Synthesis cost dictates the commercial viability of lead sulfide and perovskite quantum dot photovoltaics

Abstract

Any new solar photovoltaic (PV) technology must reach low production costs to compete with today's marketleading crystalline silicon and commercial thin-film PV technologies. Colloidal quantum dots (QDs) could open up new applications by enabling lightweight and flexible PV modules. However, the cost of synthesizing nanocrystals at the large scale needed for PV module production has not previously been investigated. Based on our experience with commercial QD scale-up, we develop a Monte Carlo model to analyze the cost of synthesizing lead sulfide and metal halide perovskite QDs using 8 different reported synthetic methods. We also analyze the cost of solution-phase ligand exchange for preparing deposition-ready PbS QD inks, as well as the manufacturing cost for roll-to-roll solution-processed PV modules using these materials. We find that present QD synthesis costs are prohibitively high for PV applications, with median costs of 11 to 59 $ per g for PbS QDs (0.15 to 0.84 $ per W for a 20% efficient cell) and 73 $ per g for CsPbI 3 QDs (0.74 $ per W). QD ink preparation adds 6.3 $ per g (0.09 $ per W). In total, QD materials contribute up to 55% of the total module cost, making even roll-to-roll-processed QDPV modules significantly more expensive than silicon PV modules. These results suggest that the development of new low-cost synthetic methods is critically important for the commercial relevance of QD photovoltaics. Using our cost model, we identify strategies for reducing synthetic cost and propose a cost target of 5 $ per g to move QD solar cells closer to commercial viability. Broader contextColloidal quantum dots (QDs) have been widely investigated as an avenue toward ultra-low-cost solar photovoltaics (PV), alongside organics and metal halide perovskites. It is often implicitly assumed-and explicitly stated-that QD-based PV technologies can reach low cost because they employ low-cost, abundant elements and low-temperature, high-throughput manufacturing processes. However, this argument holds true only if QDs can be synthesized at low cost-materials dictate the module cost floor. Here we report the first detailed analysis of the cost of large-scale QD synthesis for PV applications. Our Monte Carlo approach constitutes a complete cost modeling framework for QD photovoltaics, from raw precursors to finished modules. We find that QD synthesis is prohibitively expensive today, highlighting the importance of synthetic cost for the commercial viability of QD solar technologies and guiding further research toward promising synthetic directions.

Decreased Synthesis Costs and Waste Product Toxicity for Lead Sulfide Quantum Dot Ink Photovoltaics

“…In a separate synthetic step, OAcapped PbS QDs are exchanged with short ligands in solution and then suspended at a high concentration in a solvent to form an ink. [8] In addition to this added cost, the toxicological properties, environmental impact, and end-of-life disposal of Pb-based PVs, including perovskites, is of critical importance and has received only minimal attention. [1] With this advancement the fabrication of the active layer is now more facile, however, the scalability of PbS QD solar cells is still uncertain.…”

Composite Structures with Emissive Quantum Dots for Light Enhancement

“…Finally, large‐scale and cost‐efficient production of robust QDs with precisely controlled optical properties, high photo and thermal stability, preprogrammed chemical compositions, and long shell life can catalyze fast future progress. This acceleration has already happened very recently in a wide range of general commercial applications, such as in the field of large TV and large panel displays with enhanced brightness and colored characteristics due to the embedded QD‐containing light sources and multicolored pixels …”

Commercializing colloidal quantum dot photovoltaics

“…The research group of Vladimir Bulović of the Massachusetts Institute of Technology finds that this approach of focusing solely on PCE might not be the most favorable route to commercialization of this technology. 5 They found that the CQD synthesis step currently limits production costs. They also found that the currently used hot-injection synthesis method is significantly capital-intensive, owing to low yields and therefore incompatible with industrial scale-up.…”

“…6 The heat-up method allows for high yields resulting in reduced synthesis costs down to USD$0.15/W from USD$0.51/W for the hot-injection method (compared to <USD$0.4/W for commercial silicon PV). 5 Additional encapsulant layers and balance-ofmodule components required for CQD PV, however, expectedly increase this number significantly. Jean et al 5 present guidelines to reduce CQD synthesis costs to as low as USD$0.05/W, including avoiding expensive precursors, deploying lowergrade precursors, and recycling solvents.…”

“…5 Additional encapsulant layers and balance-ofmodule components required for CQD PV, however, expectedly increase this number significantly. Jean et al 5 present guidelines to reduce CQD synthesis costs to as low as USD$0.05/W, including avoiding expensive precursors, deploying lowergrade precursors, and recycling solvents. The article also discusses the commercial prospects of CsPbI 3 CQDs, and the analysis suggests these to be significantly more expensive than PbS CQD PV.…”