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The present work focuses on studying the optical properties of the pristine PEDOT:PSS and the PEDOT:PSS modified with de-ionized water, ethylene glycol and MWCNT. The effect of various additives on the absorption, the refractive index, and the dielectric constant has been inspected. The refractive index dispersion has been analyzed using the single oscillator model developed by Wemple and DiDomenico. The optical constants, such as the dispersion energy, the single oscillator energy, the average oscillator strength, the average interband oscillator strength, the long wavelength refractive index, and the plasma resonance frequency have been determined. The energy bandgap was found reduced with the addition of EG and MWCNT representing a red shift and a conformational change in the PEDOT:PSS from a benzoid to a quinoid structure. The UV-visible absorption spectrum indicates the creation of free charges. The increase in the refractive index with doping suggests the formation of localized energy states within the energy bandgap. These localized states act as recombination centers and increase the low energy electronic transitions. The dielectric constant was also found increased in the modified samples, exhibiting advantages for the formation of conducting thin films. A phase segregated morphology was obtained for the solvent treated PEDOT:PSS, and the MWCNTs were observed to be uniformly distributed throughout the polymer. Furthermore, the optical conductivity has been calculated to give comprehensive information about material properties and their systematic selection for desired applications. Keywords: PEDOT:PSS, Optical properties, Refractive index, Ethylene glycol, MWCNT, Optical conductivity

The perovskite solar cell structures: FTO/SnO2/(CH3NH3PbI3 or CH3NH3SnI3)/CuInSe2/Ag have been proposed and numerically analyzed using SCAPS-1D software. The performance of the designed cell structures are optimized by studying the effect of layers’ thickness, the electron affinity of transporting layers, and the bandgap of the hole transporting layer. The optimized power conversion efficiency of 20.36% and 18.89% are obtained for solar cells based on CH3NH3PbI3 and CH3NH3SnI3 absorbers, respectively. In addition, the effect of defect density in the perovskite layer and at the interfaces between different layers are investigated. The manuscript findings revealed that CuInSe2 nanocrystals act as an efficient inorganic HTL, and the defect density is a critical factor for affecting the performance of the cells.

In this paper, the degradation of fill factor with time of organic bulk heterojunction solar cells has been investigated up to 312 h. The experimental data of P3HT:PCBM solar cells has been analyzed theoretically to determine the parameters which affect the FF. The existing empirical formula has been applied to degradation data, and it was found to deviate drastically as the cell degrades, indicating that the correct behavior of solar cell is not imitated using the current FF formula. In view of the discrepancy, the expression for fill factor has been modified taking into account the material and device properties, which directly influence the working of a solar cell. All the values can be determined experimentally. The results of the modified expression gives better theoretical fit of FF with time. The results highlight the parameters which should be targeted in order to overcome the short lifetime of organic solar cells.

The perovskite materials based photovoltaic cells play a crucial role in the conversion of sunlight into electric energy. The commonly used perovskite materials are CH3NH3Pbl3 and CH3NH3Snl3. ln the present manuscript, a theoretical comparison is done by simulating the structures lTO/TiO2/CH3NH3Pbl3/p-Gr/Ag and lTO/TiO2/CH3NH3Snl3/p-Gr/Ag structures in AFORS-HET software under the illumination condition of AM 1.5G. Here, TiO2 and p-Graphene (p-Gr) play the role of electron transporting material and hole transporting material respectively with lTO and Ag as front and back contacts. The thickness of layers is directly related to the cost of the cells. Therefore, we optimized the CH3NH3Pbl3 and CH3NH3Snl3 layers thickness to observe the performance of the device. The power conversion efficiency of 10.62% is obtained for CH3NH3Snl3 based solar cell at optimized thickness of 800 nm as compared to 9.74% efficiency for CH3NH3Pbl3 based solar cell at an optimized thickness of 700 nm. The textured nature of front surface also enhances the efficiency 10.56% and 12.38% for CH3NH3Pbl3 and CH3NH3Snl3 respectively.

P3HT:PCBM is a popular material used for the fabrication of organic solar cells. However, the rapid degradation of these devices restricts their commercialization. It is, therefore, necessary to study the charge conduction mechanism in these materials with time. The Fowler-Nordheim (FN) plots of P3HT:PCBM based MIM devices show nonlinear behavior. As the device degrades, voltage at which substantial tunnelling is observed shifts to lower voltage, indicating the effect of diffused impurities. A clear transition from thermionic emission to field emission is observed. Interestingly, the degraded device shows multiple minima in the FN plots, indicating conversion of hole-only device into electron-only device at high voltages. The potential barrier at the interfaces has been estimated. Thus, by restricting the formation of interface states due to impurities, devices with higher lifetimes can be achieved.

The use of multilayer p-graphene as hole transporting layer has been successfully shown to improve the performance of perovskite solar cell. The structure of p-graphene/CH3NH3PbI3/n-cSi is designed and simulated in AFORS-HET software. We optimized the parameters of single layer p-graphene and obtained power conversion efficiency (PCE) of 12.21% under an illumination of AM 1.5G. With an increase in the number of p-graphene layers, the PCE falls down to 10.01%. The optimization of active layer parameters increases the PCE up to 12.27%. Further optimization of n-cSi parameters lead to the highest PCE of 16.75%. A significant effect of the operating temperature on the solar cell performance is observed. The effect of textured front surface on the solar cell performance is also studied and a PCE of 17.90% is obtained for textured surface as compared to 16.75% for planar surface. Our studies indicated that p-graphene may act as an efficient hole transporting layer in perovskite solar cell.

Bulk-heterojunction (BHJ) organic solar cells (OSCs) were fabricated with various active layer materials. Solar cells of configuration ITO/PEDOT:PSS/P3HT:PC61BM/Al, ITO/PEDOT:PSS/P3HT:PC71BM/Al and ITO/PEDOT:PSS/ PCDTBT:PC71BM/Al were fabricated. Current density-voltage (J-V) characteristics were measured in the dark and under illumination in ambient conditions. A single theoretical model was able to explain the J-V characteristics of all freshly prepared cells using realistic parameters. Copyright © 2015 VBRI Press.

This work presents a theoretical procedure to calculate various parameters needed for the installation of a photovoltaic water pump (PVWP) system. Specifically, the monthly optimum tilt angle of PV arrays is calculated, which will allow larger quantities of water to be pumped each month. For this, a simple performance optimization procedure is developed using solar radiation data. The investigations are based on the solar radiation data of New Delhi, India. The total amount of water pumped is compared with that by keeping the solar panels fixed throughout the year. The total amount of water that can be extracted by using manually adjustable arrays is found to be greater by 3–5%. This may be an alternative to an automatic sun tracker, which is not only expensive but also requires more space and maintenance. This method allows for analyzing the performance of low‐cost water pumping systems that may be used for both domestic and irrigation purposes.

Degradation and short shelf life have been observed experimentally in poly(3-hexylthiophene) (P3HT): 6,6-phenyl C61-butyric acid methyl ester (PCBM) based blend solar cells. Both dark and illuminated current–voltage characteristics could be explained quantitatively with a proposed single model for a typical degraded organic solar cell-glass/ITO/PEDOT:PSS/P3HT:PCBM/Al. It has been found that surface state density, interface thickness, tunneling coefficient and occupation probabilities of the interface states becomes important with the passage of time. To look into the problem the activity at ITO/PEDOT:PSS and P3HT:PCBM/Al interfaces are studied using realistic values of the interfaces. The experimental J–V characteristics is well explained with the inclusion of tunneling current through these surface states and becomes the dominant current component for the degraded cell. It is also found that surface state density increases to 1012–1013 cm−2 eV−1, which has been verified with C–V measurements and also is in agreement with our proposed model for BHJ solar cell after 150 h of fabrication.

Mobility and lifetime of the carriers are two very crucial parameters, which can account for the aging of a photovoltaic device, because changes in morphology, electrode/polymer interfaces, etc., will finally result in decrease of mobility and lifetime of carriers. In the present work, we have tried to explain our experimental data with the help of theoretical analysis based on our earlier model in which we have incorporated the activity at electrode interfaces in terms of density of surface states, thickness of interface layer, and tunneling probability. Calculations show that decrease in mobility for a cell under illumination is much faster than in a dark cell. Photoinduced oxidation plays a dominant role in fast degradation of the mobility. The lifetime is also seen to decrease because of modification of parameters such as interface thickness, density of interface states, and roughness.