Progress on lead-free metal halide perovskites for photovoltaic applications: a review

ABSTRACT: Metal halide perovskites have revolutionized the field of solution-processable photovoltaics. Within just a few years, the power conversion efficiencies of perovskite-based solar cells have been improved significantly to over 20%, which makes them now already comparably efficient to silicon-based photovoltaics. This breakthrough in solution-based photovoltaics, however, has the drawback that these high efficiencies can only be obtained with lead-based perovskites and this will arguably be a substantial hurdle for various applications of perovskite-based photovoltaics and their acceptance in society, even though the amounts of lead in the solar cells are low. This fact opened up a new research field on lead-free metal halide perovskites, which is currently remarkably vivid. We took this as incentive to review this emerging research field and discuss possible alternative elements to replace lead in metal halide perovskites and the properties of the corresponding perovskite materials based on recent theoretical and experimental studies. Up to now, tin-based perovskites turned out to be most promising in terms of power conversion efficiency; however, also the toxicity of these tin-based perovskites is argued. In the focus of the research community are other elements as well including germanium, copper, antimony, or bismuth, and the corresponding perovskite compounds are already showing promising properties. GRAPHICAL ABSTRACT: [Image: see text

Recrystallization and phase stability study of cesium tin iodide for application as a hole transporter in dye sensitized solar cells

In this work, we report synthesis and stability analysis of cesium tin iodide (CsSnI3) prepared through solid state and solution route methods for its application as a hole transport layer in dye sensitized solar cells (DSSC). Phase formation, chemical stability and degradation mechanism of CsSnI3 were studied using X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and Raman spectroscopy. Optical band gap of the material was studied using UV-vis spectroscopy and photoluminescence studies. CsSnI3 synthesized through solid state route was used as a hole transport material (HTM) for dye sensitized solar cells with cell efficiency up to 3%. Temperature dependent excitonic emission studies shows that B-gamma-CsSnI3 shows a linear increase in band gap with increasing temperature. (C) 2015 Elsevier Ltd. All rights reserved

Lead free, air stable perovskite derivative Cs2SnI6 as HTM in DSSCs employing TiO2 nanotubes as photoanode

Cs2SnI6 is an air-stable and non-toxic perovskite variant photovoltaic material which exhibits p-type conductivity under doped conditions. In this work, we report the synthesis and stability studies of Cs2SnI6 towards its application as a solid-state Hole Transport Material (HTM) in Titania Nanotube (TNT) based Dye Sensitized Solar Cells (DSSCs). Cs2SnI6 crystals were synthesized using precipitation method and its stability was assessed using X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Thermogravimetric Analysis (TGA). Cs2SnI6 doped with SnI2 was deposited onto the TNT photo-anode as the HTM layer through dip coating. Deposition time was varied to obtain a continuous layer of Cs2SnI6 HTM over TNT photo-anode and cell characteristics were studied. We were able to fabricate air stable, all solid-state solar cells with a Jsc of 6 mA/cm(2), Voc of 536 mV and PCE of 1.3%. The study propounds contemporary analysis on Sn based perovskite systems, in the field of DSSCs