Special Section on Solution-Processable Organic Solar Cells

Ultimate form freedom in thin film solar cells by postmanufacture laser-based processing

[+] Author Affiliations
Jan Gilot

Holst Centre-Solliance, High Tech Campus 21, Eindhoven 5656 AE, The Netherlands

Baptiste Emelin

Holst Centre-Solliance, High Tech Campus 21, Eindhoven 5656 AE, The Netherlands

Yulia Galagan

Holst Centre-Solliance, High Tech Campus 21, Eindhoven 5656 AE, The Netherlands

Rajesh Mandamparambil

Holst Centre-Solliance, High Tech Campus 21, Eindhoven 5656 AE, The Netherlands

Ronn Andriessen

Holst Centre-Solliance, High Tech Campus 21, Eindhoven 5656 AE, The Netherlands

J. Photon. Energy. 5(1), 057210 (Jan 21, 2015). doi:10.1117/1.JPE.5.057210
History: Received October 31, 2014; Accepted December 18, 2014
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Abstract.  Thin film photovoltaics can be beneficial for specific applications like building integrated photovoltaics. To fully exploit the differentiator of form freedom, the interconnections in thin film modules can be tuned depending on the required module output. Traditionally, an alternation of coating and scribing steps is applied, determining the form from the start. Here, we present a set of techniques to define the module design from a master substrate with homogeneously coated electroactive layers. By applying subtractive and additive laser-based processes, the size and form of the module are only fixed after the manufacturing of the whole solar cell stack. By laser-induced forward transfer, an isolating dielectric material and a conductive top electrode are deposited in laser ablated scribes to enable the interconnection between two adjacent cells. After optimization of the laser settings for ablation and forward transfer, the optimal annealing time and temperature for the curing of the silver top electrode were determined. The proof of principle was demonstrated by constructing a 4-cell organic solar module of 1.0% efficiency on an area of over 3cm2 showing the anticipated short-circuit current and open-circuit voltage.

Figures in this Article

The installed capacity of photovoltaics is expanding year by year with more than 38 GW in 2013 worldwide.1 This market is dominated by silicon-based solar cells for rooftop and utility scale applications. The economy of scale of similar sized solar modules has tremendously reduced the price over the past years to facilitate such a large uptake of photovoltaics for grid connected power generation. In the future, new markets will be explored to integrate solar cells where fixed dimensions of modules can become a showstopper. In, for example, building integrated photovoltaics and automotive applications, esthetics and dimension freedom will determine the chance of success. For these applications, thin film photovoltaics will have an added value with a larger degree of flexibility in size and shape.

One of the thin film technologies outstanding in flexibility is organic photovoltaics (OPV). By roll-to-roll printing and coating techniques, OPV has shown great potential for the high-throughput production of cheap solar cells.24 The width of the substrate in combination with the type of substrate (plastic foil, glass, metal, etc…) already gives some freedom in size.5 Additionally, freedom can come from the interconnection of different cells into modules.

Traditional interconnection in thin film photovoltaics is done with the alternation of scribing (laser or mechanical) and coating.6 The first scribe removes a part of the bottom electrode and separates the bottom electrodes of the different cells. The second scribe clears the bottom electrode from the above deposited electroactive layers to enable a series connection with the top electrode of the adjacent cell. The third scribe removes a part of the top electrode to separate the top electrodes of the different cells. This technique is perfect for predefined cell widths and module output because the variable stripe width enables fine tuning of the current/voltage output of a module.

On the other hand, to be able to anticipate the requirements of a specific application, both esthetically and in output, a new technique has to be developed to fulfill the on-demand modification of the module dimension at the final stage of manufacturing. In this case, all electroactive layers are homogeneously deposited on the substrate, irrelevant of the type of thin film photovoltaic technology or substrate used. After the deposition of all layers, the substrate is treated with subtractive and additive processes to create a module with dimensions according to the requirements.

The subtractive processes include laser-based ablation or mechanical scribing.7 The advantage of a postmanufacturing subtractive step compared to the traditional scribing is the avoidance of the creation of debris on each step of the ablation which is not desired for following the coating process and is not compatible with a clean-room environment. The additive processes often studied for use for the top electrode are based on printing (inkjet or screen).8 Printing of a structured back silver electrode is challenging because of issues with the resolution of printing and alignment.

Therefore, we investigate in this article the application of a technology for digitally depositing materials with high precision at a high speed. Laser-induced forward transfer (LIFT) is a very promising digital technique which allows for high resolution of printed features and has been successfully adopted for organic electronic devices.9,10 The basic working principle of LIFT is illustrated in Fig. 1. The LIFT process utilizes a focused laser beam to transfer a donor material coated on a laser wavelength transparent substrate to a receiver substrate kept in close proximity. The laser energy is absorbed by the thin donor material, which results in heating, melting, and vaporization, leading to the transfer of the material to the receiver substrate.

Graphic Jump LocationF1 :

A schematic diagram showing the working principle of laser-induced forward transfer (LIFT).

Laser transfer techniques find potential applications in the microelectronics industry as an alternative to the lithography processes to deposit with high precision patterns of various materials without degrading the desirable properties of the bulk material.11,12 The LIFT process was demonstrated for a very wide range of materials,1315 including silver nanoparticles inks.16,17

The perspective of a noncontact, drop-on-demand technology with a high precision at high speed is very promising for the development of solar modules with flexibility in dimensions after the manufacturing process. In this article, we report on the first solar module manufactured utilizing a combination of subtractive and additive laser-based processing technologies. We show a proof of concept on organic solar cells. However, the technique is applicable to all thin film photovoltaic technologies. This allows the production of a master substrate with electroactive layers, which can be customized for the size and shape of the module depending on the application at the very end.

To advance toward a full freedom of form and design making use of only laser-based processes, multiple steps were investigated at the very end in the processing of the organic solar cell. First, the subtractive steps to selectively ablate parts of the homogeneously deposited solar cell stack were studied to isolate cells from each other in the module (P1) and to open up the bottom electrode for contact with the top electrode of the adjacent cell (P2). Second, the additive steps to deposit the isolating dielectric material and the silver top electrode were explored using laser-induced forward transfer technology. Finally, the lessons learned on subtractive and additive steps were united to manufacture a module after the deposition of all electroactive layers excluding the top electrode.

Subtractive Laser Processing

After the homogeneous full area deposition of the electroactive layers [indium tin oxide (ITO), zinc oxide (ZnO), poly(3-hexylthiophene):[6,6]phenyl C61-butyric acid methyl ester (P3HT:PCBM), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT)] the sample requires structuring into cells and ultimately a module. The first step is to isolate the bottom electrode of two adjacent cells. In this case, such a P1 isolation is achieved by removal of all layers from the glass substrate. The second step is to free the bottom electrode to enable the contact of the top electrode of one cell with the bottom electrode of the next. In this way, a series connection of the two cells is realized. Here, this P2 opening is obtained by removal of ZnO, P3HT:PCBM, and PEDOT from the ITO electrode.

These two steps involve different ablation parameters to address the two different process steps. The laser scribes were carried out through the glass substrate illuminated from the back. In this way, a cleaner and better defined ablation is achieved focusing the energy at the interface between layers. Hereby, the material can be removed from a nonabsorbing substrate. Furthermore, after the ablation, gravity supports in diminishing the debris formation on the sample.

The first subtractive process to remove all layers (P1) uses the triple frequency 355-nm UV laser with a pulse length of 10 ps. With a pulse-to-pulse overlap of 80% at a pulse fluence of 1.91J/cm2, the laser incidents on the sample from the back of the substrate to simultaneously remove ITO, ZnO, P3HT:PCBM, and PEDOT with minimal glass substrate damage. For the second subtractive process, all layers except the bottom ITO electrode (P1) are removed by illumination for the back with the 355-nm picosecond laser. ZnO, P3HT:PCBM and PEDOT are removed with a pulse-to-pulse overlap of 25% at a pulse fluence of 0.16J/cm2. Figure 2 shows the subtractive laser processing graphically and by microscopic images.

Graphic Jump LocationF2 :

Subtractive laser processing steps toward module manufacturing. P1 and P2 ablation scribes are performed from the back to isolate the bottom electrode from two adjacent cells and to open the bottom electrode for series connection with the top electrode of the previous cell. The microscopic pictures show the difference between an opened glass and indium tin oxide (ITO) substrate.

Additive Laser Processing

After the subtractive laser processing to mark the individual cells, these cells have to be interconnected by a top electrode and external contacts have to be created. Furthermore, to prevent shorting in the P1 scribe, an isolating material has to be deposited in the scribe. Laser pulses can be utilized to deposit materials as well. LIFT is an additive laser technique which has shown a lot of potential in multi-material deposition.18 The deposition of higher solid content materials is the main advantage of this technique. This is normally not possible with techniques like ink jet printing. For preventing shorts in the module interconnection, LIFT of a dielectric paste is utilized. The dielectric paste provides the necessary electrical isolation required during the interconnection process.

To evaluate the optimal laser settings for LIFT of the dielectric paste, a fluence scan was performed where the fluence was gradually augmented. A single shot fluence scan was carried out to identify the threshold of proper droplet transfers. Subsequently, an overlap scan is performed at the best fluence to optimize the continuous deposition of dielectrics and Ag paste. Here, it is important that the deposited layer is closed and covers the whole glass substrate locally. In this way, an undesired connection between two cells in the module becomes impossible. Figure 3 shows an overview of a typical laser fluence scan from low to high (bottom to top in the picture) of deposited droplets of dielectric paste on an acceptor substrate and of a pulse-to-pulse overlap scan of the same laser fluence range. Finally, the 355-nm laser with a 10-ps laser beam width uses a pulse overlap 50% and a laser fluence of 0.16J/cm2 for the deposition of the dielectric material.

Graphic Jump LocationF3 :

(a) Overview of deposited droplets of dielectric paste for various laser fluence from 0.09 to 0.14J/cm2 (bottom to top). (b) Deposited continues tracks of dielectric material with a laser fluence range from 0.09 to 0.16J/cm2 (bottom to top) and a pulse to pulse overlap of 50%.

For creating the interconnections of the separated OPV cells and the external contacts, an Ag paste is deposited by LIFT. In a similar stepwise approach as for the dielectric paste, a LIFT process is developed for the Ag paste with the picosecond laser system with the fundamental wavelength of 1064 nm. Also here, after the evaluation of the fluence scan [Fig. 4(a)], a pulse-to-pulse overlap scan was performed to obtain closed, continuous Ag lines which serve as interconnections between the cells as well as the top electrode of the cells and the external contacts of the module. The optimal results were achieved with a fluence of 0.25J/cm2 and a pulse-to-pulse overlap of 30%. In Figs. 4(b) and 4(c), the cross-section profiles over a line of 200-μm width and 8-mm length are depicted. It is clear that the lines are closed over the whole length of the line with a height varying between 1 and 3μm.

Graphic Jump LocationF4 :

(a) Overview of the droplets of Ag paste deposited on an acceptor substrate from lower fluence (0.031J/cm2) to higher fluence of 0.365J/cm2 from left column to the right. (b) and (c) Height profiles of a line deposited with LIFT of Ag paste with optimal settings measured in cross section and parallel direction.

Module Manufacturing

With the subtractive and additive laser processes optimized for this stack design, the manufacturing of cells and modules was studied. As a first step, the functionality of the Ag deposited by LIFT was evaluated. After the deposition of the Ag paste, a controlled annealing is required for optimal performance in solar cells. For this, the annealing time and temperature are varied over a large range in functional solar cells.

From Fig. 5, one can see that there is a broad range of annealing time suitable for high performance solar cells between 30 and 75 s. The optimal annealing temperature is situated around 110°C with some spread in the data. The data are normalized to be able to compare the two optimization steps. The annealing temperature variation was executed with an inferior batch of samples. By coincidence, the optimization of one parameter was performed at an ideal value for the other. The annealing time was tested at 110°C and the annealing temperature was tested for 45 s. This makes the results of the parameter optimization very relevant. In the rest of the experiments, these values (110°C and 45 s) were continually applied.

Graphic Jump LocationF5 :

Variation in annealing time (a) and temperature (b) of organic solar cells with a Ag top electrode deposited by LIFT.

The functionality of the Ag top electrode deposited by LIFT was compared to other commonly applied deposition technologies, namely evaporation and screen printing. The latter was performed with the same ink as the LIFT to avoid uncertainties about the interaction of the ink with the previously deposited PEDOT layer. Figure 6 depicts the current density to voltage curves with and without illumination of the three different top electrodes. There is only a minor variation between all three devices showing high fill factors (FFs) (Table 1). From these results, it can be concluded that LIFT is a suitable technology for the deposition of the top electrode.

Graphic Jump LocationF6 :

Current density to voltage characteristics of solar cells with different top electrodes deposition techniques. LIFT of a Ag electrode on a ITO/ZnO/P3HT:PCBM/PEDOT solar cell stack is compared to evaporated and screen printed Ag top electrode.

Table Grahic Jump Location
Table 1Overview of performance parameters for solar cells with different top electrodes deposition techniques.

To enable the manufacturing of modules, the subtractive and additive laser processing is combined with the optimized annealing settings of the top electrode. After a close look at the interconnection area, it was opted to add an additional P2 scribe next to the current P1 and P2 scribes. When the Ag top electrode of one cell fills the P2 scribe and makes contact with the bottom ITO electrode of the other cell, it will also make contact with the highly conductive PEDOT on top. This PEDOT is so conductive that it forms the electrical connection between the top electrode of the one cell and the other cell, i.e., shorting the device. To prevent this issue, a second P2 scribe was created and also filled with isolating dielectric paste. In this way, there is no chance for the two top electrodes to be electrically in contact.

After the homogeneous deposition of ZnO, P3HT:PCBM, and PEDOT on a glass substrate covered with ITO, P1 and P2 laser ablation was applied to selectively free glass and ITO in the first step. Second, the isolation material was deposited with LIFT followed by the LIFT processing of the Ag top electrode. A patterned deposition of the Ag top electrode omits the requirement for an additional P3 scribe. Finally, the solar cell was finished with the annealing of the whole module for 45 s at 110°C. The different processing steps are shown in Fig. 7 combined with microscopic pictures of the sample after each processing step. The dead area of the interconnection in this proof of principle reaches to around 850μm. Further, improvement of alignment and optical resolution could bring the dead area down below 500μm.

Graphic Jump LocationF7 :

Different laser-based processing steps of a module. Step 1 is the subtractive laser processing of P1 and P2 scribes to open up the glass and ITO layer. Step 2 is the additive laser processing with LIFT of the isolating dielectric material to prevent undesired electrical contacting between two cells in a module. Step 3 is the additive laser processing with LIFT of the Ag top electrode ensuring the interconnection between two cells. Below each step the microscopic picture of the step is shown.

The manufactured module consisted of four different cells with a total area of 3.13cm2. This module has a geometrical FF of 85%. The current density to voltage characteristics is shown in Fig. 8 and the performance parameters are summarized in Table 2. The module reaches the expected open-circuit voltage of 2.18 V which matches four times the open-circuit voltage of a P3HT:PCBM cell (0.54 V). The current of the module (4.7 mA) corresponds to the current density of the smallest cell (0.63cm2) of 7.5mA/cm2, which is very close to the current density of an individual cell (cf. Table 1). The FF (31%) is below expectations. This can originate from the relatively high sheet resistance of the Ag top electrode being insufficient to extract all charges without resistive losses because the width of the cells in the modules exceeds the width of the individual cells tested before. A further optimization of the curing procedure of the Ag could help to lower sheet resistance and losses by the series resistance. All in all, the performance of the module processed with homogeneous layers combined with subtractive and additive laser processing shows an efficiency of 1.0%. This result proofs the concept and shows the way to form freedom processing of a master substrate with homogeneously deposited electroactive layers.

Graphic Jump LocationF8 :

Current density to voltage characteristics of an organic solar module where homogeneous deposition of the layers is combined with subtractive and additive laser processing steps.

Table Grahic Jump Location
Table 2Overview of performance parameters for an organic solar module where homogeneous deposition of the layers is combined with subtractive and additive laser processing steps.

To make optimal use of the potential freedom in form and design of organic solar modules, a technique was developed to process the interconnection between different cells after the deposition of the layers. The electroactive layers excluding the top electrode were homogeneously deposited as a master substrate. Subsequently, the patterning and the deposition of the top electrode were performed with laser-based processes.

The different subtractive and additive laser processes were step by step optimized on an ITO/ZnO/P3HT:PCBM/PEDOT solar cell stack. Selective ablations for a P1 and P2 scribe were studied, followed by LIFT of isolating dielectric and conductive Ag pastes. The LIFT top electrode showed comparable performance in solar cells to evaporated or screen-printed Ag top electrodes after optimization of the annealing time and temperature.

The final module showed the expected values for open-circuit voltage and current. With a lower FF influenced by the sheet resistance, the overall performance still reached 1.0%. This example will pave the way toward form freedom with postprocessing techniques.

All device fabrication steps were performed under CR1000 conditions. Glass slides with patterned ITO (Naranjo, 130-nm thickness, 0.09cm2 active area) were cleaned in several rinsing steps, including ultrasound treatment with Teepol industrial detergent, deionized water, and isopropanol. The following stack was used as a reference: ZnO nanoparticles were synthesized according to 19 using the hydrothermal condensation of Zn(acetate). After several rinsing steps, the nanoparticles were redispersed in acetone and applied by spin coating (1000, 5000rpm/s, 60 s). The photoactive layer was spin coated from a 2 wt.%:2 wt.% poly-(3-hexylthiophene) (P3HT, Plextronics, Plexcore Mw 120kg/mol):[6,6] phenyl C61-butyric acid methyl ester (PCBM, 99%, Nano-C) (P3HT:PCBM) solution in chlorobenzene (550, 2000rpm/s, 95 s). The resulting ZnO and P3HT:PCBM layer thicknesses were approximately 50 and 220 nm, respectively. PEDOT:PSS (PEDOT, Agfa, Orgacon S315) was spin coated at 2000, 2040rpm/s for 60 s to form a 50-nm thick layer. The devices were annealed at 130°C for 10 min in a N2 atmosphere.

The evaporated Ag top electrode was applied by thermal evaporation resulting in a thickness of 100 nm. The dielectric paste (DuPont 5036 all-purpose thermal cure dielectric) and the Ag paste (Agfa, SI-P1000x) were primarily doctor bladed with a thickness of 20μm on a donor glass substrate. Subsequently, the material was transferred into the acceptor solar device over a distance of approximately 1 mm.

The laser used for the ablation and forward transfer processes is a Nd:YAG: Coherent Talisker picosecond laser which provides fundamental (1064 nm), frequency double (532 nm) and frequency tripled (355 nm) wavelengths. For focusing the laser beam on to the substrate surface, a long 580-mm focal length lens is used.

Layer thicknesses were obtained by Dektak profilometry. Current density to voltage curves were measured using simulated solar light in a home built set-up with a halogen lamp (100mW/cm2) calibrated with a Si reference cell and using a shadow mask. Power conversion efficiencies were calculated using the short-circuit current density obtained from the external quantum efficiency measurement.

Masson  G., Orlandi  S., Rekinger  M., Global Market Outlook For Photovoltaics 2014–2018. ,  EPIA ,  Belgium  (2014).
Mulligan  C. J. et al., “A projection of commercial-scale organic photovoltaic module costs,” Sol. Energy Mater. Sol. Cells. 120, (Part A ), 9 –17 (2014). 0927-0248 CrossRef
Søndergaard  R. et al., “Roll-to-roll fabrication of polymer solar cells,” Mater. Today. 15, , 36 –49 (2012). 0096-4867 CrossRef
Espinosa  N. et al., “Life cycle assessment of ITO-free flexible polymer solar cells prepared by roll-to-roll coating and printing,” Sol. Energy Mater. Sol. Cells. 97, , 3 –13 (2012). 0927-0248 CrossRef
Galagan  Y. et al., “Large area ITO-free organic solar cells on steel substrate,” Org. Electron.. 13, , 3310 –3314 (2012). 1566-1199 CrossRef
Kubis  P. et al., “High precision processing of flexible P3HT/PCBM modules with geometric fill factor over 95%,” Org. Electron.. 15, , 2256 –2263 (2014). 1566-1199 CrossRef
Gehlhaar  R. et al., “Four-terminal organic solar cell modules with increased annual energy yield,” Proc. SPIE. 8830, , 88300I  (2013). 0277-786X CrossRef
Galagan  Y. et al., “Technology development for roll-to-roll production of organic photovoltaics,” Chem. Eng. Proc.. 50, , 454 –461 (2011). 0255-2701 CrossRef
Biver  E. et al., “Multi-jets formation using laser forward transfer,” Appl. Surf. Sci.. 302, , 153 –158 (2014). 0169-4332 CrossRef
Biver  E. et al., “High-speed multi-jets printing using laser forward transfer: time-resolved study of the ejection dynamics,” Opt. Express. 22, , 17122 –17134 (2014). 1094-4087 CrossRef
Piqué  A., “Laser transfer techniques for digital microfabrication,” in Laser Precision Microfabrication. , Sugioka  K., Meunier  M., Piqué  A., Eds., pp. 259 –291,  Springer, Berlin Heidelberg ,  Germany  (2010).
Majumdar  J. D., Manna  I., “Laser processing of materials,” Sadhana. 28, , 495 –562 (2003). 0256-2499 CrossRef
Germain  C. et al., “Electrodes for microfluidic devices produced by laser induced forward transfer,” Appl. Surf. Sci.. 253, , 8328 –8333 (2007). 0169-4332 CrossRef
Nagel  M., Lippert  T., “Laser-induced forward transfer for the fabrication of devices,” in Nanomaterials: Processing and Characterization with Lasers. , Singh  S. C., Zeng  H. B., Guo  C., Cai  W., Eds., pp. 255 –316,  Wiley ,  Chichester, United Kingdom  (2012).
Yang  L. et al., “Microdroplet deposition of copper film by femtosecond laser-induced forward transfer,” Appl. Phys. Lett.. 89, , 161110  (2006). 0003-6951 CrossRef
Rapp  L. et al., “Pulsed-laser printing of silver nanoparticles ink: control of morphological properties,” Opt. Express. 19, , 21563 –21574 (2011). 1094-4087 CrossRef
Rapp  L. et al., “High-speed laser printing of silver nanoparticles ink,” J. Laser Micro Nanoeng.. 9, , 5 –9 (2014). 1880-0688 CrossRef
Perinchery  S. M. et al., “Investigation of the effects of LIFT printing with a KrF-excimer laser on thermally sensitive electrically conductive adhesives,” Laser Phys.. 24, , 066101  (2014). 1054-660X CrossRef
Beek  W. J. E. et al., “Hybrid zinc oxide conjugated polymer bulk heterojunction solar cells,” J. Phys. Chem. B. 109, , 9505 –9516 (2005). 1520-6106 CrossRef

Jan Gilot is a senior research scientist on organic photovoltaics at the Holst Centre (TNO department for flexible organic electronics) and Solliance, the collaborative initiative for thin film photovoltaic research in the ELAT region. He received his MSc degree in chemical engineering in 2006 and his PhD degree in physical chemistry in 2010 from the University of Technology Eindhoven for his work on polymer tandem solar cells. His current research interests include upscaling technologies for organic photovoltaics (OPV).

Baptiste Emelin: biography is not available.

Yulia Galagan is a senior scientist at Holst Centre. She received her PhD degree in chemistry in 2002 from Kyiv University. Her research interests include organic electronics. She joined the Holst Centre in 2008. Currently, she is responsible for the development of manufacturing technology for roll-to-roll processing of organic photovoltaics.

Rajesh Mandamparambil received his PhD degree in 2006 for the development of high gain polymer optical fiber amplifiers in the visible regime from Cochin University of Science and Technology, India. He then moved to City University London as a postdoctoral researcher developing fiber optical sensors until 2008. In 2008, he joined the TNO/Holst Centre, The Netherlands. His main research interests include laser deposition of sensitive materials and subtractive laser processing of thin films.

Ronn Andriessen is the manager of the organic photovoltaics program at Holst Centre and Solliance. He received his PhD in chemistry in 1991 from KU Leuven. Before joining Holst Centre, he was working as new business development manager of nanomaterials and polymer electronics at Agfa-Gevaert NV, Belgium. His current interests are the industrial manufacturing of solution-processed solar cells and the commercial applications thereof.

© The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Citation

Jan Gilot ; Baptiste Emelin ; Yulia Galagan ; Rajesh Mandamparambil and Ronn Andriessen
"Ultimate form freedom in thin film solar cells by postmanufacture laser-based processing", J. Photon. Energy. 5(1), 057210 (Jan 21, 2015). ; http://dx.doi.org/10.1117/1.JPE.5.057210


Figures

Graphic Jump LocationF1 :

A schematic diagram showing the working principle of laser-induced forward transfer (LIFT).

Graphic Jump LocationF6 :

Current density to voltage characteristics of solar cells with different top electrodes deposition techniques. LIFT of a Ag electrode on a ITO/ZnO/P3HT:PCBM/PEDOT solar cell stack is compared to evaporated and screen printed Ag top electrode.

Graphic Jump LocationF5 :

Variation in annealing time (a) and temperature (b) of organic solar cells with a Ag top electrode deposited by LIFT.

Graphic Jump LocationF4 :

(a) Overview of the droplets of Ag paste deposited on an acceptor substrate from lower fluence (0.031J/cm2) to higher fluence of 0.365J/cm2 from left column to the right. (b) and (c) Height profiles of a line deposited with LIFT of Ag paste with optimal settings measured in cross section and parallel direction.

Graphic Jump LocationF3 :

(a) Overview of deposited droplets of dielectric paste for various laser fluence from 0.09 to 0.14J/cm2 (bottom to top). (b) Deposited continues tracks of dielectric material with a laser fluence range from 0.09 to 0.16J/cm2 (bottom to top) and a pulse to pulse overlap of 50%.

Graphic Jump LocationF2 :

Subtractive laser processing steps toward module manufacturing. P1 and P2 ablation scribes are performed from the back to isolate the bottom electrode from two adjacent cells and to open the bottom electrode for series connection with the top electrode of the previous cell. The microscopic pictures show the difference between an opened glass and indium tin oxide (ITO) substrate.

Graphic Jump LocationF8 :

Current density to voltage characteristics of an organic solar module where homogeneous deposition of the layers is combined with subtractive and additive laser processing steps.

Graphic Jump LocationF7 :

Different laser-based processing steps of a module. Step 1 is the subtractive laser processing of P1 and P2 scribes to open up the glass and ITO layer. Step 2 is the additive laser processing with LIFT of the isolating dielectric material to prevent undesired electrical contacting between two cells in a module. Step 3 is the additive laser processing with LIFT of the Ag top electrode ensuring the interconnection between two cells. Below each step the microscopic picture of the step is shown.

Tables

Table Grahic Jump Location
Table 2Overview of performance parameters for an organic solar module where homogeneous deposition of the layers is combined with subtractive and additive laser processing steps.
Table Grahic Jump Location
Table 1Overview of performance parameters for solar cells with different top electrodes deposition techniques.

References

Masson  G., Orlandi  S., Rekinger  M., Global Market Outlook For Photovoltaics 2014–2018. ,  EPIA ,  Belgium  (2014).
Mulligan  C. J. et al., “A projection of commercial-scale organic photovoltaic module costs,” Sol. Energy Mater. Sol. Cells. 120, (Part A ), 9 –17 (2014). 0927-0248 CrossRef
Søndergaard  R. et al., “Roll-to-roll fabrication of polymer solar cells,” Mater. Today. 15, , 36 –49 (2012). 0096-4867 CrossRef
Espinosa  N. et al., “Life cycle assessment of ITO-free flexible polymer solar cells prepared by roll-to-roll coating and printing,” Sol. Energy Mater. Sol. Cells. 97, , 3 –13 (2012). 0927-0248 CrossRef
Galagan  Y. et al., “Large area ITO-free organic solar cells on steel substrate,” Org. Electron.. 13, , 3310 –3314 (2012). 1566-1199 CrossRef
Kubis  P. et al., “High precision processing of flexible P3HT/PCBM modules with geometric fill factor over 95%,” Org. Electron.. 15, , 2256 –2263 (2014). 1566-1199 CrossRef
Gehlhaar  R. et al., “Four-terminal organic solar cell modules with increased annual energy yield,” Proc. SPIE. 8830, , 88300I  (2013). 0277-786X CrossRef
Galagan  Y. et al., “Technology development for roll-to-roll production of organic photovoltaics,” Chem. Eng. Proc.. 50, , 454 –461 (2011). 0255-2701 CrossRef
Biver  E. et al., “Multi-jets formation using laser forward transfer,” Appl. Surf. Sci.. 302, , 153 –158 (2014). 0169-4332 CrossRef
Biver  E. et al., “High-speed multi-jets printing using laser forward transfer: time-resolved study of the ejection dynamics,” Opt. Express. 22, , 17122 –17134 (2014). 1094-4087 CrossRef
Piqué  A., “Laser transfer techniques for digital microfabrication,” in Laser Precision Microfabrication. , Sugioka  K., Meunier  M., Piqué  A., Eds., pp. 259 –291,  Springer, Berlin Heidelberg ,  Germany  (2010).
Majumdar  J. D., Manna  I., “Laser processing of materials,” Sadhana. 28, , 495 –562 (2003). 0256-2499 CrossRef
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