Laser processing of organic photovoltaic cells with a roll-to-roll manufacturing process

Petsch, Tino; Haenel, Jens; Clair, Maurice; Keiper, Bernd; Scholz, Christian

doi:10.1117/12.876245

Cited by 17 publications

(14 citation statements)

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“…The procedure was to first calculate the loss due to the distributed PEDOT resistance and only the shadow loss induced by the gridlines, where the program returned the new JV curves of the devices with 1,2,3,4,6,8,10, and 20 fingers (Figure 2). These JV curves were then used as input to calculate the ohmic loss due to the distributed resistance in the silver lines.…”

Section: Resultsmentioning

confidence: 99%

Current Collecting Grids for ITO‐Free Solar Cells

Galagan

Zimmermann

Coenen³

et al. 2011

Advanced Energy Materials

120

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Indium-tin-oxide (ITO) free polymer solar cells prepared by ink jet printing a composite front electrode comprising silver grid lines and a semitransparent PEDOT:PSS conductor are demonstrated. The effect of grid line density is explored for a large series of devices and a careful modeling study enabling the identification of the most rational grid structure is presented. Both optical and light beam induced current (LBIC) mapping of the devices are used to support the power loss model and to follow the evolution of the performance over time. Current generation is found to be evenly distributed over the active area initially progressing to a larger graduation in areas with different performance. Over time coating defects also become much more apparent in the LBIC images. Results and DiscussionA series of large area (2 cm × 2 cm) ITO-free organic solar cell devices were prepared on glass substrates (Figure 1). The devices contained current collecting grids/high conductivity PEDOT:PSS/P3HT:PCBM/LiF:Al. A schematic illustration of the devices is shown in Figure 1a. Current collecting grids are represented as parallel lines with different spacing (pitch size) ( Figure 1b). The devices with pitch sizes of 20, 10, 6.7, 5, 3.3, 2.5, 2, and 1 mm were prepared. The pitch size is defined as the distance between the centers of two neighboring grid lines. The number of the grid lines in the devices was changed as 1, 2, 3, 4, 6, 8, 10, and 20, respectively. The width of the grid lines was constant for each batch of devices. Thus shadowing losses increase with the number of grid lines. The effect of different pitch for the grid fingers was calculated at Fraunhofer ISE using a one dimensional numerical model developed by Glatthaar et al. [37,38] Each infinitesimal cell element with width dx delivers the current j(V(x))dx. The function j(V) is given by the current-voltage (JV)-curve of a small area device. Starting from x = 0 the current sums up to I(x) (Equation 1). This current leads to a voltage drop in the current collecting electrode corresponding to Ohm´s law (Equation 2), with ρ being the sheet resistance of the electrode(s). As the current output from the infinitesimal cell elements depends on the voltage V(x) at position x, also the current density j(V(x)) depends on the position x. Therefore the two differential Equations 1 and 2 are coupled:with the boundary conditions V (x = 0) = V 0 and I(x = 0) = 0.The area loss, which in a one dimensional model is the length l loss due to coverage with grid fingers or dead area due to series circuitry is accounted for by integrating the current I from 0 to the length of the active area l active but normalizing the current to the length including the lost "area" l active + l loss . The JV curve of the grid cell or module respectively therefore is given by:The model was used to consecutively calculate the ohmic and area losses in the PEDOT layer and metal fingers. The procedure was to first calculate the loss due to the distributed PEDOT resistance and only the shadow loss induced...

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Section: Resultsmentioning

confidence: 99%

Current Collecting Grids for ITO‐Free Solar Cells

Galagan

Zimmermann

Coenen³

et al. 2011

Advanced Energy Materials

120

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“…With traditional laser etching, the smallest negative features that could be achieved were ∼20 μm, with another 2−3 μm of the polymer showing clear signs of degradation, dewetting, melting, and removal. 35 Recently, Mouléet al have developed a novel patterning technique, called dopant-induced solubility control (DISC), based on the observation that the solubilities of some semiconducting polymers, for example, the prototypical semiconducting polymer regioregular poly(3-hexylthiophene) (P3HT), can be reversibly controlled by doping with high electron affinity molecules (such as the molecular dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ)). 1−3 The solubility reduction of the semiconducting polymer upon doping is believed to result from the formation of the ionic salt complex, [polymer + ]:[dopant − ], which is not soluble in nonpolar solvents.…”

Section: ■ Introductionmentioning

confidence: 99%

High-Speed Photothermal Patterning of Doped Polymer Films

Bedolla-Valdez

Wang

et al. 2019

ACS Appl. Mater. Interfaces

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Organic semiconductors (OSCs) offer a new avenue to the next-generation electronics, but the lack of a scalable and inexpensive nanoscale patterning/deposition technique still limits their use in electronic applications. Recently, a new lithographic etching technique has been introduced that uses molecular dopants to reduce semiconducting polymer solubility in solvents and a direct-write laser to remove dopants locally, enabling rapid OSC etching with diffraction limited resolution. Previous publications postulated that the reaction that enables patterning is a photochemical reaction between photoexcited dopants with neutral solvent molecules. In this work, we analyze the photoinduced dissolution kinetics of F4TCNQ doped P3HT films using time-resolved in situ optical probing. We find two competing mechanisms that control de-doping and dissolution: the first is the photochemical reaction posited in the literature, and the second involves direct heating of the polymer by the laser, inducing increased solubility for both the polymer and dopant. We show that the wavelength-specific photochemical effect is dominant in low photon doses while the photothermal effect is dominant with high excitation rates regardless of laser wavelength. With sufficiently high optical intensity input, the photothermal mechanism can in principle achieve a high writing speed up to 1 m/s. Our findings bring new insights into the mechanisms behind laser direct writing of OSCs based on dopant induced solubility control and enable ultraprecise fabrications of various device configurations in large-scale manufacturing.

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“…Therefore, 1064 nm wavelength in the NIR region is selected in this study due to its wide industrial availability. It is noteworthy that this is different from previous works, in which 520 nm wavelength in visible region was reported for organic layer ablation while the 1064 nm was not recommended due to the elusive process window for clear ablation and the terrible edge bulge of up to hundreds of nanometers . The reason for this departure is mainly due to the different ablation mechanisms between the conventional vaporization methods and the LFT technique, which will be discussed below.…”

Section: Resultsmentioning

confidence: 99%

“Layer‐Filter Threshold” Technique for Near‐Infrared Laser Ablation in Organic Semiconductor Device Processing

Chen

Zhao

et al. 2015

Adv Funct Materials

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Although conventional laser ablation (CLA) method has widely been used in patterning of organic semiconductor thin films, its quality control still remains unsatisfied due to the ambiguous photochemical and photothermal processes. Based on industrial available near‐infrared laser source, herein, a novel “layer‐filter threshold” (LFT) technique is proposed, which involves the decomposition of targeted “layer‐filter” and subsequent explosive evaporation process to purge away the upper layers instead of layer‐by‐layer ablation. For photovoltaic device with structure of metal/blend/PEDOT:PSS/ITO/glass, the PEDOT:PSS layer as the “layer‐filter” is first demonstrated to be effective, and then the merged P1–P2 line and metal electrode layer are readily patterned through the “self‐aligned” effect and regulation of ablation direction, respectively. The correlation between laser fluence and explosive ablation efficacy is also investigated. Finally, photovoltaic modules based on classical P3HT:PC61BM and low‐bandgap PBDT‐TFQ:PC71BM systems are separately fabricated following the LFT technique. It is found that over 90% of geometric fill factor is achieved while device performances maintain in a limited change with increased number of series cells. In comparison to conventional laser ablation methods, the LFT technique does not require sophisticated instruments but reaches comparable processing accuracy, which shows promising potential in the fabrication and commercialization of organic semiconductor thin‐film devices.

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Laser processing of organic photovoltaic cells with a roll-to-roll manufacturing process

Cited by 17 publications

References 0 publications

Current Collecting Grids for ITO‐Free Solar Cells

Current Collecting Grids for ITO‐Free Solar Cells

High-Speed Photothermal Patterning of Doped Polymer Films

“Layer‐Filter Threshold” Technique for Near‐Infrared Laser Ablation in Organic Semiconductor Device Processing

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