In recent years, the power conversion efficiency (PCE) of perovskite solar cells has increased rapidly with recent studies reporting PCE over 20% in laboratory studies. However, lifetimes for these devices are counted in hundreds to a small number of thousands of hours e.g. 2000 hours with a PCE of 23.5% . This equates to less than 3-months – well short of requirements for most practical applications. Moreover, these levels of efficiency and durability have been achieved without a focus on cost and manufacturability. There is a trade-off between stability, lifetime and cost.
Our target in SUNREY is to achieve an efficiency of at least 25% together with a lifetime of 25 years. This matches the efficiency of the best reported perovskite solar cells but with a more than 100X in lifetime and 25X longer lifetime than best reported stable perovskite cells. This will be achieved using high efficiency Pb-based perovskites with the lifetime boosted by improved intrinsic stability conferred by new charge transport layers, 2-D perovskite absorbers and optimised process conditions developed in the project together with new barrier materials and improved encapsulation strategies.
The main environmental concern with perovskite technologies is because the perovskite absorber materials contain lead (Pb) and this can create hazards in recycling and waste stream management or be released into the environment where it is toxic and bioaccumulative. Improved lifetime compared to current state of the art perovskite reduces the quantity of devices and materials that enter the environment or waste streams, in this case 25X less Pb.
Moreover, the advanced encapsulation and barrier materials will reduce the rate of any Pb leakage into the environment in the case of lost or discarded units.
The best solution to the problem of Pb content in perovskite PV cells is to remove the Pb altogether. However, current Pb-free perovskites suffer from lower efficiency and poorer stability than their Pb-based counterparts with the highest power conversion efficiencies now being in the region of 14% but lifetime of around 100 hours. SUNREY will focus on boosting the lifetime of Sn-based perovskites into thousands of hours for lifetimes approaching years, opening up possibilities for commercial use of Pb-free perovskites in specific applications such as disposable, portable IoT devices used in digital farming or relatively benign indoor applications where degradation is slower.
The sustainability of SUNREY will also be addressed in the manufacturing processes with a focus on low-temperature solution-based processes and materials compatible with these processes such as a novel organic electron transport layer. These will be quantified in SUNREY through detailed lifecycle and sustainability analyses including analysis of all critical materials and lifecycle costs. These data will be used to demonstrate to society and investors the benefits of SUNREY technology over existing photovoltaic systems.
