Highly efficient polymer solar cells with printed photoactive layer: rational process transfer from spin-coating

103

The current work reports a high power conversion efficiency (PCE) of 9.54% achieved with nonfullerene organic solar cells (OSCs) based on PTB7‐Th donor and 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene) (ITIC) acceptor fabricated by doctor‐blade printing, which has the highest efficiency ever reported in printed nonfullerene OSCs. Furthermore, a high PCE of 7.6% is realized in flexible large‐area (2.03 cm2) indium tin oxide (ITO)‐free doctor‐bladed nonfullerene OSCs, which is higher than that (5.86%) of the spin‐coated counterpart. To understand the mechanism of the performance enhancement with doctor‐blade printing, the morphology, crystallinity, charge recombination, and transport of the active layers are investigated. These results suggest that the good performance of the doctor‐blade OSCs is attributed to a favorable nanoscale phase separation by incorporating 0.6 vol% of 1,8‐diiodooctane that prolongs the dynamic drying time of the doctor‐bladed active layer and contributes to the migration of ITIC molecules in the drying process. High PCE obtained in the flexible large‐area ITO‐free doctor‐bladed nonfullerene OSCs indicates the feasibility of doctor‐blade printing in large‐scale fullerene‐free OSC manufacturing. For the first time, the open‐circuit voltage is increased by 0.1 V when 1 vol% solvent additive is added, due to the vertical segregation of ITIC molecules during solvent evaporation.

“…For example, the comparable PCEs of fullerene-based OSCs prepared by doctor-blading and spin-coating techniques were reported by Zhao et al [16] The OSCs based on poly [4,8-…”

supporting

confidence: 61%

Printed Nonfullerene Organic Solar Cells with the Highest Efficiency of 9.5%

Lin

Jin

Dong

et al. 2018

103

“…

power conversion efficiency (PCE) of BHJ devices strongly depends on phase separation of the donor and acceptor. [21,22] Moreover, green solvent is a prerequisite for the commercialization of OSCs. To achieve high-performance devices, much effort has been devoted to delicately control the morphology of the active layer (such as the blend ratio between the donor and acceptor, [9][10][11] the type of solvent, [12][13][14] the type and amount of processing additive, [15][16][17] and thermal and solvent annealing [18][19][20] ) to obtain optimal interpenetrated nanoscale phase separation.

…”

mentioning

confidence: 99%

High‐Performance Large‐Area Organic Solar Cells Enabled by Sequential Bilayer Processing via Nonhalogenated Solvents

Dong

Zhang

Xie

et al. 2018

168

161

power conversion efficiency (PCE) of BHJ devices strongly depends on phase separation of the donor and acceptor. However, the formation of BHJ morphology is an extremely complicated process and the formed morphology is also a highly delicate balance involving many parameters such as domain size, purity, miscibility, etc. To achieve high-performance devices, much effort has been devoted to delicately control the morphology of the active layer (such as the blend ratio between the donor and acceptor, [9][10][11] the type of solvent, [12][13][14] the type and amount of processing additive, [15][16][17] and thermal and solvent annealing [18][19][20] ) to obtain optimal interpenetrated nanoscale phase separation. What is worse, the morphology control becomes much more challenging when the device area is scaled up, for example, the morphology of printed film may vary drastically when the processing condition changes. For this reason, there are typically large performance drops when OPV devices are scaled up to large area or processed using printing techniques. [21,22] Moreover, green solvent is a prerequisite for the commercialization of OSCs. However, for the BHJ structure, the solubility and miscibility of both the donor and acceptor must be taken into consideration together, which limits the selection of a processing solvent. Most OSCs were processed with toxic halogen solvents, and only a few high-performances donor/acceptor combinations were reported in the literature using low toxicity/nontoxic solvents.In contrast, sequential deposition of the donor and acceptor materials followed by post thermal annealing can lead to a similar BHJ morphology and reasonably efficient OSC devices. The interpenetration between donor and acceptor during the solution processing ensures the D/A interfaces for separation of the charges. [23][24][25] The bilayer structure should be more favorable for charge transport as the separated charges can easily transport to each electrode through the D or A layer with low possibility of recombination. [26][27][28] In addition, as both donor and acceptor layers can be processed and optimized independently, this bilayer structure should show less dependence on the D/A ratio, solvent, additive, etc., when compared with the BHJ structure. These properties make the bilayer structure very attractive for achieving high-performance OSCs and While the performance of laboratory-scale organic solar cells (OSCs) continues to grow over 13%, the development of high-efficiency large area OSCs still lags. One big challenge is that the formation of bulk heterojunction morphology is an extremely complicated process and the formed morphology is also a highly delicate balance involving many parameters such as domain size, purity, miscibility, etc. The morphology control becomes much more challenging when the device area is scaled up. In this work, a highly efficient (12.9%) nonfullerene organic solar cell processed using a sequential bilayer deposition method from nonhalogenated solvents, is reported. Using this bi...

“…[21] Although the abovementioned studies showed promising results, the blade coating method could have limited practicality in manufacturing, especially for roll-to-roll production, due to the method having difficulty in controlling film-thickness and fabricating stripe patterns; and in fact, there has been no report on the roll-to-roll fabrication of blade-coated PSCs. [43][44][45][46][47] Moreover, large fractions of highperformance materials are not suitable for roll-to-roll slot-die coating. The method is classified as a premetered method, so that the thickness of films can be easily and precisely controlled, simply by controlling the solution flow into the head.…”

mentioning

confidence: 99%

Slot‐Die and Roll‐to‐Roll Processed Single Junction Organic Photovoltaic Cells with the Highest Efficiency

Lee

Seo

Kwon

et al. 2019

PSC-efficiencies have increased with intensive effort on novel materials synthesis, film-morphology engineering, and interface control, and the state-of-the-art PSCs have eventually produced a high power conversion efficiency (PCE) of over 15%. [9][10][11][12][13][14][15][16][17][18][19][20][21] For example, Zou et al. reported a newly synthesized nonfullerene acceptor (NFA), Y6, having an electron-deficient-core-based fused ring with a benzothiadiazole unit, and the resulting single-junction PSCs based on PM6:Y6 BHJ showed an excellent efficiency of 15.7% and a certified PCE of 14.9%. [20] In addition, Hou and co-workers recently reported a series of copolymers, and in particular, the copolymer T1 (poly[(2,6-(4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)-benzo[1,2-b:4,5-b′] dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′] dithiophene-4,8-dione)] (PBDB-TF) = 0.8 and PTO2 = 0.2) produced the bestefficiency of 15.1% and certified PCE of 14.6% in PSCs using 3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6,7difluoro)-indanone))-5,5,11,11-tetrakis(4hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′] dithiophene (IT-4F) acceptor. [21] One of the representative routes to further enhance PSCefficiency is broadening the absorption bandwidth of the active film for better sunlight absorption. [21][22][23] To this end, the ternary The record efficiency of the state-of-the-art polymer solar cells (PSCs) is rapidly increasing, due to the discovery of high-performance photoactive donor and acceptor materials. However, strong questions remain as to whether such high-efficiency PSCs can be produced by scalable processes. This paper reports a high power conversion efficiency (PCE) of 13.5% achieved with single-junction ternary PSCs based on PTB7-Th, PC 71 BM, and COi8DFIC fabricated by slot-die coating, which shows the highest PCE ever reported in PSCs fabricated by a scalable process. To understand the origin of the high performance of the slot-die coated device, slot-die coated photoactive films and devices are systematically investigated. These results indicate that the good performance of the slot-die PSCs can be due to a favorable moleculestructure and film-morphology change by introducing 1,8-diiodooctane and heat treatment, which can lead to improved charge transport with reduced carrier recombination. The optimized condition is then used for the fabrication of large-area modules and also for roll-to-roll fabrication. The slot-die coated module with 30 cm 2 active-area and roll-to-roll produced flexible PSC has shown 8.6% and 9.6%, respectively. These efficiencies are the highest in each category and demonstrate the strong potential of the slot-die coated ternary system for commercial applications. Photovoltaic DevicesThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.Over the past few decades, solution-processed bulk-heterojunction (BHJ) polymer solar cells (PSCs) have continued to demonstrate their potential as a high-ef...