of acidic rain or seawater caused a severe hatching delay in zebrafish embryos, while CIGS leachates simulating lake water and all OPV leachates allowed normal embryonic development. By adding EDTA, a metal chelator, the hatching delay could be restored. This suggests that metals released from the CIGS cell fragments represent the major toxic moiety for the observed effect. Changes in gene expression disclosed not only the activation of metallothionein, but moreover of genes involved in oxidative stress (catalase) and endocrine system (vitellogenin). ICP-MS analysis showed that different metal(loid)s were present in the leachates depending on the exposure regime and type of photovoltaic. In lake water, only molybdenum leached from CIGS cells, whereas at conditions simulating acidic rain and sea water a mixture of iron, copper, zinc, molybdenum, cadmium, silver, and tin leached from CIGS. From OPV, only zinc and silver were released. Our study shows that CIGS cells may have potential ecotoxicological effects at their end of life, whereas OPV represent an environmentally friendly alternative to CIGS photovoltaic cells.

Full text

ECOTOXICOLOGICAL ASSESSMENT OF SOLAR CELL LEACHATES
N.R. Brun1,2*, B. Wehrli2, K. Fent1,2
1 University of Applied Sciences and Arts Northwestern Switzerland, School of Life Sciences,
Gründenstrasse 40, 4132 Muttenz, Switzerland
2 Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, Universitätsstrasse 16, 8092
Zürich, Switzerland
*Presenting author: nadja.brun@fhnw.ch
The present and future coverage of energy consumption relies on photovoltaics. Still an open issue
remains the potential ecotoxicological implications in the production, use and in particular disposal
of photovoltaic devices after discarded on landfills, shredded, or burned. Here we compare potential
ecotoxicological effects of two thin-film photovoltaics, an established copper indium gallium
selenide (CIGS) photovoltaic cell and an organic photovoltaic (OPV) cell, which is under
development in the EU-sponsored project, SUNFLOWER. Leachates from these photovoltaics were
created by physically damaging the cells and adding them to environmentally relevant model waters
representing mesotrophic lake water, acidic rain, and seawater conditions. To assess the
ecotoxicological effects of the different leachates, zebrafish embryos were exposed for 120 h.
Thereby, morphological as well as transcriptional effects were assessed.
Leachates originating from CIGS cells in conditions of acidic rain or seawater caused a severe
hatching delay in zebrafish embryos, while CIGS leachates simulating lake water and all OPV
leachates allowed normal embryonic development. By adding EDTA, a metal chelator, the hatching
delay could be restored. This suggests that metals released from the CIGS cell fragments represent
the major toxic moiety for the observed effect. Changes in gene expression disclosed not only the
activation of metallothionein, but moreover of genes involved in oxidative stress (catalase) and
endocrine system (vitellogenin). ICP-MS analysis showed that different metal(loid)s were present in
the leachates depending on the exposure regime and type of photovoltaic. In lake water, only
molybdenum leached from CIGS cells, whereas at conditions simulating acidic rain and sea water a
mixture of iron, copper, zinc, molybdenum, cadmium, silver, and tin leached from CIGS. From
OPV, only zinc and silver were released. Our study shows that CIGS cells may have potential
ecotoxicological effects at their end of life, whereas OPV represent an environmentally friendly
alternative to CIGS photovoltaic cells.
Keywords: photovoltaics, zebrafish embryo, metal toxicity, transcriptional changes