Design considerations for the bottom cell in perovskite/silicon tandems: a terawatt scalability perspective
Abstract:
Perovskite/silicon tandems have smashed through the 30% efficiency barrier, which represents a promising step towards high efficiency solar modules. However, the processing used to fabricate high efficiency devices is not compatible with mass production. For this technology to be impactful in the urgent fight against climate change and be scalable to the multi-terawatt (TW) level, a shift in mindset is required when designing the silicon bottom cell. In this work, we outline the design requirements for the silicon cell, with a particular focus on the constraints imposed by industrial processing. In doing so, we discuss the type of silicon wafers used, the surface treatment, the most appropriate silicon cell architecture and the formation of metal contacts. Additionally, we frame this discussion in the context of multi-TW markets, which impose additional constraints on the processing relating to the sustainability of the materials used. The discussion herein will help to shape the design of future silicon solar cells for use in tandems, so that the LCOE of solar electricity can be driven to new lows.Thermal management enables stable perovskite nanocrystal light-emitting diodes with novel hole transport material
Abstract:
The severely insufficient operational lifetime of perovskite light-emitting diodes (LEDs) is incompatible with the rapidly increasing external quantum efficiency, even as it approaches the theoretical limit, thereby significantly impeding the commercialization of perovskite LEDs. In addition, Joule heating induces ion migration and surface defects, degrades the photoluminescence quantum yield and other optoelectronic properties of perovskite films, and induces the crystallization of charge transport layers with low glass transition temperatures, resulting in LED degradation under continuous operation. Here, a novel thermally crosslinked hole transport material, poly(FCA<sub>60</sub> -co-BFCA<sub>20</sub> -co-VFCA<sub>20</sub> ) (poly-FBV), with temperature-dependent hole mobility is designed, which is advantageous for balancing the charge injection of the LEDs and limiting the generation of Joule heating. The optimised CsPbI<sub>3</sub> perovskite nanocrystal LEDs with poly-FBV realise approximately a 2-fold external quantum efficiency increase over the LED with commercial hole transport layer poly(4-butyl-phenyl-diphenyl-amine) (poly-TPD), owing to the balanced carrier injection and suppressed exciton quenching. Moreover, because of the Joule heating control provided by the novel crosslinked hole transport material, the LED utilising crosslinked poly-FBV has a 150-fold longer operating lifetime (490 min) than that utilizing poly-TPD (3.3 min). The study opens a new avenue for the use of PNC LEDs in commercial semiconductor optoelectronic devices.Chloride-Based Additive Engineering for Efficient and Stable Wide-Bandgap Perovskite Solar Cells.
Abstract:
Metal halide perovskite based tandem solar cells are promising to achieve power conversion efficiency beyond the theoretical limit of their single-junction counterparts. However, overcoming the significant open-circuit voltage deficit present in wide-bandgap perovskite solar cells remains a major hurdle for realizing efficient and stable perovskite tandem cells. Here, a holistic approach to overcoming challenges in 1.8 eV perovskite solar cells is reported by engineering the perovskite crystallization pathway by means of chloride additives. In conjunction with employing a self-assembled monolayer as the hole-transport layer, an open-circuit voltage of 1.25 V and a power conversion efficiency of 17.0% are achieved. The key role of methylammonium chloride addition is elucidated in facilitating the growth of a chloride-rich intermediate phase that directs crystallization of the desired cubic perovskite phase and induces more effective halide homogenization. The as-formed 1.8 eV perovskite demonstrates suppressed halide segregation and improved optoelectronic properties.Photovoltaic performance of FAPbI3 perovskite is hampered by intrinsic quantum confinement
Abstract:
Formamidinium lead trioiodide (FAPbI3) is a promising perovskite for single-junction solar cells. However, FAPbI3 is metastable at room temperature and can cause intrinsic quantum confinement effects apparent through a series of above-bandgap absorption peaks. Here, we explore three common solution-based film-fabrication methods, neat N,N-dimethylformamide (DMF)–dimethyl sulfoxide (DMSO) solvent, DMF-DMSO with methylammonium chloride, and a sequential deposition approach. The latter two offer enhanced nucleation and crystallization control and suppress such quantum confinement effects. We show that elimination of these absorption features yields increased power conversion efficiencies (PCEs) and short-circuit currents, suggesting that quantum confinement hinders charge extraction. A meta-analysis of literature reports, covering 244 articles and 825 photovoltaic devices incorporating FAPbI3 films corroborates our findings, indicating that PCEs rarely exceed a 20% threshold when such absorption features are present. Accordingly, ensuring the absence of these absorption features should be the first assessment when designing fabrication approaches for high-efficiency FAPbI3 solar cells.