Understanding the sub-band gap luminescence in Ruddlesden-Popper 2D metal halide hybrid perovskites (2D HaPs) is essential for efficient charge injection and collection in optoelectronic devices. Still, its origins are still under debate with respect to the role of self-trapped excitons or radiative recombination via defect states. In this study, we characterized charge separation, recombination, and transport in single crystals, exfoliated layers, and polycrystalline thin films of butylammonium lead iodide (BAPbI), one of the most prominent 2D HaPs.
View Article and Find Full Text PDFImproved stability and efficiency of two-terminal monolithic perovskite-silicon tandem solar cells will require reductions in recombination losses. By combining a triple-halide perovskite (1.68 electron volt bandgap) with a piperazinium iodide interfacial modification, we improved the band alignment, reduced nonradiative recombination losses, and enhanced charge extraction at the electron-selective contact.
View Article and Find Full Text PDFUsing advanced near-UV photoemission spectroscopy (PES) in constant final state mode (CFSYS) with a very high dynamic range, we investigate the triple-cation lead halide perovskite Cs(MAFA)Pb(IBr) and gain detailed insights into the density of occupied states (DOS) in the valence band and band gap. A valence band model is established which includes the parabolic valence band edge and an exponentially decaying band tail in a single equation. This allows us to precisely determine two valence band maxima (VBM) at different -vectors in the angle-integrated spectra, where the highest one, resulting from the VBM at the -point in the Brillouin zone, is found between -1.
View Article and Find Full Text PDFTandem solar cells that pair silicon with a metal halide perovskite are a promising option for surpassing the single-cell efficiency limit. We report a monolithic perovskite/silicon tandem with a certified power conversion efficiency of 29.15%.
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