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Photovoltaics
Published in Sheila Devasahayam, Kim Dowling, Manoj K. Mahapatra, Sustainability in the Mineral and Energy Sectors, 2016
Venkata Manthina, Alexander Agrios, Shahzada Ahmad
Concerns regarding the toxicity of cadmium in CdTe and the use of rare elements in both CdTe and CIGS has motivated research toward thin-film PV based entirely on sustainable materials. In CIGS, both indium and selenium are of low earth abundance. The indium can be replaced with zinc, if the gallium is also replaced with tin. Replacing selenium with sulfur then gives rise to copper zinc tin sulfide (CZTS), a material comprising exclusively nontoxic, abundant, and cheap elements. Owing to the toxicity of cadmium and limited reserves of indium and tellurium used in CdTe and CIGS solar cells, the search for alternative materials for thin-film solar cells started. CZTS was developed with nontoxic and earth-abundant materials. CZTS is an excellent absorber because of its ideal band gap of 1.45 eV and high absorption coefficient (1 × 104 cm−1) in the visible wavelength range (Ito and Nakazawa, 1988). CZTS solar cells were fabricated using CZTS p-type absorber and CdS n-type layer. Aluminum-doped zinc oxide (AZO) and tin-doped indium oxides (ITO) are used as transparent conducting oxide (TCO) layers (Yang et al., 2008; Ding et al., 2013). Silver/chromium is used as a finger electrode.
Solar Markets in the 21st Century
Published in Anco S. Blazev, Solar Technologies for the 21st Century, 2021
The future is looking bright for many PV technologies, but some significant changes are expected and needed to bring them to LCOE, and full utilization. Some causes of disruptive change will be: Direct solidification of silicon material provides the cheapest wafers. Direct solidification of molten Si offers true kerfless wafering (which eliminates losses from sawing). It is the Holy Grail for the solar industry, which has been the goal of many companies since the 1970s. This technology has a potential market size of up to $600 million, and is expected to be the first to reach full commercialization by 2015.Alternatives to increased cell efficiency, such as optimized anti-reflective and light-trapping coatings. These are also 2nd-tier technologies, looking at a market size of over $600 million. By providing active competition, they will pave the way to cost-effective efficiency gains. Commercialization of the new technologies is expected most likely around 2015 and beyond.New active thin film layers. New processes and materials are expected to dominate the 21st century PV technological gains, such as: Copper-zinc-tin-sulfide (CZTS) cell technology to replace some of the competing thin film technologies (possibly CIGS and CdTe) and gain significant market share through use of cheaper, safer materials, with the major advantage of eliminating the use of exotic, expensive and toxic materials, such as indium, gallium, cadmium.Epitaxial Si (epi-Si) technology, and variations of, have the potential to replace amorphous silicon (a-Si) infrastructure and reach higher efficiencies at lower cost than present-day a-Si modules.
Chemical Route Synthesis and Properties of CZTS Nanocrystals for Sustainable Photovoltaics
Published in Vidya Nand Singh, Chemical Methods for Processing Nanomaterials, 2021
Shefali Jain, Pooja Semalti, Vidya Nand Singh, Shailesh Narain Sharma
Photovoltaic electricity generation based on silicon technology with a record efficiency of 25% does not fulfill the energy demands of the earth [9]. To overcome the high cost of silicon wafers, the materials such as CdSe, CdTe, CuInSe2, CuInGa(SSe)2 , CIGS offering stable and efficient (— 22%) [9] photovoltaic modules (second generation photovoltaic materials) have been studied. However, the availability and expensiveness of indium is also one of the concerns. To meet the increased demands of energy, the major issues, such as increasing the use of the traditionally available materials, using cost effective methods, and searching for other alternatives for both the materials and cost-effective methods maintaining the eco-friendly environments need to be addressed. Hence, it is necessary to develop the solar cell with high efficiency, long term stability, less environmental damaging, and lowest possible cost. The quaternary compounds, such as Cu2ZnSnS4 (CZTS), Cu2ZnSnSe4 (CZTSe), and Cu2ZnSn(SexS1)4 (CZTSSe) have attracted escalating consideration of researchers for photovoltaic devices [10]. They have very good properties, such as P-type conductivity, ideal direct bandgap, and large absorption coefficient for photoactive applications. Among these, the CZTS absorber layer is of immense importance because of its direct and low band gap of 1.4-1.5 eV with a higher absorption coefficient of 10 cm-1 [11]. The availability of the constituent elements of these particles is — 50, 75, 2.2, and 260 ppm, respectively, as compared to indium, which is — 0.049 ppm only [12]. Due to the toxic constituents, such as Cd and low abundance of In and Te, these quaternary chalcopyrite materials act as an absorber layer by replacing half with tin and half with zinc. Therefore, CZTS compound has been studied as a new developing absorber material in inorganic, low-cost solar cell devices.
Optimization of sulphurization temperature for the production of single-phase CZTS kesterite layers synthesized by electrodeposition
Published in Surface Engineering, 2020
R. Boudaira, O. Meglali, A. Bouraiou, N. Attaf, C. Sedrati, M.S. Aida
Copper zinc tin sulphide (CZTS) belongs to the group of I2–II–IV–VI4 quaternary semiconductors and it is a promising alternative to current absorber layer materials CdTe, CIS and CIGS since their elemental components are cheap, non-toxic and abundant in the earth’s crust [1,2]. The abundance in the earth of the CZTS components is between 2.2 and 260 ppm while the amount of the indium is only 0.05 ppm [3]. Owing to the direct band gap energy in the range 1.4–1.56 eV that matches well with the solar spectrum [4], the large absorption coefficient , the intrinsic p-type electrical conductivity and low thermal conductivity [5], CZTS is considered as one of the potential absorber materials for the next-generation solar cells. Thin films solar cells based on chalcogenide material Cu(In,Ga)Se2 achieved a high efficiency beyond 22% [6] while for CZTS solar cells the maximum reported efficiency was 12.6% by non-vacuum deposition method [7] and 11.6% by vacuum method [8]. The low performance of CZTS solar cells is due to the low open-circuit voltage (Voc) [9] and the formation of secondary phases in the CZTS absorber layer. So, one of the challenges in the synthesis of CZTS is how to identify, control and remove these secondary phases in order to reach higher conversion efficiencies.
Preparation and characterization of Cu2ZnSnS4 thin films by two-stage process
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Nagamalleswari D., Kishore Kumar Y.B., Kiran Y.B., Suresh Babu G.
The sharp decrease of the transmittance near the fundamental absorption edge indicates that the optical transition is direct. The nature of the optical transitions is calculated using the standard relation αhν = A(hν − Eg)n/hν, where A is constant, h is Planck’s constant, ν is frequency of the incident beam, and exponent n = 1/2, 3/2, 2 based on whether the optical transition is direct allowed, direct-forbidden, indirect-allowed, respectively (Pankove 1975). In the present analysis, the equation is satisfied for n = 1/2 indicating that the optical transition is direct-allowed in nature. The Tauc plot of CZTS thin films annealed at 763 K is shown in Figure 8. The optical bandgap of CZTS films is found to be 1.48 eV, which is close to the reported bandgap of CZTS film (Courel et al. 2017b; Rajeshmona et al. 2011). Films annealed at 763 K being Zn-rich, indicating zinc sulfide might be present in the film. However, ZnS presence could not be identified below 550 nm region in transmission spectrum after strong absorption by CZTS phase. The bandgap of CZTS thin films annealed at 733 K is found to be 1.1 and 1.5 eV. The former is attributed to bandgap of CTS (Guo et al. 2016) and latter is attributed to direct optical bandgap of CZTS films. The spectral transmittance (T) of a spray deposited ZnS film is shown in Figure 9. The bandgap of spray deposited ZnS film was found to be 3.52 eV (López et al. 2005). The relative uncertainty in the determination of the bandgap is ±0.02 eV.
Thermally evaporated CZTSe thin films for solar cell application: Study on the effect of annealing time
Published in Particulate Science and Technology, 2020
J. Henry, K. Mohanraj, G. Sivakumar
The photo I-V plot of CZTSe thin films annealed at 300°C for 2 h, 4 h and 6 h are shown in Figure 10. The plot recorded under visible light shows higher photo current than that of the dark condition. This is due to the production of electron hole pairs under irradiation, the light excites electrons in the valance band to the conduction band and then holes in the CZTSe thin film increase. The photosensitivity of the film can be calculated according to the formula (Sadekar, Ghule, and Sharma 2015)where S is photosensitivity, Idark is dark current and Ilight is current generated under illumination. The photosensitivity is found to be 70, 73, and 140% for the films annealed at 300°C for 2, 4, and 6 h, respectively. The enhancement of photosensitivity is attributed to the improvement of crystalline properties with increasing in annealing time which leading to the reduction of the structural like strain etc (Ibraheam et al. 2017). CZTSe is known to be typically p-type. Light irradiation excites electrons in the valence band to the conduction band and then increases the holes in them. As a result, the current is increased obviously and the conductivity of the film is enhanced. This obvious photoresponsive behavior indicates the potential use CZTSe thin films in solar energy conversion systems, such as the fabrication of photovoltaic devices (Shi et al. 2013). The obtained photocurrent value is compared with earlier reports and are presented in Table 2. By comparing our results (Table 2) with earlier reports, it can be inferred that the present study shows high values for photocurrent