Effect of RF Power on the Physical Properties of Sputtered ZnSe Nanostructured Thin Films for Photovoltaic Applications

Abstract

Zinc selenide (ZnSe) thin films were deposited by RF magnetron sputtering in specific conditions, onto optical glass substrates, at different RF plasma power. The prepared ZnSe layers were afterwards subjected to a series of structural, morphological, optical and electrical characterizations. The obtained results pointed out the optimal sputtering conditions to obtain ZnSe films of excellent quality, especially in terms of better optical properties, lower superficial roughness, reduced micro-strain and a band gap value closer to the one reported for the ZnSe bulk semiconducting material. Electrical characterization were afterwards carried out by measuring the current–voltage (I-V) characteristics at room temperature, of prepared “sandwich”-like Au/ZnSe/Au structures. The analysis of I-V characteristics have shown that at low injection levels there is an Ohmic conduction, followed at high injection levels, after a well-defined transition voltage, by a Space Charge Limited Current (SCLC) in the presence of an exponential trap distribution in the band gap of the ZnSe thin films. The results obtained from all the characterization techniques presented, demonstrated thus the potential of ZnSe thin films sputtered under optimized RF plasma conditions, to be used as alternative environmentally-friendly Cd-free window layers within photovoltaic cells manufacturing.

An overview on the role of ZnTe as an efficient interface in CdTe thin film solar cells: a review

“…112 On annealing at 230 1C, they showed a sharp fall in transmittance at the band edge, which verified the good crystallinity of the films with a wide band gap of 2.29 eV. 124 The pristine thin films showed a lower band gap of 1.9 eV compared to the annealed films (2.25 eV) at 350 1C, where excess unbound Te was absent for the annealed films. 196 The substrate temperature also affects the optical energy band gap of ZnTe thin films.…”

“…127 The topography of the ZnTe films with a thickness in the range of 120–600 nm thickness was revealed to exhibit an increased average roughness from 6.7 nm to 33.7 nm and root mean square (RMS) roughness from 8.27 nm to 44.2 nm. 124 For MBE grown ZnTe:N thin films, the surface root mean square roughness was found to increase with growth temperature. 132 Hence, surface topographies and statistical parameters of films were greatly influenced by the different pre- and post-treatments as well as the deposition conditions.…”

“…123 The films grown by the thermal evaporation technique demonstrated good uniformity and quality, and thus this method can be widely used for the formation of contacts in all types of devices including solar cells and sensors. Pristine films could be subjected to local thermal treatment inside the deposition chamber to get better-quality films [124][125][126] in accordance with the device architecture. The parameters obtained thus far employing this method are depicted in Table 2.…”

FROM Si NANOWIRES TO Ge NANOCRYSTALS FOR VIS-NIR-SWIR SENSORS AND NON-VOLATILE MEMORIES: A REVIEW

“…Group IV semiconductors are intensively investigated [1][2][3][4] along with group III-V [5,6], II-VI [7][8][9][10][11][12][13][14][15][16][17] and IV-VI semiconductors [18,19].…”

Advances in Nanomaterials for Photovoltaic Applications

“…According to the authors, the ALD process could be also advantageously engaged into the large-scale mass production of CIGS-based solar cells. In contrast, other researchers demonstrated that zinc selenide (ZnSe) thin films prepared by radio-frequency (RF) magnetron sputtering under optimized specific conditions could possess excellent physical properties to successfully act as environmentally-friendly “window” materials for solar cells, helping thus at diminishing the amount of cadmium (Cd) still commonly used for the second generation of solar cells relying on cadmium telluride (CdTe) as main absorber [ 7 ].…”