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The results of electrical and photoelectrical characterization of the interface and bulk properties of n+-ZnO/n-Si and poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/n+-ZnO/n-Si heterostructures are presented. It was found that the PEDOT:PSS layer deposited on the surface of zinc oxide increases the potential barrier at the ZnO/Si interface, leading to higher band bending in the silicon, which is important for solar cell applications. The recombination rate at the interface decreases because of the creation of an inversion layer in the silicon under operational conditions. The increase of the potential barrier in PEDOT:PSS/n+-ZnO/n-Si heterostructures results in the increase of the open-circuit voltage by 54–180%. The external quantum efficiency in PEDOT:PSS/n+-ZnO/n-Si heterostructures increases by 100% at 450 nm. [ABSTRACT FROM AUTHOR]

An expression for finding the dependence of narrowing the bands in silicon Eg on the level of illumination from the intrinsic absorption band (or short-circuit current) has been proposed. This expression is used to find experimental values of Eg in high-efficient silicon solar cells. The dependence Eg (J) or dependence Eg (JI), where JI is the shortcircuit current density, has been rebuilt into the Eg (nOC) dependence, where nOC is the excitation level in open-circuit conditions. With this aim, the generation-recombination balance equation was solved taking into account six recombination mechanisms in silicon, including Shockley-Reed-Hall recombination, radiative recombination, interband Auger recombination, surface recombination, non-radiative exciton recombination, and recombination in the space charge region. The latter two recombination terms are not taken into account in studies of the key parameters of silicon solar cells and in programs for simulating the characteristics of these solar cells. Therefore, in this work their correct definition was performed, their contribution was compared with the contribution of other recombination mechanisms, and it has been shown that the description of the characteristics and key parameters of silicon SC without taking them into account is insufficiently correct. The experimental dependences Eg (nOC) obtained in the work were compared with Schenk's theory. It has been shown that there is a good agreement between them. [ABSTRACT FROM AUTHOR]

Theoretical modeling of the optical and photovoltaic characteristics of highly efficient textured silicon solar cells (SC), including short-circuit current, open-circuit voltage and photoconversion efficiency, has been performed in this work. In the modeling, such recombination mechanisms as non-radiative exciton recombination relative to the Auger mechanism with the participation of a deep recombination level and recombination in the space charge region (SCR) was additionally taken into account. In a simple approximation, the external quantum efficiency of the photocurrent for the indicated SC in the long-wavelength absorption region has been simulated. A theory has been proposed for calculating the thickness dependences of short-circuit current, open-circuit voltage and photoconversion efficiency in them. The calculated dependences are carefully compared with the experimental results obtained for SC with the p + -i-α-Si:H/n-c-Si/i-n + -α-Si:H architecture and the photoconversion efficiency of about 23%. As a result of this comparison, good agreement between the theoretical and calculated dependences has been obtained. It has been ascertained that without taking into account recombination in SCR, a quantitative agreement between the experimental and theoretical light I-V characteristics and the dependence of the output power in the SC load on the voltage on it cannot be obtained. The proposed approach and the obtained results can be used to optimize the characteristics of textured SC based on monocrystalline silicon. [ABSTRACT FROM AUTHOR]

Crystalline Silicon (c-Si) remains a dominant photovoltaic material in solar cell industry. Currently, scientific and technological advances enable producing the c-Si solar cells (SCs) efficiency close to the fundamental limit. Therefore, combining the experimental results and those of modeling becomes crucial to further progress in improving the efficiency and reducing the cost of photovoltaic systems. We carried out the experimental characterization of the highly-efficient c-Si SCs and compared with the results of modeling. For this purpose, we developed and applied to the samples under investigation the improved theoretical model to optimize characteristics of highly efficient textured solar cells. The model accounts for all recombination mechanisms, including nonradiative exciton recombination by the Auger mechanism via a deep recombination centers and recombination in the space-charge region. To compare the theoretical results with those of experiments, we proposed empirical formula for the external quantum efficiency (EQE), which describes its experimental spectral dependence near the long-wave absorption edge. The proposed approach allows modeling of the short-circuit current and photoconversion efficiency in the textured crystalline silicon solar cells. It has been ascertained that the dependences of the short-circuit current on the open-circuit voltage and the dark current on the applied voltage at V < 0.6 V coincide with each other. The theoretical results, as compared to the experimental ones, allowed us to validate the developed formalism, and were used to optimize the key parameters of SCs, such as the base thickness, doping level and others. In this work, we have further generalized and refined the analytical approach proposed and used by us earlier to analyze high-efficiency solar cells and model their characteristics. [ABSTRACT FROM AUTHOR]

Short-circuit current, open-circuit voltage, and photoconversion efficiency of silicon high-efficiency solar cells with all back contact (BCSC) with planar surfaces have been calculated theoretically. In addition to the recombination channels usually considered in this kind of modeling, namely, radiative, Auger, Shockley-Read-Hall, and surface recombination, the model also takes into account the nonradiative trap-assisted exciton Auger recombination and recombination in the space charge region. It is ascertained that these two recombination mechanisms are essential in BCSCs in the maximum power operation regime. The model results are in good agreement with the experimental results from the literature. [ABSTRACT FROM AUTHOR]

The properties of the synthesized films of organic-inorganic perovskites CH3NH3PbI3 obtained at various ratios of starting reagents (PbI2 and CH3NH3I) have been studied. As a solvent, we used chemically pure dried dimethylformamide (DMF). Organicinorganic perovskites are promising for photovoltaic applications. It has been shown that regardless of the ratio of the starting reagents, single-phase perovskites are formed, at the same time the microstructure of the films changes significantly. It has been reported photoelectric and optical properties of synthesized films, namely: experimental and theoretical spectral dependences of the low-signal surface photovoltage and transmission. The band gap and the Urbach parameter dependence on the ratio of precursors were determined. It has been found that the materials' band gap depends on the ratio of precursors and equals to 1.59, 1.62 and 1.57 eV, while the characteristic Urbach energy equals to 18, 19 and 22 meV for the PbI2:CH3NH3I films with PbI2 ratio of 1:1, 1:2 and 1:3, respectively. It has been ascertained that the spectral dependences of the low-signal surface photovoltage are much more sensitive to the material microstructure and its electronic structure close to the absorption edge, while the optical transmission spectra are not so sensitive. The limiting value of the short-circuit current density for the films with different PbI2 and CH3NH3I ratios has been determined. [ABSTRACT FROM AUTHOR]

The influence of non-radiative exciton recombination (NRER) on the photoconversion efficiency in silicon solar cells with short Shockley-Read-Hall lifetimes tSRH has been studied. It has been shown that the efficiency reduction due to this effect is the stronger the shorter tSRH. The influence of NRER is most evident when the NRER time becomes shorter than tSRH. At sufficiently short tSRH, NRER substantially limits the optimal base doping levels of silicon solar cells, at which the photoconversion efficiency is maximal. [ABSTRACT FROM AUTHOR]

By comparison of the experimental dependence of bulk lifetime in silicon on the doping and excitation levels with theoretical calculations, it has been shown that a new recombination channel becomes operative when Shockley-Read-Hall lifetime is below 20 ms and the density of doping impurities or the excess electron-hole pair density is of the order of 1016 cm-3. This recombination mechanism is related to the non-radiative exciton Auger recombination assisted by the deep impurities in the bulk. The influence of non-radiative exciton recombination on the photoconversion efficiency in solar cells has been analyzed. It has been shown that the shorter the Shockley-Read-Hall lifetime, tSHR, the stronger its effect. In particular, for tSHR = 100 µs, this recombination channel leads to the reduction of the photoconversion efficiency by 5.5%. [ABSTRACT FROM AUTHOR]

Characteristics of basic silicon solar cells are experimentally researched and theoretically modeled using photons of incandescent lamps as sunlight simulator. It was established that increasing temperature evokes significant acceleration of short-circuit current growth. The reason of it is the shift of simulator spectrum to the higher wavelengths region as compared to the Sun one. This effect leads to a reduction in efficiency decrease for simulated sunlight with the increase of temperature. It should be taken into account in efficiency loss calculation with increase in the operating temperature. It has been shown that the results of theoretical modeling the temperature dependences for the short-circuit current density, open-circuit voltage and photoconversion efficiency are in good agreement with the experimental data obtained using the sunlight simulator. These results could be used to develop methods for investigation of temperature dependences of solar cell characteristics by using various sunlight simulators. [ABSTRACT FROM AUTHOR]