Tianyue Li

Bismuth (Bi) based solar cells have recently attracted significant attention in line with lead-free perovskite solar cells development. In this study, 2-aminothiazolium iodide (ATI) is used to prepare highly crystalline and environmentally stable lead free ATBiI₄ photoactive thin films, which were comprehensively characterized for integration into planar solar cells with the n–i–p device architecture. The ATBiI₄ solar cells delivered a power conversion efficiency of 0.53% with open-circuit voltage of 0.83 V under 1 sun, a 12.8% increase in the power conversion efficiency arising mainly due to 124% increase in the open circuit voltage as compared to the triple mesoscopic devices explored previously. Furthermore, in this study the solar cells have been explored for harvesting energy from indoor white light emitting diodes (LED) for the first time revealing a power output of 81.75 μW cm⁻² at 500 lux. As ATBiI₄ has its absorption maximum in the ultra-violet wavelength region, the solar cells have been further tested under 9 W UV LED (395–400 nm), which yielded a power output of 8.07 μW cm⁻² at 150 lux. This work demonstrates that 2-aminothiazolium bismuth iodide solar cells are promising microwatt energy sources which can find potential application for powering smart electronics.

We demonstrate a novel synthetic route to films of a bismuth chalcohalide, Bi₁₃S₁₈I₂, and investigate its potential as the active electrode material in EDLC-type supercapacitors.

We report on the synthesis, crystal structures, optoelectronic properties and solar cell device studies of three novel organic–inorganic iodobismuthates – [C₃H₄NS]₃[Bi₂I₉] ([TH]₃[Bi₂I₉]), [C₃H₄N₂]₃[Bi₂I₉] ([IM]₃[Bi₂I₉]) and [C₃H₅N₂S][BiI₄] ([AT][BiI₄]) as lead-free light harvesters. [TH]₃[Bi₂I₉] and [IM]₃[Bi₂I₉] show zero-dimensional structures, whereas a one-dimensional edge-sharing chain structure of BiI₆-octahedra was observed in [AT][BiI₄], with interchain short I⋯I contacts also giving rise to the possibility of three-dimensional charge transport ability. Accordingly, greater energy dispersion in the band structure of [AT][BiI₄] can be observed, and less contribution from the organic moities at the conduction band minimum in [AT][BiI₄] than [TH]₃[Bi₂I₉] have been confirmed by density functional theory calculations. Moreover, bandgap values are redshifted from 2.08 eV for [TH]₃[Bi₂I₉] and 2.00 eV for [IM]₃[Bi₂I₉] to 1.78 eV for [AT][BiI₄], determined by UV-Vis reflectance spectroscopy. Power conversion efficiency of 0.47% has been achieved by using ([AT][BiI₄]) as the light absorber in a hole-conductor-free, fully printable solar cell, with relatively good reproducibility. We also note the observation of a capacitance effect for the first time in a photovoltaic device with bismuth-based solar absorber, which may be related to the mesoporous carbon counter-electrode.

X-ray diffraction, electronic characterisation and mesoscopic solar cell evaluation were performed for two novel iodobismuthates, C₅H₆NBiI₄([py][BiI4]) and C₆H₈NBiI₄([mepy][BiI4]).