The performance of CZTS solar cell, a promising candidate in the field of energy production from sunlight, can be improved by optimizing the parameters of most widely used CdS Buffer layer. In this work, numerical study have been done on the typical CZTS solar cell structures containing Mo thin film as back contact on glass substrate using SCAPS-1D solar cell simulation software. Then, the CZTS has been used as the absorber layer followed by CdS Buffer later. Following, ZnO and transparent conducting oxide n-ITO layers have been considered as window layer and front contact, respectively. In the simulations, the CdS Buffer layer has been doped with three different materials such as Silver (Ag), Copper (Cu) and Chlorine (Cl) for a wide acceptable range of carrier concentration. After obtaining the suitable carrier concentration, the thickness of the doped Buffer layer has been varied keeping other layer parameters constant to see the variation of performance parameters open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF) and efficiency (η, ) of the CZTS solar cell.

Here, the effect of lightly Niobium doped TiO2 layer on the performance of perovskite solar cells has been studied by using solar cell capacitance simulator (SCAPS). N addition, the effects of Niobium concentration, Buffer film thickness and operating temperature on the performance of the perovskite solar cell are investigated. For doping level of 3. 0 mol% into the TiO2 layer, cell efficiency of 18. 26% with Voc of 0. 96 V, Jsc of 22. 45 mA/ cm 2 and FF of 84. 25% has been achieved. Calculations show that thickness widening of Nb-doped TiO2 layer would decrease the efficiency and Voc of the cells. Increase in operating temperature from 300 k to 400 k would weaken the performance of the perovskite solar cell with both pure and Nb-doped TiO2 layers. However, the cell with Nb-doped TiO2 layer shows higher stability than the cell with pure TiO2 Buffer at higher temperatures.

Cadmium zinc sulfide (Cd1-xZnxS) as a wide-bandgap material with x=0. 7 was used in the present work as an alternative Buffer material to CdS to improve the efficiency o fZnO/Cd1-xZnxS/CdTe, ZnO/Cd1-xZnxS/CZTS and ZnO/Cd1-xZnxS/CZTSe thin film solar cells. The photovoltaic parameters such as efficiency, open circuit voltage (Voc), short circuit current density (Jsc), and the Fill Factor (FF) have been computed using one-dimensional simulation programs such as Solar Cell Capacitance Simulator (SCAPS v3. 3) and Analysis of Microelectronic and Photonic Structures (AMPS-1D). An improvement in conversion efficiency is noticed compared to the structure with the CdS Buffer layer. It is found that the efficiencies of Cd1-xZnxS/CZTSe and Cd1-xZnxS/CdTeareincreased from 12. 61% to 15. 35% and from 17. 53% to 18. 83%, respectively. The simulations were performed for 1 μ, mthick absorber layers. It is also found that efficiency rises from 12. 53% to 13. 23% with Cd1-xZnxS/CZTS structure for CZTS thickness of 2. 5 μ, m. Moreover, the Quantum Efficiency (QE) characteristics display a maximum value of more than 80% in the visible range and the structures presented a slight improvement in the short wavelength. The present study shows that the suggested structures with aCd1-xZnxS Buffer layer may improve efficiency and reduce the amount of Cd, which is a toxic element.

Single-walled carbon nano tube (SWCNT) is used as a Buffer layer to improve the performance of polymer solar cells. The Buffer layer is located between the active layer and the cathode electrode in the solar cell structure such as PET/ITO/PEDOT: PSS/MEH-PPV: C60 (1: 2) /SWCNT/Al. SWCNTs act as tunnels to help electron collection by cathode electrode, prevent the randomly movement of electrons, leading to the reduction of recombination at the interfaces after dissociation. By implementing this method, the short circuit current (Jsc) of fabricated solar cells increases from 20% to 40% depending on the solvent and the open circuit voltage (Voc) reduces slightly. Since the type of solvent has an important effect on the properties of fabricated solar cells, the active layer was spin coated using three different solvents which were Chlorobenzene, 1, 2-Dichlorobenzene and Toluene. The best performance was achieved for the device fabricated using Chlorobenzene. The resulted output powers using Chlorobenzene, 1, 2-Dichlorobenzene and Toluene were 10.04 mW/cm2, 7.59 mW/cm2 and 1.74 mW/cm2 respectively.

Cu (In, Ga) Se2 thin films (CIGS) on metallic substrate (titanium, molybdenum, aluminum, stainless steel) were prepared by a two-step selenization of Co-evaporated metallic precursors in Se-containing environment under N2 gas flow. Structural properties of prepared thin film were studied. To characterize the optical quality and intrinsic defect nature low-temperature photoluminescence, were performed. Results shows that the structural and optical properties of Cu (In, Ga) Se2 thin films strongly depend on the growth condition, charactristics of substrate and chemical composition. In2S3 thin layer has been used as Buffer layer in CIGS solar cells and physical properties of them investigated. Solar cells were completed by vacuum deposition of ZnO/ZnO: Al layers and Ni/Al contact fingers. The surface morphology and bulk composition of thin films were investigated by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The optical testing was carried out by recording transmittance spectra of the samples by spectrophotometers in the spectral range 190–3000 nm at a resolution of 1 nm. The better conversion efficiencies were around 12.0 %.

The improvement of the physical properties of Indium Tin Oxide (ITO) layers is quite advantageous in photovoltaic applications. In this study the ITO film is deposited by RF sputtering onto p-type crystalline silicon (c-Si) with (100) orientation, multicrystalline silicon (mc-Si), and glass substrates coated with ZnO and annealed in vacuum furnace at 400°C. Electrical, optical, structural and morphological properties of the ITO films were analyzed by four point probe, UV/VIS/IR spectrophotometer, X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The quality of films deposited on Buffer layer is found to be superior to those grown directly on a substrate. The structural, optical and electrical studies reveal that ZnO Buffer layers improve the crystalline quality, optical and electrical properties of ITO thin films.