Characteristics Of Heterojunctions Research Articles

Dark current in FTO/CZTS interface: a comprehensive comparison of practical Vs theoretical approach using SCAPS-1D

This study investigates the deposition of Cu2ZnSnS4 (CZTS) thin films on fluorine-doped tin oxide (FTO) and soda-lime glass (SLG) substrates using radio frequency (RF) sputtering at varying temperatures. A comprehensive characterization employing multiple analytical techniques was conducted. X-ray diffraction (XRD) analyses confirmed the amorphous nature of CZTS films being deposited up to 200 °C, while higher temperatures promoted increased crystallinity, with the presence of (112) and (220) planes observed at 300 °C and 400 °C. Rietveld refinement using Profex software revealed an increase in crystallite size with deposition temperature for films grown at 300 °C and 400 °C. Optical characterization through UV–vis spectroscopy unveiled a decrease in band gap energy with increasing deposition temperature, while the Urbach energy, associated with defects and imperfections, exhibited an inverse relationship with band gap and temperature. Experimental current–voltage (I-V) measurements using a Keithley source meter showed variations in the ideality factor with deposition temperature. SCAPS-1D simulations were performed to model the FTO/CZTS interface, incorporating experimental parameters. The simulated I-V behavior demonstrated a transition from recombination to diffusion-dominated current above 1.3 V forward bias. Simulations yielded higher ideality factors due to increased contributions from recombination and diffusion currents. Overall, this study provides insights into the growth, structural, optical, and electrical properties of CZTS thin films deposited by RF sputtering, enabling a comprehensive understanding of the FTO/CZTS heterojunction characteristics and their dependence on deposition temperature.

Influence of crystallinity and copper dopant concentration in Cu:NiO on their heterojunction characteristics with Al:ZnO

Influence of crystallinity and copper dopant concentration in Cu:NiO on their heterojunction characteristics with Al:ZnO

Assembly of WO3-Nb2O5-ZnIn2S4 with embedded quasi-planar heterojunction characteristics and its efficient and stable dark-state photoelectrochemical cathodic protection performance

Constructing a photoanode with both high dark-state protection performance and high stability remains a top priority for photoelectrochemical cathodic protection technology, especially in a marine environment (dark-state or rainy conditions) without hole scavenging agents. In this work, we developed a class of energy-storage quasi-planar heterojunctions (WO3-Nb2O5-ZnIn2S4) with directional paths (low onset potential and well-matched energy band) and embedded morphology. The co-design of embedded and directional paths reduces the carrier transport energy barrier at the composite interface, and increases the interface contact area, thereby achieving highly stable and sensitive dark-state energy storage and photoelectrochemical cathodic protection performance in 3.5 wt.% NaCl solution without hole scavenging agent (Dark-state energy storage efficiency increased by 43%. For carbon steel, the performance retention rate is 99.6% after 500 cycles, the performance retention rate is 89% after 5000 s).

Deciphering heterojunction layered double hydroxide-polyaniline-carbon nanotubes for phosphorus capture in capacitive deionization

The capacitive deionization (CDI) has emerged as a robust technology due to its effective performance in removing and recovering phosphate in wastewater. However, there are still challenges in achieving fast charge transfer and high capacity phosphorus storage simultaneously. In this study, a layered double hydroxide-polyaniline-carbon nanotubes composite material (ZnFe-PANI/CNT) with heterojunction and pseudocapacitive characteristics was fabricated via a simple and effective precipitation strategy. The existence of heterojunction and pseudocapacitance of ZnFe-PANI/CNT was confirmed through material performance testing Moreover, with its fast charge transfer and high ion storage performance, it was achieved high phosphate adsorption efficiency (94 %) and sustainable electrode regeneration in low concentration phosphate wastewater. Ultraviolet photoelectron spectroscopy (UPS) and density functional theory revealed the ability to accelerate charge transfer, which was contributed by the heterojunction ZnFe-PANI/CNT. In addition, it was found that the synergies of electrostatic attraction, ligand exchange and surface complexation contributed to the high phosphate capture ability in the acidic environments. The binuclear bidentate or mononuclear bidentate structures dominated the surface configuration of phosphate adsorption at pH 4–9.

Influence of copper on zinc oxide films and solar cell performance

Copper doped Zinc oxide and (n-ZnO / p-Si and n-ZnO: Cu / p-Si) thin films thru thickness (400±20) nm were deposited by thermal evaporation technique onto two substrates. The influence of different Cu percentages (1%,3% and 5%) on ZnO thin film besides hetero junction (ZnO / Si) characteristics were investigated, with X-ray diffractions examination supports ZnO films were poly crystal then hexagonal structural per crystallite size increase from (22.34 to 28.09) nm with increasing Cu ratio. The optical properties display exceptional optically absorptive for 5% Cu dopant with reduced for optically gaps since 3.1 toward 2.7 eV. Hall Effect measurements presented with all films prepared pure and doped have n-types conductive, with a maximum carriers concentrate of 3.9×1016 (cm-3 ) besides lower resistivity of 59.6 (Ω.cm) for films doped with 5% (Cu). The current- voltage (I-V) characteristics of heterojunction below illumination by incident power density (100 mW/cm2 ) showed that heterojunction (n-ZnO: 5%Cu / p-Si) has maximum efficiency (η =3.074 %).

Heterojunction characteristics and photoelectrochemical performance of TiO2 nanorods sensitized by zeolitic imidazolate framework

Traditional photocatalysts suffer from inferior utilization of solar light. Therefore, developing novel photocatalyst for better solar light harvesting is much required in the wake of current environmental problems arising from conventional energy technologies. Here we report synthesis and characterization of photocatalysts based on TiO2 nanorods (TNR) and Zeolitic Imidazolate Framework-9 (ZIF-9) and their photoelectrochemical properties. The TNRs were sensitized by ZIF-9 through solvothermal method. The presence of ZIF-9 on TNR formed a p-n heterojunction which assisted in initiating efficient charge separation and promoting injection of these carriers into the electrolyte. The heterojunction catalysts also exhibited enhanced optical properties in terms of extended absorption with reduced bandgap in comparison to the TNR film. The aforementioned properties manifested in improved photoelectrochemical performance with a current density of 0.94 mA/cm2, which is four times better than TNR and an applied bias photon to current efficiency (ABPE) of 0.27 %, which is five times better than TNR film alone. These superior properties of the processed ZIF-TNR demonstrate their potential for photoelectrochemical catalysis, thus paving the way for green hydrogen generation.

Density Functional Theory Calculations of Optoelectronic Properties of Individual and Encapsulated Magnesium Porphyrin in Carbon Nanotubes for Organic Nanohybrid Solar Cells

This research discusses incorporating a single magnesium porphyrin molecule into a semiconducting single‐walled carbon nanotube (SWCNT) for solar cell applications. Using density functional theory (DFT), the study examines the optical and electronic properties of the isolated magnesium porphyrin molecule and two configurations of the hybrid system. Results show structural stability due to charge transfer between the molecule and the nanotube. Different exchange‐correlation functionals (GGA and HSE06) yield varied bandgap results, affecting light absorption. Integration of the molecule into the SWCNT reduces the bandgap. Encapsulation of the molecule influences absorption and stability under irradiation. These encapsulated systems exhibit type II heterojunction characteristics, making them promising for organic solar cells based on SWCNTs, offering potential for highly efficient solar cells.

Modeling the electrical properties of heterojunctions using ANFIS, ANFIS-GA and ANFIS-PSO Models

The present research introduces a theoretical study that aims to utilize ANFIS in estimating and predicting the electrical behavior of heterojunctions. For this purpose, five different heterojunctions were chosen. The experimental datasets that represent the electrical behavior of the chosen heterojunctions were extracted and employed in ANFIS as targets. To enhance the ANFIS performance two hybrid heuristic algorithms, genetic algorithm (GAs) and particle swarm optimization (PSO) were combined with ANFIS. The major contribution of the current research is to predict the electric characteristics of heterojunctions using ANFIS and increase the modeling accuracy of ANFIS by optimizing the premise and consequent parameters using (GAs) and (PSO). Also, compare the proportion of enhancement produced by using ANFIS-GA and ANFIS-PSO to decide which of them is more powerful under the study conditions. However, to the author’s knowledge, the presented goals have not been investigated before for heterojunctions. The mean squared error (MSE), the correlation coefficient (R2), and the standard deviation error (Std. error) were calculated for all trained models. The modeling errors of ANFIS-GA and ANFIS-PSO were compared to the error values produced by ANFIS. According to modeling results, simulation ANFIS outputs follow the experimental data patterns in excellent response. Predictions of electrical characteristics for heterojunctions using the trained models provide acceptable results where the MSE values obtained by training ANFIS-PSO are lower than their values obtained by ANFIS and ANFIS-GA models. The improvements in average percentages in ANFIS performance when combined with GA and PSO are equal to 2.2% and 3%, respectively. Consequently, the proposed ANFIS-PSO model is more accurate in predicting the electrical behavior of heterojunctions under the study conditions.

A new semiconductor heterojunction SERS substrate for ultra-sensitive detection of antibiotic residues in egg

Antibiotic residues in animal-derived food (egg) are threatening human health. Semiconductor heterojunction surface-enhanced Raman scattering (SERS) substrates can be used for ultra-sensitive detection of antibiotic residues in egg. Here, a TiO2/ZnO heterojunction was developed as a new SERS substrate based on an interface engineering strategy. Due to strong interfacial coupling and efficient carrier separating in heterostructure, utilization rate of photo-induced electrons in substrate was improved greatly, which realized the efficient charge transfer in substrate-molecule system, resulting in a prominent SERS enhancement. Taking the detection of enrofloxacin residue in egg as an example, the limit of detection (LOD) is only 13.1 μg/kg, which is far below the European Union standard, and lower than LODs of other conventional analytical methods and existing noble metal-based SERS methods. More importantly, benefiting from high sensitivity and selectivity of heterojunction and fingerprint characteristics of SERS, multiple antibiotic residues in egg can be identified simultaneously.

A novel selenization-free chalcopyrite CIGSSe formation in a heat-treated Cu2Se/S/Ga3Se2/S/In3Se2 multilayer thin film (ML) and ML/n-Si heterojunction characteristics

Selenization or sulphurization is a standard method for developing copper-selenium-based ternary to quinary compounds. The route proved effective, but there are concerns about the high-risk management and potential explosion if mishandled. This article discusses a selenization/sulphurization-free fabrication of a CIGSSe thin film structure. Instead of selenization, a Cu2Se/S/Ga3Se2/S/In3Se2 multilayer thin film structure is chosen, and a simple post-annealing in high vacuum is used. The x-ray diffraction analysis hinted at a composite structure in as-deposited and a phase pure dominant chalcopyrite structure in the annealed film. The bandgap of 1.71 eV with a high absorption coefficient of 104/cm with smaller Urbach energy of 59 meV supports the dominant microstructure of the annealed thin film. Room temperature hall measurements also ensured the charge carrier transformation of n-type to p-type during annealing with the carrier concentration of 1016/cm3. The Au/p-CIGS/n-Si/Au heterojunction is developed, and current-voltage measurements are investigated.

Effects of Heat Treatment in Air Atmosphere on Dip Coating Deposited CdS Thin Films for Photo Sensor Applications

Objective: In this report, photo sensitive materials with enhanced charge carriers have been prepared using dip coating technique. Methods: Cadmium sulphide (CdS) is N-type semiconductor compound belonging to II-VI group. CdS nanoparticles were synthesized using non-aqueous chemical method and characterized by ultraviolet-visible (UV-Vis) absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy. CdS films were deposited on fluorine doped tin oxide (FTO) glass slides using dip coating method at different dip times and heat treated in air and analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis by X-rays (EDAX), mapping and atomic force microscopy (AFM). Results: Quantum confinement effect was observed in UV-Vis absorption spectra of CdS nanoparticles. Quenching of luminescence intensity and blue shift at smaller wavelengths were observed in PL spectra. Presence of highly dense rectangular shaped grains in CdS films and increment in particle sizes with increase in dip time were shown by AFM images. Selected area electron diffraction images showed ring patterns indicating polycrystalline nature of CdS nanoparticles. Increase in crystallite size and decrease in crystal defects by heat treatment in air and increment in grain size with increase in dip time were shown by SEM images. XRD analysis of CdS films showed polycrystalline nature. Conclusion: In previous work, preparation of dip coating deposited CdS films on FTO glass substrates for optoelectronic device applications such as photo sensors has not been reported. In this study, I-V characteristics of heterojunctions under dark and illumination conditions were discussed. Experimental results obtained in our study and their comparison with previous reports were also discussed.

P-n Homojunction perovskite solar cells: effects of ionic density and thickness of the doped layers

The p-n homojunction perovskite solar cells are promising in comparison to planar heterojunction perovskite solar cells. It is observed that the p-n homojunction provides an efficient built-in electric field for the photo-generated electron-hole pairs to dissociate into free charge-carriers and orient them to transport to the respective electrodes, thereby reducing the overall losses due to recombination processes. However, the existence of p-n homojunction, while in operation, is currently undergoing experimental tests. In this study, we simulated the current-voltage characteristics of both planar heterojunction and p-n homojunction perovskite solar cells. For simulation, we utilised a one-dimensional drift-diffusion equation. The current-voltage characteristics show a high fill factor for the p-n homojunction devices indicating better power conversion efficiency as compared to that of planar heterojunction devices. In addition, we report the spatial distribution of electron- and hole-density with variations in (i) the mobile ionic density, inherently present in the perovskite material and (ii) the thickness of p- and n-type perovskite layers. It is observed that the role of p-n homojunction ceases when the ionic density is higher than 1017 cm−3 or when one of the doped layers is substantially thicker as compared to the other. We correlate the cease of p-n homojunction to (i) the ionic effect which screens the built-in field, and (ii) the predominance of the effect of one doped layer over the other. The study provides impetus to the development of the p-n homojunction perovskite solar cells.

2D NiCo2S4 decorated on ZnIn2S4 formed S-scheme heterojunction for photocatalytic hydrogen production

The hydrothermal preparation of NiCo2S4/ZnIn2S4 photocatalysts with different mass ratios is studied. Ni-cobalt bimetallic sulfide nanosheets are grown on zinc-indium bimetallic sulfide to form a compact heterojunction. First, both NiCo2S4 and ZnIn2S4 exhibit N-type semiconductor characteristics, a heterojunction formed by both can reduce the surface reaction energy barrier and use its synergy, strengthening the charge self-diffusion between the two semiconductors, it means the formation of a strong electric field. From the electron transfer path and band structure, NiCo2S4/ZnIn2S4 has S-scheme heterojunction characteristics. NiCo2S4 is a reducing photocatalyst (RP), and ZnIn2S4 is an oxidative photocatalyst (OP). Under the action of built-in electric field (BIEF), strong photogenic electrons and holes exist in CB of RP (NiCo2S4) and VB of OP (ZnIn2S4). Thus, the overall redox capacity of the NiCo2S4/ZnIn2S4 heterojunction is enhanced. Using visible light, the composite material can be used for photocatalytic hydrogen production. It is further shown that the composite material has a good effect in photocatalytic hydrogen production under the sensitizer eosin Y (EY) system. The optimal hydrogen production is about 221.75 μmol when the mass ratios of NiCo2S4/ZnIn2S4 is 20%, and the photocatalytic activity of the composite is about 47 times that of ZnIn2S4. Notably, the stability of the composites is the better. A reasonable photo-catalytic mechanism is proposed based on the band gap and photoelectrochemical properties of heterojunction.

Optimized photoelectric characteristics of MAPbCl3 and MAPbBr3 composite perovskite single crystal heterojunction photodetector

MAPbBr3 single crystal (SC) thin layer was successfully grown on MAPbCl3 SC substrate to form perovskite SC heterojunction. Planar structure electrodes are deposited by thermal evaporation on the surfaces of MAPbCl3, MAPbBr3, and SCs heterojunction, respectively to evaluate their photoelectric performance. The SC heterojunction device exhibits excellent unidirectional conductivity in the voltage-current curves. Meanwhile, the current–time curves prove that SC heterojunction devices can effectively utilize the advantages of MAPbCl3 and MAPbBr3, possessing relatively low dark current (∼300 nA), which is comparable to the dark current of MAPbCl3, but very high photocurrent (∼3500 nA), which is equivalent to the photocurrent of MAPbBr3. Rather than the photocurrent overshot and decay occurring at the exposure of light illumination in the MAPbBr3 device, the photocurrent is extremely stable without overshot and decay in the SC heterojunction device. The light-to-dark ratio of the SC heterojunction device is twice that of MAPbCl3 device and three times that of MAPbBr3 device. Furthermore, the detectivity of the heterojunction device reaches as high as , an order of magnitude higher than MAPbCl3 and MAPbBr3. The excellent characteristics of SC heterojunction further expand the practical application prospect of perovskite materials.

Effect of copper on physical properties of CdO thin films and n-CdO: Cu / p-Si heterojunction

Transition metal Copper doped Cadmium oxide and (Cu: CdO and n-CdO: Cu / p-Si) thin films were prepared onto glass and p-type single crystal (111) Si substrates at temperature 300 K by thermal evaporation technique with thickness (400±30) nm. The effects of different Cu ratios on the CdO thin films and heterojunction of n-CdO / p-Si.. The X-ray diffraction analysis approves the CdO films are polycrystalline and cubic structure with lattice parameter of 0.4689 nm. The optical transmittance exhibits excellent optical absorption for 6% Cu doping. Decreased of optical band gap from 2.1 to 1.8 eV. Hall measurement approves that CdO material n type with a maximum carrier mobility of 144.6 (cm2 /Vs) with resistivity of 0.107991 (Ω.cm) were achieved for 6% Copper (Cu) doping. The I-V characteristics of heterojunction prepared under illumination was carried out by(100 mW/cm2) incident power density at different Cu doping.

Synthesis of ZnO@In2O3 heterojunction with unique hexagonal three-dimensional structure for ultra sensitive ethanol detection

The unique interface barrier characteristics of heterojunction have a significant impact on the gas sensing properties of composites. In this work, we report the successful synthesis of ZnO@In2O3 heterojunction nanocomposites with ultra sensitive response to ethanol by simple hydrothermal method and subsequent annealing treatment. SEM, TEM, XRD and other morphological characterization methods were used to detect the composites. Through the analysis of the characterization results, it can be found that the special structure of heterojunction is a three-dimensional structure which composed of ZnO hexagonal nanosheets and surface attached In2O3 nanoparticles, with a specific surface area of 63.27 m2/g. Measurements show that diameter of the nanosheets is 200–300 nm, the thickness is 40–60 nm, and the particle size of In2O3 nanoparticle is 30–60 nm. Due to the unique hexagonal three-dimensional structure, large specific surface area and rich mesoporous structure, gas sensing test results of the sensor prepared through ZnO@In2O3 heterojunction present that response value to 100 ppm ethanol at 160 °C is 28.6, which is much higher than pure ZnO and In2O3; It also presents the ability of rapid ethanol detection (response and recovery time are 8 s and 17 s); The synthesis of unique heterojunction structure greatly improves the sensitivity to ethanol, lower operating temperature significantly reduces energy consumption, and the repeatability and stability of sensors also perform excellent. Above advantages confirm that ZnO@In2O3 heterojunction nanocomposite is one of the ideal materials for rapid ethanol detection.

Electrical and Photoelectric Properties of Organic-Inorganic Heterojunctions PEDOT:PSS/n-CdTe

PEDOT: PSS thin films are widely used as transparent coatings in flexible semiconductor devices including solar cells. However, they are not widely used as transparent coatings in combination with crystal substrates. This work shows the possibility of using PEDOT:PSS thin films as a frontal transparent conducting layer in hybrid organic-inorganic Schottky type heterojunctions of the PEDOT:PSS/n‑CdTe, which were prepared by deposition of PEDOT:PSS thin films (using the spin-coating method) on crystalline cadmium telluride substrates. The current-voltage (in a wide temperature range) and capacitance-voltage (at room temperature) characteristics of heterojunctions were measurement and analyzed. It has been established that PEDOT:PSS/n-CdTe heterojunctions have good diode properties with a high rectification ratio RR≈105, a potential barrier height φ0 = 0.95 eV, and series Rs = 91 Ohm and shunt Rsh = 5.7 × 107 Ohm resistances. Analysis of the forward branches of the I–V characteristics of heterojunctions showed that the dominant charge transfer mechanisms are determined by the processes of radiative recombination at low biases (3kT/e <V <0.3 V) and tunneling through a thin depleted layer at high biases (0.3 V <V <0.6 V). Capacity-voltage characteristics are plotted in the Mott-Schottky coordinate, taking into account the influence of series resistance, measured at a frequency of 1 MHz. Used the C-V characteristic was determined the value of the built-in potential Vc = 1.32 V (it correlates well with the cutoff voltage determined from the current-voltage characteristics) and the concentration of uncompensated donors in the n-CdTe substrate ND-NA = 8.79 × 1014 cm-3. Although the photoelectric parameters of unoptimized PEDOT:PSS/n-CdTe heterojunctions are low, their photodiode characteristics (Detectivity D*> 1013 Jones) are very promising for further detailed analysis and improvement. The proposed concept of a hybrid organic-inorganic heterojunction also has potential for use in inexpensive γ- and X-ray detectors.

Determination of photovoltaic parameters of CIGS hetero junction solar cells produced by PLD technique, using SCAPS simulation program

In this study, CIGS ultrathin films of 52 nm, 89 nm, 183 nm and 244 nm thicknesses were grown on a n-Si substrate using PLD technique, then Ag/CIGS/Si/Al hetero-junction solar cells were formed by producing front finger and back contact. While the thickness of CIGS ultrathin film is increased, their grain sizes are also increased, crystal structures are developed and more light is absorbed within the thin film. The straight characteristics of hetero-junctions have been improved while the thicknesses of CIGS ultrathin film is decreased according to J-V characteristics of the hetero-junctions in the darkness. In addition, depending on CIGS ultrathin film thickness, the photovoltaic behavior of CIGS/Si hetero junction solar cells has been studied and interpreted in detail in this article. It can be concluded that CIGS/Si hetero-junction solar cell device produced based on CIGS ultrathin film of 183 nm thickness shows the highest short circuit current density and power conversion efficiency values among other thicknesses, with respect to J-V curve under the illumination (AM 1.5 solar radiation in 80 mW/cm2). Using SCAPS 1-D program, we have been able to successfully simulate CIGS/Si hetero-junction of 183 nm thickness.

Ni-Co-LDH and Zn-Co Prussian blue analogue derived hierarchical NiCo2O4@ZnO/ZnCo2O4 microspheres with enhanced electrochemical sensing performance towards pentachloronitrobenzene

In this work, we developed a hierarchical structure and multi-component synergistic metal oxide hybrid material, and explored its practical application in monitoring pentachloronitrobenzene (PCNB). We used the ZnO/ZnCo2O4, obtained by calcining Zn-Co Prussian blue analogue (PBA), as the substrate and integrated Ni-Co layered double hydroxide (LDH) on its surface and calcined to obtain hierarchical NiCo2O4@ZnO/ZnCo2O4 microspheres (MSs). Due to the p-n heterojunction characteristics of p-type semiconductor NiCo2O4 and ZnCo2O4 and n-type semiconductor ZnO and the high specific surface area of the microspheres supported by the hierarchical structure conductive network, when this material was used to modify the glassy carbon electrode (GCE), it significantly enhanced the electrochemical sensing performance towards PCNB. Therefore, a new type of electrochemical sensor was constructed based on NiCo2O4@ZnO/ZnCo2O4 MSs and molecularly imprinted polymer (MIP) for the sensitive and highly selective detection of PCNB. Among them, the MIP membrane was fabricated by cyclic voltammetry (CV), and differential pulse voltammetry (DPV) was used to detect PCNB. Under the optimum conditions, the reduction peak current density of PCNB was linearly related to the concentration from 0.05 to 5.5 μM with a detection limit of 8.33 nM and a good sensitivity of 6.118 μA⋅μM−¹⋅cm−². Furthermore, the proposed MIP sensor exhibited high selectivity, reproducibility, repeatability, and stability, and had been used for the detection of PCNB residues in licorice, river water, and soil samples with satisfactory results.

Determination of defect states and surface photovoltage in PTB7:PC71BM based bulk heterojunction solar cells

Defects formed during the device processing acts as recombination centers and shows adverse effects on the photovoltaic performance of the organic solar cells (OSCs). In this manuscript, a study on the effect of defect states on the characteristics of bulk heterojunction (BHJ) solar cells, consisted of unannealed or thermally annealed active layer (ActL) of PTB7:PC71BM blend, have been performed by using the illumination intensity-dependent current-voltage and frequency dependent impedance spectroscopy measurements. Our results indicate that the photovoltaic performance of devices based on annealed ActL is superior than the bench dried ActL due to thermal annealing induced improvement in the thin film morphology. The measured low-frequency capacitance-voltage (C–V) characteristics under varying illumination intensities show strong dependency on the photoexcitation however, the change in the C–V characteristics is found to be quite different for unannealed and annealed devices. The C–V characteristics are analyzed using the drift-diffusion model to extract the effective built-in voltage (Vbi) and the surface photovoltage as a function of illumination intensity. The capacitance-frequency characteristics under illumination reveal that the change in the capacitance is associated with the photo-induced carrier occupation in the intermixture donor-acceptor phases, which act as the defect states in such devices. Further, it is modeled to quantify the defect states and to demonstrate the importance of thermal annealing for improving the OSCs device performance.