IHJPAS. 36 (4) 2023 147 This work is licensed under a Creative Commons Attribution 4.0 International License *Corresponding Author: Naeem.Nahi1104a@ihcoedu.uobaghdad.edu.iq Abstract In this paper, the fill factor of the N749/π“π’πŽπŸ solar cell is studied and calculated using the analysis method at standard conditions; i.e., at room temperature T=300k and 100 mW π‘π‘š2 irradiation. The current density was derived and calculated using the donor-acceptor model according to the quantum transfer theory in DSSC solar cells. We estimate the influence parameters in the dye-sensitized solar cells DSSC that's an equivalent circuit to the I-V curves for three solvents. The fill factor parameters of the N749/π“π’πŽπŸ device are found to be 0.137,0.146 and 0.127 with Butanol, Ethanol and Acetonitrile for carrier concentration 1.5 Γ— 1018 1 π‘π‘š3 respectively. The photovoltaic characteristics 𝐼𝑆𝑐 , π‘‰π‘œπ‘ , πΌπ‘šand π‘‰π‘š are calculated depending on the current-voltage (J-V) characteristics of the device at room temperature. As a result of the fill factor analysis, N749/π“π’πŽπŸ cells showed different fill factors dependent on solvents type for the 𝐼𝑆𝑐 and π‘‰π‘œπ‘ . Keywords: The Fill Factor , N749/TiO2 Solar Cells. 1. Introduction The increased energy crisis and environmental problems will be necessary for the substantial exploration of renewable and clean energy materials[1]. The technology of renewable energy is vital part to reduce green-house gases and reduce all risks posed by global warm. Transition to renewable energies sources of electric was a vital solution to risks problems posed by global warm[2]. The electric generates from solar cells is the best option for the sustainable energy doi.org/10.30526/36.4.3236 Article history: Received 23 January 2023, Accepted 21 February 2023, Published in October 2023. Ibn Al-Haitham Journal for Pure and Applied Sciences Journal homepage: jih.uobaghdad.edu.iq Theoretical Calculation of The Fill Factor of N749/π“π’πŽπŸ Solar Cells 𝐍𝐚𝐞𝐞𝐦 𝐍𝐚𝐑𝐒 𝐀𝐛𝐝 π€π‹πˆ * Department of Physics, Collage of Education for Pure Science Ibn Al-Haitham, University of Baghdad, Baghdad, Iraq. π‡πšππ’ 𝐉. 𝐌. 𝐀π₯ βˆ’ π€π πžπšπ₯𝐲 Department of Physics, Collage of Education for Pure Science Ibn Al-Haitham, University of Baghdad, Baghdad, Iraq. Hossain Milani Moghaddam Department of Solid-State Physics, Faculty of Basic Sciences, University of Mazandaran, Babolsar, Iran. https://creativecommons.org/licenses/by/4.0/ mailto:Naeem.Nahi1104a@ihcoedu.uobaghdad.edu.iq mailto:drNaeem.Nahi1104a@ihcoedu.uobaghdad.edu.iq mailto:hadi.j.m@ihcoedu.uobaghdad.edu.iq mailto:milani@umz.ac.ir IHJPAS. 36 (4) 2023 148 requirement of the world [3]. Solar cells are an essential diverse entirety to be solved the increasing energy crisis that will eventually replace energy sources like fossil fuels in increasing resources [4]. Now, the dye-sensitized solar cells DSSC become a more significant great interest in technological of solar energy conversion as a result of low costs, optical properties and ease of production [5] . However, the DSSCs are promised devices consisting of a light-sensitive and another electrode together with an electrolyte can convert the light energy into electrical[6]. As such, the electron transfer process occurs from the donor to the acceptor level states[7], it requires to the alignment of both energy levels states and it is close to each other donor and acceptor.In addition to fundamental and important reactions, Hadi et al indicate that reorganization energy is the main parameter to understanding of mechanism electron transfer processes in variety electronic devices [8]. In heterostructure interfaces, the theory for electron transfer with molecules essentially occurred between molecule donor energy levels and solid acceptor under concept of donor-acceptor model for electron transfer potential [9]. The fill factor (FF) is an important parameter because it determines the power that a solar cell can generate. It's well known that it is influenced by the recombination current[10].The calculation of the fill factor in the current generation of DSSCs is the main key for further enhancement efficiency improvement[11].The calculation of current density and the fill factor role are used to calculate the efficiency of the solar cell [12]. Fill factor analysis of solar cells is the best and most efficient method to diagnose the thermal stability problem accurately[10]. In this work ,we study and calculate the fill factor of N749 contacted with TiO2semiconductor depending on estimated the photovoltaic characteristics 𝐼𝑆𝑐 , π‘‰π‘œπ‘ , πΌπ‘šand π‘‰π‘š using the current-voltage (J-V) curves. 2.Theory The fill factor defines as the ratio of actual max power for the production of short-circuit current (Isc) and pen-circuit voltage (Voc) . It calculates by using [13]. 𝐹𝐹 = π‘‰π‘šπ‘πΌπ‘šπ‘ π‘‰π‘œπ‘πΌπ‘ π‘ (1) Where π‘‰π‘šπ‘ and πΌπ‘šπ‘ are the maximum power voltage and current, π‘‰π‘œπ‘ and 𝐼𝑠𝑐 denote the open circuit voltage and the short circuit current are evaluated from current 𝐼(𝐸) – voltage 𝑉(π‘£π‘œπ‘™π‘‘) curves . The electronic current 𝐼(𝐸) is given by [14]. 𝐼(𝐸) = 𝑒 βˆ‘ 𝑇(𝐸)𝐹(𝐸) (2) where 𝐹(𝐸) is the Fermi distribution of system , 𝑇(𝐸) is transmission coefficient and given by . 𝑇(𝐸) = 2πœ‹ Δ§ |〈𝐢𝐢βŒͺ|2πœŒπ‘’ (𝐸) (3) Where 𝐢𝐢 is strength of electronic coupling and πœŒπ‘’(𝐸) is effective density in system ,its written as [15]. πœŒπ‘’ (𝐸) = πœŒπ‘†π‘™π‘’/ ( 6 πœ‹ ) 1 3⁄ (4) where 𝑙𝑒 is effective length and πœŒπ‘† is electronic density in semiconductor is [16]. πœŒπ‘† = 𝜌𝐡(𝐸)𝑑𝑆 βˆ’2 3⁄ βŒ©οΏ½Μ‚οΏ½βŒͺ (5) IHJPAS. 36 (4) 2023 149 Where 𝜌𝐡(𝐸) is the density of state in dye system , 𝑑𝑠 is the atomic density of TiO2 and βŒ©οΏ½Μ‚οΏ½βŒͺ is the density of state in system and writes as . ( ℷ𝑆 𝐡+βˆ†π‘’0)2 4ℷ𝑆 𝐡𝑇 βŒ©οΏ½Μ‚οΏ½βŒͺ = 1 √4πœ‹β„·π‘† π΅π‘˜π΅π‘‡ 𝑒 βˆ’ ( ℷ𝑆 𝐡+βˆ†π‘’0)2 4ℷ𝑆 π΅π‘˜π΅π‘‡ (6) Where βˆ†π‘’0 is the driving energy , π‘˜π΅ is the Boltzmann constant and T is room temperature .The reorganization energy ℷ𝑆 𝐡 (eV) is [17]. ℷ𝑆 𝐡(𝑒𝑉) = 𝑒2 8πœ‹πœ€Β° [ 1 𝐷 [ 1 𝑛2 βˆ’ 1 πœ€ ] βˆ’ 1 2𝑅 [ π‘›π‘†π‘’π‘š 2 βˆ’π‘›2 π‘›π‘†π‘’π‘š 2 +𝑛2 1 𝑛2 βˆ’ πœ€π‘†π‘’π‘š 2 βˆ’πœ€2 πœ€π‘†π‘’π‘š 2 +πœ€2 1 πœ€2 ]] (7) where 𝑒 is electronic charge , πœ€Β° is permittivity. The D and R are the radius of the molecule and the distance between molecule and semiconductor, 𝑛 and πœ€ are refractive index and dielectric constant of solvent, nSe is the refractive index of semiconductor and Ξ΅Se is the dielectric constant of semiconductor. The radius is [18]. 𝐷 = ( 3 4πœ‹ 𝑀 π‘πœŒ ) 1 3 (8) where molecular weight M, Avogadro number N, and the density of the material is ρ. Furthermore, the fill factor is ratio relative to J-V curve's maximum power is unitless Inserting Eqs.(4) ,(5) and (6) in Eq.(3) to give 𝑇(𝐸) = 2πœ‹ Δ§ 𝜌𝐡(𝐸) √4πœ‹β„·π‘† π΅π‘˜π΅π‘‡ |〈𝐢𝐢βŒͺ|2𝑒 βˆ’ ( ℷ𝑆 𝐡+βˆ†π‘’0)2 4ℷ𝑆 π΅π‘˜π΅π‘‡ 𝑙𝑒 ( 6 πœ‹ ) 1 3⁄ 𝑑𝑆 βˆ’2 3⁄ (9) here ℷ𝑆 𝐡 is the useful transition energy, βˆ†π‘’0 is the driving free energy and T is the temperature, inserting the Eq. (9) in Eq. (2) an assume continuum media for donor and acceptor and integrated to results . 𝐼(𝐸) = 2πœ‹π‘’ Δ§ |〈𝐢𝐢βŒͺ|2 √4πœ‹β„·π‘† π΅π‘˜π΅π‘‡ 𝑒 βˆ’ ( ℷ𝑆 𝐡+βˆ†π‘’0)2 4ℷ𝑆 π΅π‘˜π΅π‘‡ 𝑙𝑒 ( 6 πœ‹ ) 1 3⁄ 𝑑𝑆 βˆ’2 3⁄ ∫ 𝜌𝐡(𝐸)𝐹(𝐸) 𝐸 0 𝑑𝐸 (10) The solution integral in Eq.(10) is given [19]. ∫ 𝜌𝐡(𝐸)𝐹(𝐸) 𝐸 0 𝑑𝐸 = 𝑛𝑠……(11) Where 𝑛𝑠 is electronic concentration at the semiconductor’s ,the Eq. (10) becomes . 𝐼(𝐸) = 2πœ‹π‘’ Δ§ |〈𝐢𝐢 βŒͺ|2 √4πœ‹β„·π‘† π΅π‘˜π΅π‘‡ 𝑒 βˆ’ ( ℷ𝑆 𝐡+βˆ†π‘’0)2 4ℷ𝑆 π΅π‘˜π΅π‘‡ 𝑙𝑒 ( 6 πœ‹ ) 1 3⁄ 𝑑𝑆 βˆ’2 3⁄ 𝑛𝑠 (12) The atomic density 𝑑𝑆 is [19]. 𝑑𝑆 = 3 2𝐷𝑛 ( 𝑁𝑒 𝐸𝐹 ) (13) IHJPAS. 36 (4) 2023 150 Where 𝐷𝑛 is the number of states per atom per eV in the semiconductor , 𝑁𝑒 is carrier concentration and 𝐸𝐹 is the Fermi energy. 2. Results The generic of N749/TiO2 the solar cells may be described by a fill factor parameter according to the current density model consisting of a donor-acceptor ideal junction. The scenario calculates the current density parameters, which can fit the calculate and plot I-V curve and is estimated from the I-V curves all parameters to calculate the fill factor. The reorganization energy ℷ𝑆 𝐡(𝑒𝑉) can be calculated according to Eq. (7) and (8). The radii of N749 and TiO2 are calculated due to Eq.(8) with inserting molecular weight and mass density M= 1364.98 g/mol and 𝜌 = 1.28 g cm3 [20]) for N749 dye [20] and M=79.866g/mol and 𝜌 = 4.23 g cm3 [21] for TiO2 to results radii are 7.47 𝐴0 and 1.96 𝐴0for both N749 and TiO2 respectively . The reorganization energy is deduced using Eq.(7) as follows ;we insert both dielectric constant 55 and refractive index 2.609 of TiO2 semiconductor [21] and refractive index 1.3993, 1.359 22 and 1.3441with dielectric constant 17.51 , 24.55 and 37.5 of 1-Butanol , Ethanol(EtOH) and Acetonitrile(MeCN) solvents [22] the results are tabulated in Table(1). Table 1.Results of calculated the reorganization energy ℷ𝑆 𝐡(𝑒𝑉) of N749 /𝑇𝑖𝑂2 devices. Type of solvents Refractive index(n)[22] Dielectric constant(πœ€)[22] ℷ𝑆 𝐡(𝑒𝑉) 1-Butanol 1.399 17.51 0.329 Ethanol(EtOH) 1.359 24.55 0.363 Acetonitrile(MeCN) 1.344 37.5 0.383 Atomic constant 𝑑𝑆 calculates via Eq.(13) with taking concentration of carrier 𝑁𝑒 = 1.4 Γ— 1014π‘π‘šβˆ’3[23] and Fermi energy 𝐸𝐹 = 4.52𝑒𝑉 [24] and density of states 𝐷𝑛 = 8 (state /eV) of TiO2 [25] ,result is 5.80 Γ— 1018 1 π‘š3 .Taking into account the electronic concentration 𝑛𝑠 = 1.5 Γ— 1024 1 π‘š3 [26], we determined the electronic current using Eq.(12) with appropriate electronic strength coupling |〈CCETβŒͺ|2=0.1, 0.2,0.3,0.4,0.5, 0.6,0.7, 0.8, 0.9 ,1,1.1and 1.2Γ— 10βˆ’2 |eV|2 , effective length 𝑙𝑒𝑓𝑓 = 3𝐴0[27] and ℷ𝑆 𝐡 (𝑒𝑉) from Table(1) in accordance with the improved MATLAB program method, the results are list in Table (2) for N749/TiO2 devices . Table (2). The electronic current of N749 /TiO2 devices with three solvents at carrier concentration 1.5 Γ— 1018 1/π‘π‘š3. Strength coupling |βŒ©πΆπΆπΈπ‘‡βŒͺ|2x10βˆ’2 |eV|2 The electronic current 𝐼(Amper) 1-Butanol Ethanol Acetonitrile 0.1 1.4166E-04 1.0010E-04 8.0888E-05 0.2 2.8331E-04 2.0019E-04 1.6178E-04 0.3 4.2497E-04 3.0029E-04 2.4266E-04 0.4 5.6663E-04 4.0038E-04 3.2355E-04 IHJPAS. 36 (4) 2023 151 The current density of three sample devices would be obtained by dividing the results of the current on the area of the solar cell 0.158 cm2 [28] results of current density for N749/TiO2 with 1-Butanol , EtOH and MeCN solvents are shown in Table (3). Table 3.Results of current density of N749 / TiO2devices with three solvents at carrier concentration 1.5 Γ— 1018 1/π‘π‘š3. 0.5 7.0828E-04 5.0048E-04 4.0444E-04 0.6 8.4994E-04 6.0057E-04 4.8533E-04 0.7 9.9160E-04 7.0067E-04 5.6622E-04 0.8 1.1333E-03 8.0076E-04 6.4710E-04 0.9 1.2749E-03 9.0086E-04 7.2799E-04 1 1.4166E-03 1.0010E-03 8.0888E-04 1.1 1.5582E-03 1.1010E-03 8.8977E-04 1.2 1.6999E-03 1.2011E-03 9.7066E-04 1.3 1.8415E-03 1.3012E-03 1.0515E-03 1.4 1.9832E-03 1.4013E-03 1.1324E-03 1.5 2.1249E-03 1.5014E-03 1.2133E-03 Strength coupling |βŒ©πΆπΆπΈπ‘‡βŒͺ|2x10βˆ’2 |eV|2 The current density A/π‘π‘š2 1-Butanol Ethanol Acetonitrile 0.1 8.9656E-04 6.3351E-04 5.1195E-04 0.2 1.7931E-03 1.2670E-03 1.0239E-03 0.3 2.6897E-03 1.9005E-03 1.5359E-03 0.4 3.5862E-03 2.5341E-03 2.0478E-03 0.5 4.4828E-03 3.1676E-03 2.5598E-03 0.6 5.3794E-03 3.8011E-03 3.0717E-03 0.7 6.2759E-03 4.4346E-03 3.5837E-03 0.8 7.1725E-03 5.0681E-03 4.0956E-03 0.9 8.0691E-03 5.7016E-03 4.6076E-03 1 8.9656E-03 6.3351E-03 5.1195E-03 IHJPAS. 36 (4) 2023 152 However, the I -V characteristic of current density I(mAcm2) and voltage in Volt at carrier concentration 1.5 Γ— 1018 1 π‘π‘š3is shown in table (4) for 1-Butanol , Ethanol (EtOH) and Acetonitrile (MeCN) solvents devices . Table 4.Results of I-V characteristic of N749 TiO2devices with three solvents at carrier concentration 1.5 Γ— 1018 1/π‘π‘š3. Butanol Ethanol Acetonitrile V(Volt) 𝐼(𝐴) V(Volt) 𝐼(𝐴) V(Volt) 𝐼(𝐴) 0.829 0 0.8423 0 0.8423 0 0.8 8.9656E-04 0.8 6.3351E-04 0.8 5.1195E-04 0.75 1.7931E-03 0.75 1.2670E-03 0.75 1.0239E-03 0.7 2.6897E-03 0.7 1.9005E-03 0.7 1.5359E-03 0.65 3.5862E-03 0.65 2.5341E-03 0.65 2.0478E-03 0.6 4.4828E-03 0.6 3.1676E-03 0.6 2.5598E-03 0.55 5.3794E-03 0.55 3.8011E-03 0.55 3.0717E-03 0.5 6.2759E-03 0.5 4.4346E-03 0.5 3.5837E-03 0.45 7.1725E-03 0.45 5.0681E-03 0.45 4.0956E-03 0.4 8.0691E-03 0.4 5.7016E-03 0.4 4.6076E-03 0.35 8.9656E-03 0.35 6.3351E-03 0.35 5.1195E-03 0.3 9.8622E-03 0.3 6.9687E-03 0.3 5.6315E-03 0.25 1.0759E-02 0.25 7.6022E-03 0.25 6.1434E-03 0.2 1.1655E-02 0.2 8.2357E-03 0.2 6.6554E-03 0.15 1.2552E-02 0.15 8.8692E-03 0.15 7.1673E-03 0.1 1.3448E-02 0.1 9.5027E-03 0.1 7.6793E-03 1.1 9.8622E-03 6.9687E-03 5.6315E-03 1.2 1.0759E-02 7.6022E-03 6.1434E-03 1.3 1.1655E-02 8.2357E-03 6.6554E-03 1.4 1.2552E-02 8.8692E-03 7.1673E-03 1.5 1.3448E-02 9.5027E-03 7.6793E-03 IHJPAS. 36 (4) 2023 153 0 1.4278E-02 0 10.0507E-3 0 10.0507E-3 The values of I-V parameters are obtained according to the plot of the calculated I-V data, as shown in Figure 1. A B IHJPAS. 36 (4) 2023 154 C Figure 1. Shows the I-V graph of N749/TiO2 device with A-1-Butanol , B-Ethanol(EtOH) and C- Acetonitrile(MeCN) solvents. The 𝐼𝑆𝑐(π‘šπ΄/π‘π‘š2, π‘‰π‘œπ‘ Volt , πΌπ‘š(π‘šπ΄/π‘π‘š2) and π‘‰π‘š Volt can be obtained from the I-V curve in figure(1) ,the values of these parameters with three solvents at carrier concentration 1.5 Γ— 1018 1/π‘π‘š3are listed in table (5) below. Table 5. Results of illuminated I-V calculated and fill factor of N749 /TiO2 devices with three solvents at carrier concentration 1.5 Γ— 1018 1/π‘π‘š3. The fill factor is calculated for three sample devices using Eq.(1) by inserting the values of current and voltage from the Table(5) to results0.137 , 0.146 and 0.127 for N749 /TiO2 devices with 1- Butanol , Ethanol(EtOH) and Acetonitrile(MeCN) solvents 4. Discussion For the heterojunction N749/TiO2 photovoltaic, the current density (I) is calculates as a function of reorganization energy and strength coupling with same values of concentration and atomic mass results of the reorganization energy of the N749/TiO2are shown in Table(1),these results reveal slightly increasing with increasing the dielectric constant and with decreasing the refractive index of solvents. The results of reorganization energy indicated the ability of system with solvents to start electron transfer process more efficiently .The results of reorganization energy is more effect on the quantity of current and current density and finally effected the characteristic of solar cell through effecting the fill factor and efficiency of cells. The results in Table(1) are obtained by stepwise changing the value of polarity parameter of solvents in reorganization energy expression .The N749/TiO2 photovoltaic has low reorganization energy 0.329 eV with 1-Butanol solvent comparing with large reorganization energy 0.383 eV with Acetonitrile solvents . Variables The electronic concentration 1/π‘π‘š3 Butanol Ethanol Acetonitrile 𝐼𝑆𝑐(π‘šπ΄/π‘π‘š2) 1.428 E-02 1.0057E-2 1.005E-02 π‘‰π‘œπ‘ Volt 0.829 0.8301 0.842 πΌπ‘š(π‘šπ΄/π‘π‘š2) 2.193E-03 1.676E-03 1.479E-03 π‘‰π‘š Volt 0.738 0.728 0.728 F.F 0.137 0.146 0.127 IHJPAS. 36 (4) 2023 155 To investigate the photovoltaic performance of N749/TiO2 device, we must estimate the quantitative values of fill factor (FF) according to calculate current density and graph I-V in Figure (1).Table (2) shows the currents are different with varied reorganization energy and the strong coupling values of the N749/TiO2 solar cell. The current decreases upon increasing the reorganization energy but current increases with increasing the strength coupling , as seen in the current increased alternatively with increasing strength coupling from 0.1 Γ— 10βˆ’2|eV|2 to reach maximum current at 1.5 Γ— 10βˆ’2|eV|2 . The increased value of current and current density is ascribed to the transfer of more electron-hole pairs in the absorber N749/TiO2 system which separates into electrons and holes at the interface of N749/TiO2 heterojunction, it leads to an excess of photocurrent. In fact, the current and current density in Tables (2) and (3) decrease with increasing the reorganization energy and reach to higher current density with 1-Butanol solvent comparing with lower current density with Acetonitrile solvents . Furthermore, the maximum current density was 1.3448E-02 with 1-Butanol comparing with minimum current density was 7.6793E-03 with Acetonitrile and it increased with increasing strength coupling . Three curves of current density I(mA/Cm2) vs. Voltage (volt) of heterojunction N749 black dye- TiO2 in solar cell devices at concentrations 1.5 Γ— 1018 1/πΆπ‘š3 plotted and instead as shown in Figure 1 which are calculated at STC, i.e. 100 mW/ Cm2 and 25 0C. The curves are the calculated I-V curves, which are obtained by theoretical donor-acceptor model for electron transfer. Depending on the I-V curves, the values of parameters 𝐼𝑆𝑐 , π‘‰π‘œπ‘ , πΌπ‘šand π‘‰π‘š can be fixed and gained respectively ,there are limited in Table(5). The electron transfer significantly influences the 𝐼𝑆𝑐 of the I-V curve, which is moved through interface from donor to acceptor in variety devices of solar cells. That Isc could be improved slightly by increasing the electron transfer from donor to acceptor .Also ,the π‘‰π‘œπ‘ increases slightly when 𝐼𝑆𝑐 increased, while obvious change in both πΌπ‘š and π‘‰π‘š are observed .The influence of the πΌπ‘š and π‘‰π‘š parameters on the estimation of fill factor from the I-V curve, therefore ,it is quantificational revealed as seen in Table(5). In turn and based on the parameters that's gotten above, the values of the fill factor of each curve is obtained .The difference in fill factor was obvious, this difference indicated the difference in efficiency of solar cell.The fill factor of system devices is higher with Ethanol and reach to 0.146 ,while the fill factor was minimum and determined to equal 0.127 with Acetonitrile solvent for N749/TiO2 devices .The fill factor was not uniform with reorganization energy and I-V characteristic .However, the non-uniformity indicated to the different solvents type that used in N749/TiO2solar cells devices, which might be due to the uneven and effect of electron transfer rate of N749/TiO2 during the charge transfer process. The 𝐼𝑆𝑐significantly effected the π‘‰π‘œπ‘ of the I-V curve, which is co-directionally moved following the variety of 𝐼𝑆𝑐. When πΌπ‘š increases, no obvious change was observed Fill Factor and the shape of I-V curve in Figure (1). Figure (1) shows three I-V curves and become more declining between the maximum 𝐼𝑆𝑐 point and the maximum point voltage .No obvious change was observed in π‘‰π‘œπ‘ and 𝐼𝑆𝑐 and the shape of I-V curve when fill factor varies, so that FF is varied when πΌπ‘š decreases .In fact , the fill factor was influenced by πΌπ‘š and π‘‰π‘š . 5. Conclusions In conclusion, the fill factor increases with increasing both πΌπ‘š and π‘‰π‘š and dependence of the 𝐼𝑆𝑐 and Voc of N749/TiO2 cells based on the donor-acceptor model. It was confirmed that reorganization energy effected the current density . However, the πΌπ‘š and π‘‰π‘š are the main parameters that dominantly contribute to fill factor ,the fill factor different depending on the Im IHJPAS. 36 (4) 2023 156 of the devices .For N749/TiO2 devices , the 𝐼𝑆𝑐 and π‘‰π‘œπ‘ were the main parameters of fill factor decreases . However, the contribution of the fill factor decreased as the 𝐼𝑆𝑐to rose with increasing πΌπ‘š .It can be estimated that the N749/TiO2 cell has potential improved fill factor by optimizing πΌπ‘š and π‘‰π‘š or decreasing 𝐼𝑆𝑐 and π‘‰π‘œπ‘On the other hand N749/TiO2with Ethanol has a higher fill factor ratio 0.146 than other solvents, but the ratio of fill factor reduced to 0.127 with Acetonitrile due to the rapid decrease in the πΌπ‘š and π‘‰π‘š. Therefore, we suggest that optimize the fill factor led to reduce the 𝐼𝑆𝑐 for the N749/TiO2cell by optimizing the N749/TiO2 contacts and electron transfer . References 1. Tajamul, H. S.; Wei, W.; Technoeconomic Analysis of Dye Sensitized Solar Cells (DSSCs) with WS2/Carbon Composite as Counter Electrode Material, Inorganics magazine, 2022, 10, 191-201. https://doi.org/10.3390/ inorganics10110191. 2. Timothy, W.; Kenneth, P. 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