Understanding and Minimizing VOC Losses in All Perovskite Tandem Photovoltaics

Understanding performance losses in all perovskite tandem photovoltaics is crucial to accelerate advancements toward commercialization, especially since these tandem devices generally underperform in comparison to what is expected from isolated layers and single junction devices. Here, the individual sub cells in all perovskite tandem stacks are selectively characterized to disentangle the various losses. It is found that non radiative losses in the high gap subcell dominate the overall recombination in the baseline system, as well as in the majority of literature reports. Through a multi faceted approach, the open circuit voltage VOC of the high gap perovskite subcell is enhanced by 120 mV. Employing a novel quasi lossless indium oxide interconnect, this enables all perovskite tandem solar cells with 2.00 V VOC and 23.7 stabilized efficiency. Reducing transport losses as well as imperfect energy alignments boosts efficiencies to 25.2 and 27.0 as identified via subcell selective electro and photo luminescence. Finally, it is shown how, having improved the VOC, improving the current density of the low gap absorber pushes efficiencies even further, reaching 25.9 efficiency stabilized, with an ultimate potential of 30.0 considering the bulk quality of both absorbers measured using photo luminescence. These insights not only show an optimization example but also a generalizable evidence based optimization strategy utilizing optoelectronic sub cell characterizatio

Large Grain Double Cation Perovskites with 18 mu s Lifetime and High Luminescence Yield for Efficient Inverted Perovskite Solar Cells

Recent advancements in perovskite solar cell performance were achieved by stabilizing the amp; 945; phase of FAPbI3 in nip type architectures. However, these advancements could not be directly translated to pin type devices. Here, we fabricated a high quality double cation perovskite MA0.07FA0.93PbI3 with low bandgap energy 1.54 eV using a two step approach on a standard polymer PTAA . The perovskite films exhibit large grains amp; 8764;1 amp; 956;m , high external photoluminescence quantum yields of 20 , and outstanding Shockley Read Hall carrier lifetimes of 18.2 amp; 956;s without further passivation. The exceptional optoelectronic quality of the neat material was translated into efficient pin type cells up to 22.5 with improved stability under illumination. The low gap cells stand out by their high fill factor amp; 8764;83 due to reduced charge transport losses and short circuit currents gt;24 mA cm 2. Using intensity dependent quasi Fermi level splitting measurements, we quantify an implied efficiency of 28.4 in the neat material, which can be realized by minimizing interfacial recombination and optical losse

Minimizing Interfacial Recombination in 1.8 eV Triple Halide Perovskites for 27.5 Efficient All Perovskite Tandems

All perovskite tandem solar cells show great potential to enable the highest performance at reasonable costs for a viable market entry in the near future. In particular, wide bandgap WBG perovskites with higher open circuit voltage VOC are essential to further improve the tandem solar cells performance. Here, a new 1.8 eV bandgap triple halide perovskite composition in conjunction with a piperazinium iodide PI surface treatment is developed. With structural analysis, it is found that the PI modifies the surface through a reduction of excess lead iodide in the perovskite and additionally penetrates the bulk. Constant light induced magneto transport measurements are applied to separately resolve charge carrier properties of electrons and holes. These measurements reveal a reduced deep trap state density, and improved steady state carrier lifetime factor 2.6 and diffusion lengths factor 1.6 . As a result, WBG PSCs achieve 1.36 V VOC, reaching 90 of the radiative limit. Combined with a 1.26 eV narrow bandgap NBG perovskite with a rubidium iodide additive, this enables a tandem cell with a certified scan efficiency of 27.