daniel dodzi yao setsoafia

This article presents a new mathematical model for simulating the power conversion efficiency (PCE) of organic solar cells (OSCs) and perovskite solar cells (PSCs). This model incorporates all power losses that can occur before the charge carriers are collected by their respective electrodes. This includes power loss due to thermalization of the charge carriers above the bandgap (PThermal$P_{\text{Thermal}}$), charge carrier recombination (Prec)$P_{\text{rec}} \left.\right)$, dissociation of excitons (PBI)$P_{\text{BI}} \left.\right)$, and the transport of free charge carriers to their respective electrodes through the energy off‐sets (PB)$P_{\text{B}} \left.\right)$. By quantifying each power loss, the model can simulate the net electrical power generated by a solar cell and estimate its PCE. The validity of the mathematical model is tested by comparing the calculated PCE of an OSC and a PSC with their experimental results …

Perovskite solar cells, a third‐generation photovoltaic technology, have recently emerged as a game‐changing innovation. However, lead (Pb) is a toxic heavy metal, and it is crucial to explore lead‐free perovskite solar cells with continuously improving efficiency for long‐term development. Recently, materials researchers have discovered a lead‐free double perovskite solar cell material, Cs2InBiBr6 with a small direct bandgap of 1.27 eV and strong thermodynamic and mechanical structural stability. The power conversion efficiency of Cs2InBiBr6‐based perovskite solar cells is not reported yet. To investigate its potential, a solar cell capacitance simulator to analyze the solar cell structure of FTO (Fluorine Doped Tin Oxide)/ETL (Electron Transport Layer)/Cs2InBiBr6/HTL (Hole Transport Layer)/Au, selecting appropriate hole transport materials and electron transmission materials to achieve high efficiency is used …

We have simulated the effect of changing the end groups in BTP core with five organic units of 1,3-Indandione (IN), 2-thioxothiazolidin-4-one (Rhodanine), propanedinitrile (Malononitrile), (2-(6-oxo-5,6-dihydro-4H-cyclopenta[c]thiophen-4-ylidene)malononitrile) (CPTCN) and 2-(3-oxo-2,3-dihydroinden-1-ylidene (IC), and two halogenated units of (4F) IC and (4Cl) IC on the optical and photovoltaic properties of the BTP DA’D core molecular unit. Thus modified, seven molecular structures are considered and their optical properties, including HOMO and LUMO energies and absorption spectra are simulated in this paper. On the basis of HOMO and LUMO energies, it is found that two of the seven molecules, BTP-IN and BTP-Rhodanine, can act as donors and the other four, BTP-(4F) IC, BTP-(4Cl) IC, BTP-CPTCN and BTP-IC, as acceptors in designing bulk heterojunction (BHJ) organic solar cells (OSCs). Using these combinations of donors and acceptors in the active layer, eight BHJ OSCs, such as BTP-IN: BTP-(4F) IC, BTP-IN: BTP-(4Cl) IC, BTP-IN: BTP-CPTCN, BTP-IN: BTP-IC, BTP-Rhodanine: BTP-(4F) IC, BTP-Rhodanine: BTP-(4Cl) IC, BTP-Rhodanine: BTP-CPTCN and BTP-Rhodanine: BTP-IC, are designed, and their photovoltaic performance is simulated. The photovoltaic parameters Jsc, Voc and FF for all eight BHJ OSCs and their power conversion efficiency (PCE) are simulated. It is found that the BHJ OSC of the BTP-IN: BTP-CPTCN donor–acceptor blend gives the highest PCE (14.73%) and that of BTP-Rhodanine: BTP-(4F) IC gives the lowest PCE (12.07%). These results offer promising prospects for the fabrication of high-efficiency …

Using the density functional theory (DFT), the influence of substitution of electron-donating (OCH3 and OH) and electron-accepting (F and Cl) groups on the peripheral thiophene units of DRTB-T donor molecule is studied. By optimizing the geometric structure, HOMO and LUMO energies, reorganization energies, optical properties, and photovoltaic properties are simulated. It is found that the ionization potential of the electron-donating derivatives (DRTB-4OCH3 and DRTB-4OH) reduces, but it increases for the electron-accepting derivatives (DRTB-4F and DRTB-4Cl) in comparison with that of DRTB-T. It is also found that the absorption spectra of the electron-donating derivatives (DRTB-4OCH3 and DRTB-4OH) get redshifted, but these get blue shifted for the electron-accepting derivatives (DRTB-4F and DRTB-4Cl) in comparison with those of DRTB-T. These changes in the electronic and optical properties of the modified structures result in higher PCE in BHJ OSCs with the blended active layer of DRTB-4F: NITI, DRTB-4Cl: NITI, in comparison with that of OSC with the active layer of DRTB-T: NITI and the highest being 15.0% in DRTB-4Cl: NITI. Our results may be expected to provide valuable insights into design optimization, leading to the fabrication of more efficient OSCs.

In this paper, a mathematical model and the relevant computer code are developed to quantify the extraction probability rate of charge carriers (EPRCC) in a perovskite solar cell of the structure: Glass/ITO/PEDOT: PSS/CH3NH3PbI3/PC60BM/Al to investigate the influence of interfaces and grain boundaries. It is found that, without passivation, the probability of an electron generated near the anode reaches to the cathode is only 35%, while by passivating the interfaces and grain boundaries, this probability increases to about 60% at maximum power point condition. Likewise, without passivation, the probability of a hole generated near the electron transport layer‐active layer interface reaches to the hole transport layer is only 15%, while by passivating the interfaces and grain boundaries, this probability increases to about 45% at maximum power point condition. The same calculation has been done at the short …

A new analytical expression that directly relates the open‐circuit voltage (Voc) in perovskite solar cells (PSCs) to the quasi‐Fermi level splitting (QFLS), interface energy offsets, and nonradiative recombination losses has been derived. It is found that the QFLS of the active layer plays a dominant role in enhancing Voc of PSCs. The newly derived Voc is applied to two PSCs with the hole transport layer (HTL) of poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine], and poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) and found that the first PSC has a higher Voc, which agrees well with the experimental results. It is found that both PSCs exhibit saturation of Voc at the higher charge carrier generation rates and hence at higher light intensities. The lower Voc in PSC with P3HT as HTL is attributed to the stronger band bending and higher interfacial defects. In accordance with the results, a large quasi‐Fermi level splitting and a …

Thermal stability, closely associated with the operating temperature, is one of the desired properties for practical applications of organic solar cells (OSCs). In this paper, an OSC of the structure of ITO/PEDOT:PSS/P3HT:PCBM/ZnO/Ag was fabricated, and its current-voltage (J-V) characteristics and operating temperature were measured. The operating temperature of the same OSC was simulated using an analytical model, taking into consideration the heat transfer, charge carrier drift-diffusion and different thermal generation processes. The simulated results agreed well with the experimental ones. It was found that the thermalization of charge carriers above the band gap had the highest influence on the operating temperature of the OSCs. The energy off-set at the donor/acceptor interface in the bulk heterojunction (BHJ) was shown to have a negligible impact on the thermal stability of the OSCs. However, the energy off-sets at the electrode/charge-transporting layer and BHJ/charge-transporting layer interfaces had greater impacts on the operating temperature of OSCs at the short circuit current and maximum power point conditions. Our results revealed that a variation over the energy off-set range from 0.1 to 0.9 eV would induce an almost 10-time increase in the corresponding thermal power generation, e.g., from 0.001 to 0.01 W, in the cells operated at the short circuit current condition, contributing to about 16.7% of the total solar power absorbed in the OSC.

Using the optical transfer matrix method, we optimized the layered structure of a conventional and an inverted BHJ OSC with the active layer made of blended PTB7-Th:PNDI-T10 by maximizing the optical absorption and, hence, the JSC. The maximum JSC thus obtained from the optimised structure of the inverted OSC was 139 Am−2 and that of the conventional OSC was 135 Am−2. Simulation of the electric field distribution in both inverted and conventional OSCs showed that the formation of a single CIP was obtained in the active layer of thickness 105 nm in both OSCs. As the light incidents from the ITO side, it was found that excitons were generated more closely to ITO electrode, which favors the efficient charge transport and collection at the opposite electrodes in the inverted OSC, which produces higher JSC.

This is an introductory chapter to develop the concept of electrons, holes and charge carriers and the distinction between them. Several applications of charge carriers in semiconductor devices are briefly described and both inorganic and organic devices are covered. The involvement of charge carriers in the mechanisms of operation of organic solar cells (OSCs) and organic light emitting diodes (OLEDs), including the thermally activated delayed fluorescence (TADF) OLEDs is also described.

DFT and TD-DFT calculations of HOMO and LUMO energies and photovoltaic properties are carried out on four selected pentathiophene donor and one IDIC-4F acceptor molecules using B3LYP and PBE0 functionals for the ground state energy calculations and CAM-B3LYP functional for the excited state calculations. The discrepancy between the calculated and experimental energies is reduced by correlating them with a linear fit. The fitted energies of HOMO and LUMO are used to calculate the Voc of an OSC based on these donors and acceptor blend and compared with experimental values. Using the Scharber model the calculated PCE of the donor-acceptor molecules agree with the experiment. It has been found that fluorine substitution can be used to improve charge transport by reducing the electron and hole reorganization energies of the molecules. It is also found that the introduction of fluorine onto the donor pentathiophene unit of the donor molecule results in a change of polarity of the distributed charges in the molecule due to the high electronegativity of the fluorine atom. The quantum chemical potential (μ), chemical hardness (η) and electronegativity (χ), and electrostatic potential maps (EPMs) are also calculated to identify different charge distribution regions in all five molecules.

A comprehensive study of the operating temperature () of three nonfullerene (NF) acceptor‐based bulk heterojunction organic solar cells (BHJ OSCs), two conventional (OSC1 and OSC3) and one inverted (OSC2) structure, is presented. A quantitative analysis of the thermal power generated by photon absorption in transport layers and electrodes, thermalization of photoexcited charge carriers, tail‐state recombination, and resistive heating is conducted. For all three OSCs, the dependence of operating temperature on the voltage is simulated and it is found that OSC1 and OSC2 operate at about 320 K and OSC3 at 319 K. It is also found that the thermal power generated due to thermalization (PT) and absorption in other than the active layer () in OSC3 are smaller than those in both OSC1 and OSC2 but the thermal power generated due to the resistive heating (PR) is larger in OSC3 than in OSC1 and …

An alternative approach to simulate the power conversion efficiency (ηPCE) of bulk heterojunction organic solar cells (BHJ OSCs), as a product of efficiencies of absorption (ηabs), dissociation (ηdis), and extraction (ηext), is presented. Although ηabs and ηdis do not directly contribute to the simulation of ηPCE, the approach enables us in understanding their roles in optimizing the power conversion efficiency of BHJ OSCs. This method is applied to simulate ηPCE as a function of the thickness of active layer for three different BHJ OSC structures, one with a fullerene acceptor and two with two different nonfullerene acceptors. The results are found to be in good agreement with those from the previous simulation and experimental works and are expected to be useful in optimizing the thickness of the active layer.

In this paper, characterisation of exciton generation is carried out in three bulk-heterojunction organic solar cells (BHJ OSCs)—OSC1: an inverted non-fullerene (NF) BHJ OSC; OSC2: a conventional NF BHJ OSC; and OSC3: a conventional fullerene BHJ OSC. It is found that the overlap of the regions of strong constructive interference of incident and reflected electric fields of electromagnetic waves and those of high photon absorption within the active layer depends on the active layer thickness. An optimal thickness of the active layer can thus be obtained at which this overlap is maximum. We have simulated the rates of total exciton generation and position dependent exciton generation within the active layer as a function of the thicknesses of all the layers in all three OSCs and optimised their structures. Based on our simulated results, the inverted NF BHJ OSC1 is found to have better short circuit current density which may lead to better photovoltaic performance than the other two. It is expected that the results of this paper may provide guidance in fabricating highly efficient and cost effective BHJ OSCs.