The power conversion efficiency (PCE) of a ternary organic solar cell (TOSC) with an active layer consisting of PBDB‐T‐2F and two non‐fullerene materials Y6 and SF(BR)4 is simulated. Tungsten ...disulphide (WS2) is used as the hole transport layer (HTL) to reduce the contact resistance between the active layer and anode which enhances the internal quantum efficiency to 91.7%. It is found that the use of a highly absorbing non‐fullerene small molecule acceptor, SF(BR)4, enhances the absorption as well as improves the stability. Finally, the incorporation of the graded refractive index coating, in the form of moth‐eye shaped nanostructures, on the top of glass reduces the reflection losses and enhances the transmission coefficient from 0.88 to 0.94. Thus, the TOSC simulated here, of the structure moth‐eye‐AR/glass/ITO/WS2/PBDB‐T‐2F:Y6:SF(BR)4/PFN‐Br/Al, produces a PCE of 20.87%. The results presented in this paper are expected to provide useful guidance for fabricating highly efficient and stable hybrid bulk‐heterojunction solar cells.
Introduction of the non‐fullerene acceptor SF(BR)4 enhances the photon absorption in the region from 450 to 550 nm, and incorporation of the antireflection coating of graded refractive index of moth‐eye nanostructures reduces the reflection losses. Thus, a modified ternary organic solar cell (TOSC) with the structure moth‐eye‐AR/Glass/ITO/WS2/PBDB‐T‐2F:Y6:SF(BR)4/PFN‐Br/Al produces a simulated power conversion efficiency of 20.87%.
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-cyclopentacthiophen-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 BHJ OSCs with the blend of both donor and acceptor based on the same core structure.
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 and the results obtained from the conventional simulation, which are found to be in good agreement. It is found that the highest power loss occurs due to PThermal$P_{\text{Thermal}}$ in both OSC and PSC. Compared to conventional models, this model establishes a direct relationship between PCE and individual power losses that may occur in both OSCs and PSCs.
A novel mathematical model has been developed to simulate the power conversion efficiency (PCE) of organic solar cells (OSCs) and perovskite solar cells (PSCs). Unlike conventional models, it directly links PCE to specific power losses in both OSCs and PSCs, with PThermal$P_{\text{Thermal}}$ identified as the primary loss due to charge carrier thermalization.
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.
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 and applied to calculate ηPCE in three different BHJ OSC structures, one with a fullerene acceptor and two with different nonfullerene acceptors.
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.
Using the first-order perturbation theory and exciton-spin–orbit-photon-molecular-vibration-interaction (ESOPMVI) operator, the rates of reverse intersystem crossing (RISC) and thermally activated ...delayed fluorescence (TADF) are derived. It is shown that the pre-exponential factor of the rate of TADF is not an absolute constant as is commonly assumed. Instead, it depends on the square of the atomic number and the exchange energy, but it also depends on the triplet excitonic Bohr radius as a t –6, which enhances the rate of RISC by 4–6 orders of magnitude higher than the rate of the intersystem crossing, which undermines the dependence of the rate on the atomic number, and hence TADF can occur efficiently in metal-free organic solids. This provides a clearer understanding of the mechanism of TADF in metal-free organic light-emitting diodes as has been found recently experimentally.
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.
The power conversion efficiency (PCE) of a hybrid bulk hetero‐junction organic solar cell with an active layer of a blend of PBDT TS1 (donor) and PCBM (acceptor) incorporated with copper zinc tin ...sulfide (CZTS) quantum dots (QDs) and zinc oxide (ZnO) nanowires is simulated. It is found that the incorporation of CZTS‐QDs of a single radius (1.5 nm) enhances the PCE from 9.1% to 12.34% and of 13 different radii CZTS‐QDs elevates PCE to 14.96%. This enhancement occurs mainly due to the enhancement in absorption that enhances short‐circuit current density (Jsc) and fill factor (FF). Finally, a layer of ZnO nanowires is added on top of the glass to reduce the reflection losses and absorption of ultraviolet light in the active layer that causes degradation and reduces the stability of organic solar cells (OSCs). The hybrid structure, thus simulated, has an enhanced PCE of 16.32% and is expected to be relatively more stable. It is expected that the results of this simulation may inspire all researchers interested in the fabrication of highly efficient hybrid OSCs.
The incorporation of CZTS‐QDs of 13 different sizes and ZnO‐NWs on top of glass layer enhances the absorption and stability of a hybrid bulk‐hetero junction organic solar cell with the structure ZnO‐NWS/Glass/ITO/PEDOT:PSS/CZTS‐QDs:PBDT‐TS1:PCBM/Al and results in a PCE of 16.32%.
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