Illustration of the screen printing process (above) and examples of the laboratory screen printer (below-left) and the industrial screen printer (below-right). (c) diagrammatic portrayal of sputter deposition of exfoliated graphene (EG) dispersion on poly(ethylene 2,6-naphthalene) (PEN); (d) J-V properties of the cell under dark (dashed line) and light (solid line) conditions. a) Schematic description of PSC with G anode and G/ structure.
INTRODUCTION TO ORGANIC SOLAR CELLS
CONTENTS
CHAPTER
INTRODUCTION
- Solar Energy
- Organic Solar Cells (SCs)
- Overview of Organic Semiconductors
- Structure of Organic Solar Cell
Unlike OLEDs, OSCs use organic semiconductors to absorb light and transform it into electricity (Brabec et al., 2002a, b). LUMO and HOMO of organic semiconductors imply hybridization between antibonding and bonding of conjugated p-electrons (Bredas et al., 2002; . Kymissis, 2009).
CHARACTERISTICS OF ORGANIC SOLAR CELLS (SCS)CELLS (SCS)
- Organic Solar or Photovoltaic (PV) Materials
- Advantages of Flexible Organic Compared to Rigid Con- ventional Solar Cells (SCs)
- Manufacturing Process and Cost
- Tailoring Molecular Properties
- Desirable Properties
- Environmental Impact
- Multiple Uses and Applications
Organic SCs could be easily fabricated compared to silicon-made cells, and this is due to the molecular nature of the materials used. The current situation shows that organic SCs cannot exchange with silicon cells in the energy transformation field.
THE CURRENT SITUATION
- Exciton Diffusion and Dissociation
- Carrier Transport
- Charge Extraction at Electrodes
- Summary of the Operation
- Bulk Heterojunction (BHJ) Solar Cells (SCs)
- Tandem Solar Cells (SCs)
The drive current corresponds to the movement of the carrier along the potential gradient inside the solar cell. The creation of the heterojunction by Tang et al. 1986) was initially demonstrated in the type of a double layer solar cell.
CHARACTERIZATION OF ORGANIC SOLAR CELLS (SCS)CELLS (SCS)
- J-V Characteristics
- Incident Photon to Electron Conversion Efficiency (IPCE) J-V characteristics only are not enough to fully characterize a solar cell,
FF means the dependence of the current output on the internal field of the device and is measured by the shunt resistance and series resistance. The shape of the IPCE curve is highly dependent on the absorption curve of the active layer.
Performance improvement of polymeric solar cells by using a solvent-treated poly(3,4-ethylenedioxythiophene), poly(styrene sulfonate) buffer layer. Characterization of the mesoscopic structure in the photoactive layer of organic solar cells: a focused overview.
POLYMERIC MATERIALS FOR SOLAR CELLS
INTRODUCTION
In polymer SCs, the dynamic layers of the device must be positioned between 2 conductive electrode layers, one of which is crystal clear to the incident light (Gopinath et al., 2019). In OSCs of this type, the D-A interface, which enters the entire volume of the material, ensures the dissociation of excitons, as well as the transport of holes and electrons to the electrodes (Kim et al.
DESCRIPTION OF NOVEL ORGANIC MATERIALSMATERIALS
Nevertheless, the actual efficiency value for an organic solar cell based on P3HT:[60]PCBM does not exceed 5% (Dennler et al., 2009). Such polymers must have a bandgap (difference in HOMO and LUMO (lowest unoccupied molecular orbital) energies) of less than 2 eV (Al-Ibrahim et al., 2005). The optoelectronic enhancement is therefore attributed to the block copolymer inherent molecular self-assembly and nanophase morphology, resulting in reduced carrier and exciton losses (Antoniadis et al., 1993; Biglova et al., 2017).
FULLERENE-CONTAINING POLYMERS FOR ORGANIC SOLAR CELLS (SCS)ORGANIC SOLAR CELLS (SCS)
Also of interest are the numerous works in which FCMs (monomers containing fullerenes) were subjected to metathesis polymerization using a Grubbs catalyst and the products were verified in SC (Torosyan et al., 2014). In both circumstances, polymer precipitation and consumption of starting norbornenes 1–3 (TLC monitoring) were observed for the first 3 h ( Yang et al., 2013 ). In all circumstances, metathesis polymerization results in the creation of copolymers 10, 11 (CHCl3, dimethyl sulfoxide) soluble in some organic solvents with good conversion rates (Salikhov et al., 2013b; . Benduhn et al., 2017) .
SOLUBLE FUNCTIONALIZED POLYANILINES
A relative analysis of the synthesized substances revealed that the extreme electrical conductivity was demonstrated by a polymer soluble in the maximum number of conventional solvents, which was far from the participation of sulfonic acids. We investigated the most effective representatives and expanded the range of electrically conductive high molecular weight compounds, mainly using functionalized aniline and investigating the physicochemical and electrophysical properties of the target products. The impact of the two reactions depends on the protonation state of the reactants and subsequently on the pH of the reaction medium (Günes et al., 2007; Krebs, 2008).
CHARGE TRANSPORT IN THIN POLYMER FILMS
In the works of Biglova et al. (2015), the temperature dependence of the electrical conductivity was calculated for films with different polyaniline shapes. In this situation, the barrier height is described by the difference between the electron affinity of the polymer and the work function of the metal. For efficient absorption in the observable part of the solar spectrum, the band gap should be between 1.4 and 1.5 eV (Salikhov et al., 2013a, b).
ORGANIC SOLAR CELLS (SCS) BASED ON THIN POLYMER FILMSPOLYMER FILMS
The CV characteristics (current-voltage characteristics) of all the finished OSC samples were calculated, and the numerical values of such parameters as short-circuit current, open-circuit voltage, PCE, and duty factor were calculated based on them. Calculation of the CV characteristics of a PV cell is usually done by exposing it to constant illumination and a recognized temperature. Therefore, it was demonstrated that a mixture of PANI with fullerene-containing polymers is very significant for the formation of OSC based on binary D-A systems.
POLYMERIZABLE METHANOFULLERENE AS A BUFFER LAYER MATERIAL FOR ORGANIC SOLAR
Zinc oxide: Conjugated polymer nanocomposite as cathodic buffer layer for solution-processed inverted organic solar cells. Open-circuit voltage origin of thin-film organic solar cells based on conjugated polymers. In-operando study of the effects of solvent additives on the stability of organic solar cells based on PTB7-Th: PC71BM.
DONOR MATERIALS FOR ORGANIC SOLAR CELLS
- INTRODUCTION
- PERFORMANCE PARAMETERS OF SCS (SOLAR CELLS)(SOLAR CELLS)
- SMDMS-CENTERED PHOTOVOLTAICS (PVS)
- OLIGOTHIOPHENE-CENTERED SMDMS
- OLIGOTHIOPHENE-BDT
The last era witnessed an amazing boom in the expansion of the high PCE (power conversion efficiency) OPV cells using organic donor materials. The pin is usually given by spectral intensity corresponding to the intensity of the sun on Earth at an angle of nearly 48.2° (Monestier et al., 2007; Jun et al., 2013). However, an important improvement in the PCE and some other parameters was observed with fluorination of the central thiophenes (Figure 3.3).
BENZODITHIOPHENE) HYBRIDS AS SMDMS
IDT (INDACENODITHIOPHENE)-CENTERED SMDMSSMDMS
Non-fullerene organic solar cells made from small molecules with a high fill factor and a high efficiency of more than 10%. Small molecule with low band gap for efficient organic solar cells with low energy loss underneath. Development of high-quality organic solar cells with small molecules via a large planar structure and an electron-withdrawing central unit.
ACCEPTORS MATERIALS FOR ORGANIC SOLAR CELLS
INTRODUCTION
Poly(3-cyano-4-hexylthiophene) and cyano-poly(phenylenevinylene) have been used as acceptors in OPV cells and show high electron affinity coming from the electron-withdrawing cyano (CN) groups in the vinylene group of poly( phenylenevinylene). ) or of the thiophene ring of polythiophene. A general growth trend of n-type polymer acceptors is given in this chapter (Parida et al., 2011; Dou et al., 2013). Based on this synthetic design rule, several low-bandgap combinatorial polymers have been produced and used as donors in polymer PV cells (Guo et al., 2013).
RYLENE DIIMIDE-CENTERED POLYMER ACCEPTORSACCEPTORS
- PDI-Centered Polymer Acceptors
- NDI-Centered Polymer Acceptors
- DTCDI-Centered Polymer Acceptors
Long ago, Sharma and colleagues developed the interchangeable phenylenevinylene and PDI copolymer 9 (Figure 4.2) via Heck coupling for use as an acceptor in the BHJ SCs (Mikroyannidis et al., 2009; Liang et al., 2011). . The polymer acceptors showed broad absorption in the range (350 to 850 nanometers) and with an optical band gap of almost 1.46 eV. The device performance parameters and photophysical properties of DTCDI-centered polymer acceptors (25) are given in the literature.
FLUORENE AND BT-CENTERED POLYMER ACCEPTORSACCEPTORS
A PCE of 2.0% was achieved in the mixture using chloroform, higher than that achieved using o-dichlorobenzene or CB. The highest PCE of 2.7% and FF value of 0.55 were achieved with high molecular weight polymer 28 and donor D1 in BHJ SC due to enhanced electron and hole transport. The use of BCP created well-managed D-A interfaces that enabled the best BHJ SC performance among devices involving BT-centered n-type fluorenes and polymers.
CN-REPLACED POLYMER ACCEPTORS
The PCE was improved by curing the finished devices, and the improvement in hole mobility after curing was attributed to the enhanced molecular ordering of polymers and a red-shifted optical absorption of blended films. The device using the mixture showed higher PCE compared to that of the double-layer devices, and the device performance was improved by annealing due to the increased ordering of chains in the D16. Strong absorption bands were noted for all polymers, and the red-shift of the absorption spectra was induced by increasing the number of thiophene units in the polymer.
OTHER POLYMER ACCEPTORS COMPRISING ELECTRON-REMOVING UNITSELECTRON-REMOVING UNITS
The unit of DPP is the strong removal unit, and the DPP-centered D-A type polymer and the small molecule materials for donors have shown promising performances in the BHJ SCs. The mixing ratio of 1:0.45 (donor:acceptor, w/w) was suitable for the BHJ SCs, and the open-circuit voltage values were similar despite the variation in the ratio of 44. Relatively low power conversion efficiency (maximum of 0.07%) was obtained with this kind of species; conversely, research is ongoing and the range of several possibilities for developing new polymer acceptors remains open (Kymakis et al., 2006).
SUMMARY
All-polymer solar cells based on side-chain-isolated polythiophenes and poly(perylene diimidealt-dithienothiophenes). All-polymer solar cells based on fully conjugated block copolymers composed of poly(3-hexylthiophene) and poly(naphthalene bisimide) segments. Efficient all-polymer solar cells based on a mixture of tris(thienylenevinylene)-substituted polythiophene and poly[perylene diimide-alt-bis(dithienothiophene)].
FABRICATION TECHNIQUES FOR ORGANIC SOLAR CELLS
INTRODUCTION
In terms of structure, unit efforts have been relatively limited for several reasons (Coakley and McGehee, 2004; Zhao et al., 2008). The most important step is certainly the stacking of the low and high bandgap materials in tandem SC with the highest reported PCE of 6.5%. An example of the tandem SC structure is shown in Figure 5.1 together with instances of low and high band gap materials (Coakley et al., 2005; You et al., 2013).
THE MERGER CHALLENGE
Therefore, it is reasonable to assume that this very limited selection in device geometry has had some influence both on the choices made during the engineering of the new materials and on an observed state of the art. Good cases are implying each zone and some cases involving 2 of the zones, but in general, there has been no news of a significant way out so that all zones can be covered. There has been a current curiosity about the operational stability of equipment and more about accepting why materials and equipment fail (Jørgensen et al., 2008; Thompson and Fréchet, 2008).
TYPICAL STRUCTURE OF A DEVICE
THE SEA OF FILM-FORMING METHODS
Therefore, one of the current tests is to identify perfect coating methods for polymeric SCs. Finally, some coating methods allow the creation of multilayer films in a similar coating step. This is very good for general printing and coating where pattern transfer is required.
COATING AND PRINTING METHODS
- Casting
- Spin Coating
- Doctor Blading
- Screen Printing
- Inkjet Printing
- Pad Printing
The performance of the spin-coating technique within polymer PVs is understandable, despite its inefficient nature. The first developments in the screen printing technique date back to the beginning of the 20th century. The printing method is relatively complex and is centered on the creation of the small drop of ink, which is then placed on the substrate (Krebs et al., 2005).
PATTERNING AND JUXTAPOSITION OF THE MULTILAYER FILMSMULTILAYER FILMS
- Zero-Dimension Coating
The layer deposition sequence and positions (top) are shown, along with the associated input of aperture loss when two cells are connected in series. In the easiest circumstances for instant slot coating, the stripe pattern on top of the stripe pattern present on the substrate is suitable for simple decoding of the slot deposition head in a direction perpendicular to the tape direction (Nomura et al. ., 2016; . Abbel et al., 2018). In intermediate circumstances such as screen printing, it is normal to encounter markings that allow the screen to change in directions along and perpendicular to the direction of the web.
ROLL-TO-ROLL (R2R) METHODS
A completely raw substrate must enter the processing machine at one end and the final flexible SC polymer must emerge at the other end of the machine.
OTHER TECHNIQUES
Production of large area polymer solar cells by industrial screen printing, lifetime considerations and lamination with polyethylene terephthalate. A complete process for the production of large-area flexible polymer solar cells exclusively by screen printing-first public demonstration. Spontaneous open-circuit voltage enhancement of fully fabricated organic solar cells caused by elimination of interfacial energy perturbations.
INTRODUCTION
