SummaryMaterials to be used in the space environment have to withstand extreme conditions, particularly with respect to cosmic particle irradiation. We report robust stability and high tolerance of organolead trihalide perovskite solar cells against high-fluence electron and proton beams. We found that methylammonium and formamidinium-based lead iodide perovskite solar cells composed of TiO2 and a conductive polymer, as electron and hole transport materials, can survive against accumulated dose levels up to 1016 and 1015particles/cm2 of electrons (1 MeV) and protons (50 KeV), respectively, which are known to completely destroy crystalline Si-, GaAS-, and InGaP/GaAs-based solar cells in spacecraft. These results justify the superior tolerance of perovskite photovoltaic materials to severe space radiations and their usefulness in satellite missions.
The conversion efficiency of InGaP/(In)GaAs/Ge -based multijunction solar cells has been improved up to 29-30% (AM0) and 31-32% (AM1Á5G) by technologies, such as double-hetero wide band-gap tunnel junctions, combination with Ge bottom cell with the InGaP first hetero-growth layer, and precise lattice-matching to Ge substrate by adding 1% indium to the conventional GaAs lattice-match structure. Employing a 1Á95 eV AlInGaP top cell should improve efficiency further. For space use, radiation resistance has been improved by technologies such as introducing of an electric field in the base layer of the lowest-resistance middle cell, and EOL current matching of sub-cells to the highest-resistance top cell. A grid structure and cell size have been designed for concentrator applications in order to reduce the energy loss due to series resistance, and 38% (AM1Á5G, 100-500 suns) efficiency has been demonstrated. Furthermore, thin-film structure which is InGaP/GaAs dual junction cell on metal film has been newly developed. The thin-film cell demonstrated high flexibility, lightweight, high efficiency of over 25% (AM0) and high radiation resistance.
World-wide studies on multi-junction (tandem) solar cells have led to record-breaking improvements in conversion efficiencies year after year. To obtain detailed and proper feedback for solar-cell design and fabrication, it is necessary to establish standard methods for diagnosing subcells in fabricated tandem devices. Here, we propose a potential standard method to quantify the detailed subcell properties of multi-junction solar cells based on absolute measurements of electroluminescence (EL) external quantum efficiency in addition to the conventional solar-cell external-quantum-efficiency measurements. We demonstrate that the absolute-EL-quantum-efficiency measurements provide I–V relations of individual subcells without the need for referencing measured I–V data, which is in stark contrast to previous works. Moreover, our measurements quantify the absolute rates of junction loss, non-radiative loss, radiative loss, and luminescence coupling in the subcells, which constitute the “balance sheets” of tandem solar cells.
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