Eco-design for perovskite solar cells to address future waste challenges and recover valuable materials

Abstract

Photovoltaic development should be steered by the circular economy. However, it is not. In case of perovskite photovoltaics even current environmental directives divert from profitably recycling. Here, we study the profitability of noble metals recovery from wasted perovskite solar cells depending on recycling routes. Our results show that substrates play a major role in the recovery of precious metals and in contrast to previous research even recycling carbon-based devices could reach profitability. Going beyond the recovery of valuable elements, our findings show that revival of the perovskite solar cells is strongly dependent on the device architecture, so far viable for mesoscopic structures with carbon back contacts. Perovskite solar cells are still at the development stage, but the window of opportunity to ensure eco-design will close with market entry, and device complexity might compromise profitability recycling and even result in failure of recovery critical materials. Therefore, its eco-design should be prioritized by materials researchers to develop devices, where valuable components can be separated and liberated with safe and low energy processes.

Keywords: Circular economy; Eco-design; Material development; Perovskite solar cells; Photovoltaics; Recycling.

Fig. 1

Perovskite solar cells architectures and materials: (a) – common configurations in which the perovskite layer is sandwiched between the charge selective layers as hole transport layer (HTL) and the electron transport layer (ETL). In inverted (p–i–n) structures HTL and ETL are reversed; (b) – mesoscopic structure containing a multi-layer mesoporous architecture such as TiO₂/ZrO₂/carbon deposited on conductive substrate in sequence with infiltrated perovskite.

Fig. 2

Amount (g/ton) of noble and potentially harmful elements which could be potentially recovered (100% recovery rate) depending on different substrate scenarios. For profitability calculations Spiro-OMeTAD and PCBM were selected as charge transport layers among the expensive ones (Table 1). For substrate pre-detachment scenario (No substrate), elements amounts were calculated based on weight of concentrated waste - the layers left after substrate removal. Noble metals profit thresholds were estimated assuming 80% recovery rate. Pb hazard threshold according to Directive 2011/65/Eu [57], restricting the use of certain hazardous substances in electrical and electronic equipment. The colors indicating the elements (Au – purple, Ag – blue, Pb – red) are marked with dark colors when going above a threshold either in profit or hazard. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3

Levels of recycling for perovskite solar technology. Higher levels of recycling preserve economic value. If reviving the perovskite solar cells fails for several reasons, including the end-of-life of the perovskite layer, the photovoltaic devices can be recycled to reuse the valuable components by disassembling and reassembling the layers. If the compounds are expensive, scarce, or harmful, the incentive to recycle increases. When recovering elements is the only option, the main economic incentive originates from precious metals.

Fig. 4

Au profitability sensitivity.

Fig. 5

Ag profitability sensitivity.