Random terpolymerization is an effective approach to achieving highly efficient and outdoor-stable terpolymer photovoltaics. However, the working principle behind this remains unclear. Herein, we report spectroscopic, morphological, and computational results...
With the gradual reduction of fossil fuels, it is essential to find alternative renewable sources of energy. It is important to take advantage of substitutes that are less expensive and more efficient in energy production. Photovoltaic concentrators (CPVs) are effective methods through which solar energy can be maximized resulting in more conversion into electrical power. V-trough concentrators are the simplest types of low-CPV in terms of design as it is limited to the use of two plane mirrors with a flat photovoltaic (PV) plate. A consequence of concentrating more solar radiation on a PV panel is an increase in its temperature that may decrease its efficiency. In this work, the thermal profile of the PV plate in a V-trough system will be determined when this system is placed in different geographical locations in Saudi Arabia. The simulation is conducted using COMSOL Multiphysics software with a ray optics package integrated with a heat transfer routine. The 21st of June was chosen to conduct the simulation as it coincides with the summer solstice. The employment of wind as a cooling method for V-troughs was investigated in this work. It was found that with the increase in wind speed, the PV panel temperature dropped significantly below its optimum operating temperature. However, due to the mirrors’ attachment to the PV panel, the temperature distribution on the surface of the panel was nonuniform. The temperature gradient on the PV surface was reduced with the increase of wind speed but not significantly. Reducing the size of the mirrors resulted in a partial coverage of solar radiation on the PV surface which helped in reducing the temperature gradient but did not eliminate it. This work can assist in testing numerous cooling models to optimize the use of V-troughs and increase its efficiency especially in locations having high ambient temperatures.
more than 30 years of empirical optimization [1,2] from the first proof of concept by Tang delivering only 1% power conversion efficiency (PCE) in 1986, [3] to develop the latest Y-series of non-fullerene acceptor (NFA) molecules [4,5] that now yield efficiencies close to 20%. [6][7][8][9][10][11] The field of OPV has always been in need of design principles that could guide the synthesis of new molecules. In parallel to molecular engineering, our understanding of the photophysics governing the solar cell performances has considerably increased in the last 30 years, and such sets of meaningful design rules have started to solidify. [12][13][14][15] Furthermore, first principlebased computational materials chemistry has progressed to the point where energy levels can not only be computed in the gas phase, but also extrapolated to films, which allows for screening many potential structures of OPV materials and selecting the most promising for synthesis. [14] For low-bandgap NFA-based solar cells, we previously showed that the acceptor's ionization energy has to be ≈0.45 eV higher (more negative with respect to vacuum) than that of the donor, to maximize exciton quenching by hole transfer from the acceptor to the donor and in turn the solar cells' internal quantum efficiency (IQE). [12,14] We showed that this hole transfer efficiency sets a ceiling to the solar cells' IQE. The 0.45 eV ionization energy offset ΔIE was shown to be required to counterbalance energy level bending (measured as bias potential B) at the donor-acceptor (D/A) interface, which increases the energy of the interfacial charge transfer (CT) and thus impedes the exciton-to-CT-state transition if ΔIE is low. [12,14,16] The interfacial energy level bending is a consequence of the energetic landscape in NFA-based blends, more specifically the interaction of charges with the surrounding molecules' (NFA and donors) intrinsic quadrupole moments. [12,14,15,17,18] On the other hand, the bending facilitates charge separation (CT to free charge conversion) and diffusion from the interface, explaining the observation of barrier-less charge generation in the top-performing OPV systems. [19] Very recently, we reported that the same applies to ternary blends, composed of one donor and two acceptors. [20] Interestingly, the IQE follows the average IE of both acceptors weighted by their blending (weight) ratio. [20] While Molecular engineering of organic semiconductors provides a virtually unlimited number of possible structures, yet only a handful of combinations lead to state-of-the-art efficiencies in photovoltaic applications. Thus, design rules that guide material development are needed. One such design principle is that in a bulk heterojunction consisting of an electron donor and lower bandgap acceptor an offset (ΔIE) of at least 0.45 eV is required between both materials ionization energies to overcome energy level bending at the donor-acceptor interface, in turn maximizing the charge separation yield and the cell's internal quantum efficiency. The present...
The use of photovoltaic (PV) systems presents a great solution to high energy demand. Many factors limit the output of PV systems. One method of increasing the output of PV systems is to employ concentrators. The function of these concentrators is to increase the amount of solar radiation falling on a PV panel using optical devices. In this work, a simulation of a low concentrated photovoltaic system (LCPV) (V-trough model) will be conducted using COMSOL Multiphysics software package. The ray-tracing technique, based on the finite-element method, was used to study the performance of a V-trough without the incorporation of a tracking system. By investigating the effect of the mirrors’ inclination angles on the performance of the system, the optimum inclination angles were determined. The simulation was done for a non-tilted concentrator photovoltaic (CPV) system if placed in different geographical locations in Saudi Arabia with the inclination of the mirrors being changed every hour of the daylight. It was found that the concentration ratio of the suggested model increased for the city of Jeddah, for example, by 171% and 131% for double and partial coverage cases, respectively. In order to reduce the operation cost, the simulation was repeated with the restriction of the mirrors’ inclination to only three positions during the day. The concentration ratio decreased in this case by not more than 14%. When mirrors were fixed throughout the day, the concentration ratio dropped to about 50%. Such simulations will assist in investigating different designs of PV systems prior to their manufacturing. In addition, it could assist in determining the best geographic location for such CPV systems.
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