Organic Thin-film Solar Cells Research Articles

Modeling of a hybrid thermal photovoltaic (PVT) collector based on thin film organic solar cells

The new trend is towards limiting the amount of silicon used in PVT collectors, by favoring new thin film technologies (other than that of Si). The most common technologies today are based on (CdTe), (CIS), (CIGS) and (CIGSS) which have high electrical efficiencies of around 20.5%. However, these technologies have certain drawbacks: less advanced industrialization, limited raw materials and in competition with other uses, toxicity of materials (in particular CdTe) which makes recycling more complex but at a high cost. New concepts of PVT collectors have therefore been explored for twenty years based on the use of organic materials such as the polymer (P3HT:PCBM). In this paper, we studied a three-dimensional modeling of a hybrid thermal photovoltaic (PVT) collector based on (P3HT:PCBM) by the Comsol 5.4 software and matlab. The results show that The temperature of the PVT collector reach a maximum value of the 110.09°C, the fluid flow velocity reach a value of 2.75*10−3 m/sec, higher thermal efficiency (85.77%) and lower electrical efficiency (6.57%) compared to the PVT collector based on monocrystalline silicon.

Probing Charge Generation Efficiency in Thin-Film Solar Cells by Integral-Mode Transient Charge Extraction.

The photogeneration of free charges in light-harvesting devices is a multistep process, which can be challenging to probe due to the complexity of contributing energetic states and the competitive character of different driving mechanisms. In this contribution, we advance a technique, integral-mode transient charge extraction (ITCE), to probe these processes in thin-film solar cells. ITCE combines capacitance measurements with the integral-mode time-of-flight method in the low intensity regime of sandwich-type thin-film devices and allows for the sensitive determination of photogenerated charge-carrier densities. We verify the theoretical framework of our method by drift-diffusion simulations and demonstrate the applicability of ITCE to organic and perovskite semiconductor-based thin-film solar cells. Furthermore, we examine the field dependence of charge generation efficiency and find our ITCE results to be in excellent agreement with those obtained via time-delayed collection field measurements conducted on the same devices.

Plasmon assisted optical absorption and reduced charge recombination for improved device performance in polymer solar cell

Silver and Calcium (Ag:Ca) bi-metallic nano-partices have been successfully synthesized using a chemical reduction processes. The nano-partices were intended to be used in the solar absorber layer of thin film organic solar cell (TFOSC) to assist in improving optical absorption and charge transport processes in polymers blend medium. The nanocomposite (Ag:Ca) is expected to exhibit local surface plasmon resonance (LSPR) and far-field scattering from the interaction with the incident photons. The absorber layer of TFOSC, in this investigation, is prepared from the mixture of poly-(3-hexylthiophene) (P3HT): [6,6]-phenyl C61 butyric acid methyl ester (PC61BM). Devices were fabricated at various concentration of metal nano-particles in the solar absorber layer, as 1%, 3%, and 5% by weight, to be able to determine the optimum concentration of the dopant. Hence, the experimental evidences clearly showed that performance of the solar cell is dependent on the concertation of the metal nano-particles. Consequently, the power conversion efficiency (PCE) value has increased by 75% with a remarkable improvement in device fill factor of 53.4% at an optimum doping level of 3%. The optical and morphological properties of the synthesized nano-particles are well presented and discussed in terms of the data collected using transmission and scanning electron microscopy (TEM & SEM) and other complimentary methods.

Emission Spectroscopy Investigation of the Enhancement of Carrier Collection Efficiency in AgBiS2-Nanocrystal/ZnO-Nanowire Heterojunction Solar Cells.

Eco-friendly solar cells were fabricated using interdigitated layers comprising ZnO nanowires (NWs) and infrared absorbing AgBiS2 nanocrystals (ITO/ZnO NWs/AgBiS2/P3HT/Au). The quality of ZnO NWs was studied using photoluminescence and Raman spectroscopy to identify the defects in ZnO NWs influencing solar cell performance. Oxygen vacancies and Zn interstitial sites, among various recombination sites, were observed to be the main sites for carrier recombination, which hinders the carrier collection in the solar cells. Accordingly, the power conversion efficiency of AgBiS2 solar cells exhibited a good correlation with the number of oxygen vacancies. The structural order and electron-phonon interaction in ZnO NWs were also investigated via Raman scattering spectroscopy. A lower concentration of oxygen vacancies and zinc interstitials (Zni) resulted in a higher structural order as well as a weaker electron-phonon interaction in ZnO NWs. When ZnO NWs were treated at 500 °C in oxygen with the lowest oxygen vacancy concentration, the solar cells (500-O2 solar cell (SC)) demonstrated an external quantum efficiency of approximately 70% in the visible region and a corresponding internal quantum efficiency of more than 80%. The 500-O2 SC exhibited a power conversion efficiency of 5.41% (JSC = 22.21 mA/cm2, VOC = 0.41 V, and FF = 60%) under quasi one-sun illumination. New methods that can efficiently reduce oxygen vacancies and Zni without affecting the structural order of ZnO NWs would further enhance the carrier collection efficiency. Moreover, since ZnO is a key electron transport material for constructing not only colloidal quantum dot solar cells but also other emerging solar cells, such as organic thin-film solar cells, the present findings provide significant information for improving their performance.

Numerical investigation of the effects of copper sulfide nanoparticles on hole transport layer of thin-film organic solar cells

Numerical investigation of the effects of copper sulfide nanoparticles on hole transport layer of thin-film organic solar cells

Laminated high-performance semi-transparent perovsktie solar cells: Enabled by sticky polyethyleminine as glue

Electric glue plays a key role in laminating top electrodes for organic and perovskite thin-film solar cells. However, there has been seldom reported for chemically reactive low–work function electrode yet. In this paper, polyethyleneimine (PEI) was developed as transparent top electrode adhesive, surface modifier for air-stable low–work function, and barrier to suppress the chemical corrosion of metal electrode in perovskite solar cells. The lamination was finished under room temperature with a pressure as low as 8 MPa, which is a very mild condition for device fabrication. The solar cells with transparent top electrode laminated for 10min had the best performances, in which the average value of PEI thickness between silver nanowires and the adjacent layer was found to play a key role in adjusting the performance of solar cells.

Determination of The Electronic Properties of Some Organic Electroluminescent 2-[3-(Methyl/Ethyl/p-Methylbenzyl)-5-oxo-1H-1,2,4-triazol-4(5H)-yl]-isoindoline-1,3-diones with Density Function Theory

The potential organic electroluminescent properties of 4,5-dihydro-1H-1,2,4-triazol-5-one derivatives that have recently attracted much of the scientists' interest is discussed. The electronic features of these heterocyclic organic compounds are examined with computational methods. The calculation operations were conducted with the high-performance server systems running on Windows operating systems. The geometries of the studied molecules were plotted using the GaussView 5.0 computer program. Theoretical calculations were conducted using the Gaussian09W program. Then, the HOMO-LUMO shapes of the molecules that were optimized with theoretical calculations were obtained. The HOMO-LUMO energy difference (ΔE) of each molecule was calculated in terms of eV. The results were compared with the values obtained from relevant literature. According to the theoretical and simulation results obtained from the B3LYP 6-311G++(d,p) and CAMB3LYP 6-311G++(d,p) basic set calculations of the DFT (Density Functional Theory) method used in this study; when the HOMO-LUMO energy differences were examined, it was determined that from among the studied candidate molecules, there were potential molecules that have/could have optoelectronic features. Therefore, it is expected that the study will shed light on synthetic organic chemistry procedures in terms obtaining optoelectronic materials. Organic electronic devices are quite remarkable due to their optoelectronic features. These devices can be examined under three main headings. These are organic light emitting diode (OLED), organic thin-film transistors (OTFT) and organic solar cells. These devices are usually structured in the form of anode-organic material-cathode layers placed on top of each other.

Two-Dimensional Nanomaterials for Boosting the Performance of Organic Solar Cells

The thin-film organic solar cells (OSCs) are currently one of the most promising photovoltaic technologies to effectively harvest the solar energy due to their attractive features of mechanical flexibility, light weight, low-cost manufacturing, and solution-processed large-scale fabrication, etc. However, the relative insufficient light absorption, short exciton diffusion distance, and low carrier mobility of the OSCs determine the power conversion efficiency (PCE) of the devices are relatively lower than their inorganic photovoltaic counterparts. To conquer the challenges, the two-dimensional (2D) nanomaterials, which have excellent photoelectric properties, tunable energy band structure, and solvent compatibility etc., exhibit the great potential to enhance the performance of the OSCs. In this review, we summarize the most recent successful applications of the 2D materials, including graphene, black phosphorus, transition metal dichalcogenides, and g-C3N4, etc., adapted in the charge transporting layer, the active layer, and the electrode of the OSCs, respectively, for boosting the PCE and stability of the devices. The strengths and weaknesses of the 2D materials in the application of OSCs are also reviewed in details. Additionally, the challenges, commercialization potentials, and prospects for the further development of 2D materials-based OSCs are outlined in the end.

Optimized Thin-Film Organic Solar Cell with Enhanced Efficiency

Modification of a cell’s architecture can enhance the performance parameters. This paper reports on the numerical modeling of a thin-film organic solar cell (OSC) featuring distributed Bragg reflector (DBR) pairs. The utilization of DBR pairs via the proposed method was found to be beneficial in terms of increasing the performance parameters. The extracted results showed that using DBR pairs helps capture the reflected light back into the active region by improving the photovoltaic parameters as compared to the structure without DBR pairs. Moreover, implementing three DBR pairs resulted in the best enhancement gain of 1.076% in power conversion efficiency. The measured results under a global AM of 1.5G were as follows: open circuit voltage (Voc) = 0.839 V; short circuit current density (Jsc) = 10.98 mA/cm2; fill factor (FF) = 78.39%; efficiency (η) = 11.02%. In addition, a thermal stability analysis of the proposed design was performed and we observed that high temperature resulted in a decrease in η from 11.02 to 10.70%. Our demonstrated design may provide a pathway for the practical application of OSCs.

Plasmonic nano-particles mediated energy harvesting in thin-film organic solar cells

A Cd-doped ZnO nano-composite (Cd:ZnO) was synthesized using wet chemistry, and then incorporated into the photo-active layer of a thin film organic solar cell (TFOSC) to assist photon harvesting. The nano-composite (NC) formed different sized nano-structures that are beneficial to optical absorption and charge transport processes in the TFOSC. The effects on the NC were studied using a solar absorber medium composed of a poly(3-hexylthiophene) (P3HT) and 6-6-phenyl-C61-butyric acid methyl ester (PCBM) blend with standard device architecture: ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al. The electrical and optical properties of the photoactive films were investigated at various doping levels of Cd:ZnO NC in the medium. The composite showed interesting local surface plasmon resonance, which significantly impacted on the performance of the cells. Consequently, the power conversion efficiency of the TFOSC grew by 84% compared to the reference cell. It is also noted that Cd:ZnO is environmentally stable and compatible for solution device processing.

Effective energy harvesting in thin film organic solar cells using Ni:Zn as bimetallic nanoparticles

This article explores the effect of bimetallic plasmonic nanocomposites in the solar absorber layers of thin-film organic solar cells (TFOSCs) for possible improvement in harvesting solar energy. To achieve this goal, a new nanocomposite composed of Nickel and Zinc (Ni: Zn) was successfully synthesized by the use of a chemical reduction processes. The effect of bimetallic nanocomposites was studied using a photoactive medium, which comprises of poly-(3-hexylthiophene) (P3HT) [6,6]-phenyl C61 butyric acid methyl ester (PC61BM) blend and doped with Ni:Zn at different concentrations. Consequently, an improved power conversion efficiency value up to 4.78% was found at 1% Ni:Zn bimetallic concentration by weight compared to reference solar cell. This is a clear indication of the influence of Ni:Zn bimetallic nanoparticles on the performance of TFOSC. These effects have been realized by the occurrence of local surface plasmon resonance (LSPR) phenomenon caused by Ni: Zn nanoparticles in polymer medium.

Metal nano-composite induced light trapping and enhanced solar cell performances

A tri-metallic nano-particles (NPs) involving Silver, Iron and Nickel (Ag:Fe:Ni) was successfully synthesized using a wet chemical reduction method. The synthesized nano-composite (Ag:Fe:Ni) has exhibited polycrystalline morphology in powder form, which was used as nano-composite in a P3HT:PCBM blend solar absorber layer of the thin film organic solar cell (TFOSC) to enhance the collection of photons. Consequently, the power conversion efficiency (PCE) of the thin film organic solar cells grew by 42% due to the incorporation of NPs in the devices structure. However, the concentration of metal nano-particles was varied from 0% to 3% by weight to determine the optimum doping level of the NPs for maximum effect in the solar absorbers. The effect of the metal nano-particles is clearly evident by high short circuit current (Jsc) of TFOSC which is attributed to improve the dissociation of exciton and charge transport processes in the medium. The optical and morphological characteristics of the nanoparticles were discussed in terms of the measured parameters.

Evaluation of hole mobility in non-peripherally alkyl-substituted tetrabenzotriazaporphyrin thin films by MIS-CELIV method

Charge carrier mobility measurement of donor materials for organic thin-film solar cells, 1,4,8,11,15,18,22,25-octaalkyltetrabenzotriazaporphyrin (CnTBTAPH2), was carried out by using metal-insulator-semiconductor charge carrier extraction by linearly increasing voltage (MIS-CELIV) method. The estimated carrier mobility, which is based on the hopping conduction process between the molecular columns composed with CnTBTAPH2, sequentially decreased depending on the alkyl-chain length. The alkyl-chain length dependence of the mobility was discussed by taking the evaluated activation energy and the inter-column spacing into consideration.

Electronic excitation spectra of organic semiconductor/ionic liquid interface by electrochemical attenuated total reflectance spectroscopy

The interface of organic semiconductor films is of particular importance with respect to various electrochemical devices such as transistors and solar cells. In this study, we developed a new spectroscopic system, namely electrochemical attenuated total reflectance ultraviolet (EC-ATR-UV) spectroscopy, which can access the interfacial area. Ionic liquid-gated organic field-effect transistors (IL-gated OFETs) were successfully fabricated on the ATR prism. Spectral changes of the organic semiconductor were then investigated in relation to the gate voltage application and IL species, and the magnitude of spectral changes was found to correlate positively with the drain current. Additionally, the Stark shifts of not only the organic semiconductor, but also of the IL on the organic semiconductor films were detected. This new method can be applied to other electrochemical devices such as organic thin film solar cells, in which the interfacial region is crucial to their functioning.

The role of solvent additive in metal nano-composite doped thin film organic solar cell

In this study, organic solar cells (OSCs) were designed using the solution processing method based on spin coating. The influence of solvent additive (1-chloronapthalene (CN)) and cadmium doped barium nitrate nanoparticle incorporated into the photoactive medium based on poly(3-hexylthiophene-2,5-diyl (P3HT): [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was investigated. The power conversion efficiency of the pristine device was compared to the power conversion efficiency of the devices fabricated with 30v% of 1- chloronapthalene and different weight concentrations of nanoparticles. An optimum efficiency of 3.55 % was attained at 0.3 wt.% with solvent additive compared to 3.25 % obtained for the pristine device. This increase is attributed to a rise in charge transport of 5.32 × 10−2 cm2V−1s−1. Further investigation on the morphological properties of the nanoparticles reveals the crystalline nature of the nanoparticle.

Progress on Organic Solar Cells: A Short Review

Thin film organic solar cells have emerged as a replacement to inorganic solar cells based on silicon. Organic solar cells offer several advantages compared to silicon-based devices. In the last 10 years, concentrated research attempts towards accomplishing the mandatory power conversion efficiency of 10 % and environmental stability of the device still remain a main challenge. In order to influence the efficiency, polymers are frequently utilized to fabricate the absorber and buffer layers. Also, binary and tenary polymer blends have been devised to influence the performance in micro/nanostructures. In addition, the advantages of organic solar cells for realistic application, and potential solutions are also considered.

In-Depth Analysis of Organic Solar Cells Using Transport Equation and Optical Transfer Matrix Method with Detailed Analytical Derivations

Thin-film organic solar cell (OSC) performances have been investigated in detail by improved analytical computation in this work. The generation of excitons inside OSC has been estimated by using the optical transfer matrix method (OTMM) to include the optical phenomena of the incident light. The dissociation of these excitons into free charge carriers has been investigated to find the most appropriate one. OSC performances have been evaluated by an improved analytical solution of electrical transport equations including (i) exciton generation obtained from OTMM, (ii) dissociation probability incorporating Gaussian distribution to account for the natural fact of the difference in photon-energy producing excitons, (iii) recombination of charge carriers, all together. OSC properties such as JSC, VOC, FF, PCE, Pmax, absorbance, and quantum efficiency have been investigated with the variation of different parameters; this might be useful to improve OSC. Again, the presented detailed derivations of analytical expressions would be helpful for clear understanding.

Synthesis and characterization of benzobisthiazole based polymers as donor materials for organic solar cells

Two conjugated polymers with (X-DADAD)n backbone and 2,6- or 4,8-linked benzobisthiazole (BBT) moieties were designed, synthesized and characterized as absorber materials in thin-film organic solar cells (OSCs). The 2,6-BBT polymer (P1) delivered enhanced short circuit densities and power conversion efficiencies in OSCs compared to devices based on 4,8-BBT polymer P2. Improved photovoltaic performance is related to the optimal morphology of P1/PC71BM blend films and higher and more balanced charge carrier mobilities.

Silver doped nickel oxide nanocomposite and photon harvesting enhancement in bulkheterojunction organic solar cell

Silver doped nickel oxide (Ag:NiOx) nanocomposites (NC) were synthesized using a thermal decomposition method for possible application in thin-film organic solar cells. Two different synthesis products were found from the experiment, which have exhibited different characteristics in terms of colour, structure, and optical properties. These nanocomposites (Ag:NiOx) have two distinct colours namely green and black. The green powder contains a trace of carbon element while the black powder is pure Ag:NiOx. Both products were used in device fabrication to assist in photons harvesting at a various concentration of the NC by weight. In all cases, an optimum concentration of 1 wt% of the Ag:NiOx powders were found to yield a maximum power conversion efficiency (PCE) of 4.9% and 5.1% for the green and black powders, respectively. Higher concentrations of Ag:NiOx in the solar absorber layers were found to be unfavorable in improving device performances. Overall, both synthesized metal NCs performed fairly similar and they have improved device performance substantially compared to the reference cells. The experimental results are discussed in terms of optical and electrical properties of the absorber layer as well as charge transport processes.

Local surface plasmon resonance assisted energy harvesting in thin film organic solar cells

Nickel sulfide(NiS) nano-particles are used in the solar absorber medium of thin film organic solar cell (TFOSC) to aid in harvesting solar energy. Solution-processed TFOSCs were fabricated using poly-3-hexylthiophene (P3HT) and (6-6) phenyl-C61-butyric acid methyl ester (PCBM) blend photo-active layer with or without NiS nano-particles(NPs). The new solar cells showed enhanced opto-electronic properties by the incorporation of NPs. The experimental data suggest that the device performances have been influenced by the concentration of NiS nano-particles in the absorber layer. Consequently, the power conversion efficiency(PCE) of the solar cell has improved by 93% from the reference cell, at 1% optimum concentration of NiS by weight. The best PCE recorded in this investigation was 4.63%, which is an important development in an ambient environment preparation condition. The effect of the metal nano-particles clearly demonstrated in this investigation in terms of enhanced short circuit current (Jsc) and PCE, which are an indicators of improved exciton dissociation and charge transportation processes in the medium. The results will be discussed by way of optical and electrical properties of the solar absorber films.