Single Step Electrochemical Deposition of p-Type Undoped and Co²⁺Doped FeS₂Thin Films and Performance in Heterojunction Solid Solar Cells

Abstract

Undoped and Co 2+ doped FeS 2 thin films (Co compositions are 1 to 5 mole%) were deposited on indium tin oxide glass substrate by a single step electrochemical deposition (ECD) method at low temperature (70 • C). Glancing angle X-ray diffraction (GAXRD) and Raman spectra showed that as-deposited undoped and Co 2+ doped FeS 2 thin films have a cubic pyrite structure without any trace of orthorhombic marcasite phase. Co 2+ doping does not affect the cubic structure of FeS 2 thin films with a strong (111) plane preferred orientation in all the doped thin films. The height profiling of 3 mole% of Co 2+ doped FeS 2 thin film by atomic force microscopy revealed a smooth surface with uniform distribution of particles and low roughness values. Co 2+ (3, 4 and 5 mole%) doped thin films show a strong absorption peak in the higher wavelength region. Magnetic measurement reveals that Co 2+ doping into the FeS 2 lattice induces ferromagnetism. The Co 2+ in FeS 2 thin films acts as the acceptor and the original p-type conductivity is retained. Solar light irradiation with the intensity of 100 mW/cm 2 on Co 2+ (3 mole%) doped FeS 2 thin film cell resulted in a power conversion efficiency of 5.42%.

Origin of Ferromagnetism in Pure and Ion Doped Pyrite FeS2 Nanoparticles

“…A further growth leads to a maximum at x = 0.3 and afterwards to a decrease. For large Co concentration the micro‐strain decreases and the NP behaves as undoped material . A similar behavior of M is observed in ref.…”

“…This difference gives rise to a tensile strain. Prabukanthan et al have reported that the lattice parameter in Co doped FeS 2 thin films grows up with increasing Co doping and then drops down. From here we conclude that the micro‐strain increases at first and after it decreases.…”

“…Due to sulfur vacancies at the surface of the nanocrystalline material one observes a saturation magnetization, remanent magnetization and coercivity field . Magnetic measurement reveals that Co 2+ doping into FeS 2 thin films induces ferromagnetism …”

“…Ferromagnetism can be even caused by doping of bulk FeS 2 with different transition metal ions. Tian et al have reported ferromagnetism in Co and other transition metal doped marcasite FeS 2 , respectively, whereas Prabukanthan et al have considered the magnetic properties of Co 2+ doped pyrite FeS 2 thin films. Notice that bulk CoS 2 is a weak ferromagnet with K …”

Vapor transport deposition of antimony selenide thin film solar cells with 7.6% efficiency

“…Overall, all these advantages facilitated the fabrication of high-quality Sb 2 Se 3 films, leading to increased V OC , J SC as well as FF (VTD: 0.42 V, 29.9 mA cm −2 , 60.4% vs. RTE: 0.39 V, 25.3 mA cm −2 , 56.4%). The champion device achieved the efficiency record 7.6%, much higher than SnS, Cu 2 O and FeS 2 solar cells which have been studied for many years 47–49 . The fabrication of record efficiency Sb 2 Se 3 solar cells employing vapor transport deposition, a technique with proven high turnaround and low cost for commercial CdTe solar cells, further strengthens the great potential of our Sb 2 Se 3 thin film photovoltaics.…”