Cumulative energy demand for small molecule and polymer photovoltaics

Abstract

ABSTRACTOrganic photovoltaics (OPVs) are expected to be a low cost, environmentally friendly energy solution with advantageous properties such as flexibility and light weight that enable their use in new applications. Considerable progress in power conversion efficiencies has brought OPV technology closer to commercialization. However, little consideration has been given to potential environmental impact associated with their production. Although environmental life cycle studies of OPV exist, their scope is narrow or too reliant on outdated technologies. Some of the most significant recent improvements are the result of new semiconductors materials, which have not yet been assessed from a life cycle perspective. Therefore, this study calculates life cycle embodied energy for 15 new materials encompassing a variety of donor, acceptor, and interface compounds showing the most promise in organic electronics. With the use of new inventory data, life cycle energy impact associated with production of both single junction and multi‐junction architectures has been calculated including bulk heterojunction polymer, planar small molecule, and planar‐mixed small molecule devices. The cumulative energy demand (CED) required to fabricate small molecule and polymer photovoltaics were found to be similar from 2.9 to 5.7 MJ/Wp. This CED is on average of 50% less than for conventional inorganic photovoltaics, motivating the continued development of both technologies. The use of fullerenes was shown to have a dramatic impact on polymer solar cells, comprising 18–30% of the CED, despite only being present in small quantities. Increases in device efficiency are shown to marginally reduce CED for both small molecule and polymer designs. Copyright © 2012 John Wiley & Sons, Ltd.