Thermal Evaporated Bismuth Triiodide (BiI3) Thin Films for Photovoltaic Applications
- PDF / 1,307,980 Bytes
- 4 Pages / 612.12 x 792.12 pts Page_size
- 58 Downloads / 179 Views
MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.405
Thermal Evaporated Bismuth Triiodide (BiI3) Thin Films for Photovoltaic Applications Natália F. Coutinho, Rafael B. Merlo, Nelson F. V. Borrero and Francisco C. Marques ‘Gleb Wataghin’ Institute of Physics, UNICAMP, 13083-859, Campinas-SP, Brazil
ABSTRACT
Bismuth triiodide (BiI3) is a potential candidate for application in solar cell due to its good optoelectronic properties and because it is free of toxic elements. It can be used as the absorber material in solar cells or converted into the perovskite-like material MA3Bi2I9, suitable also for photovoltaic applications. Bismuth triiodide has been prepared by physical vapour transport (PVT) and by solution process through spin coating. In this work we present optical and structural/topological properties of BiI3 deposited by thermal evaporation under high vacuum. The films are slightly tensile, polycrystalline, homogenously distributed and with good adherence on several substrates, with an indirect bandgap of 1.81 eV, index of refraction of 3.3 (630 nm), photoluminescence centered at 1.74 eV and a Raman peak at 118cm-1 associated with the Ag mode.
INTRODUCTION Currently, there has been a lot of effort in developing low-cost solar cells using semiconductors made with simple processes, in contrast to silicon, an expensive semiconductor, but used largely today in solar panels. Methylammonium lead halide perovskite, mainly the CH3NH3PbI3 structure (with inclusion of Cs, Sn and other elements) demonstrate incredible performance with high efficiency (22.1%) and reasonable stability [1]. However, the presence of the toxic element lead (Pb) in this material has been considered a barrier to the large scale use of this semiconductor due to environmental issues. Thus, different lead-free semiconductors have been proposed as potential candidates. Among those semiconductors, bismuth triiodide (BiI 3), a 1.67 eV bandgap semiconductor [2,3], has been used as active absorber layer in solar cells [2,4,5]. Alternatively, BiI3 has also been converted into a perovskite-like semiconductor MA3Bi2I9 and also used in solar cells [6-8]. Monocrystalline and polycrystalline BiI3 have been studied in X-ray detectors due to the high density of its elements [9-11]. Monocrystalline BiI3 is usually grown by the Bridgman method [12]. It is composed by 2D layers of BiI 6 octahedra, with the central Bi atom bonded to six iodine atoms. In addition to having a bandgap suitable for the solar spectrum (1.67eV) close to the bandgap value for maximum efficiency (1.45 eV) it also has high absorption coefficient (>105 cm -1) and high electron mobility 260 cm2/(V.s) [9,12], making it a promising candidate for solar cells. BiI3 thin films for solar cell application have been prepared by solution process [2,4,5] and physical vapor transport (PVT) [2]. Very little is known about their optoelectronic and structural properties. Films prepared by solution process deposited by spin coating technique on glass are polycrystalline with bandgap
Data Loading...
