Browsing by Author "Wei, Kung-Hwa"

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2-Alkyl-5-thienyl-Substituted Benzo[1,2-b:4,5-b ']dithiophene-Based Donor Molecules for Solution-Processed Organic Solar Cells
(2013-10-09)
Patra, Dhananjaya
;
Huang, Tzu-Yen
;
Chiang, Chao-Cheng
;
Maturana, Ramon Orlando Valencia
;
Pao, Chun-Wei
In this study, we have strategically designed and convergently synthesized two novel, symmetrical, and linear A-D-A-type pi-conjugated donor molecules (TBDTCNR, TBDTCN), each containing a planar electron-rich 2-octylthiene-5-yl-substituted benzodithiophene (TBDT) unit as the core, flanked by octylthiophene units and end-capped with electron-deficient cyanoacetate (CNR) or dicyanovinyl (CN) units. We thoroughly characterized both of these materials and investigated the effects of the end groups (CNR, CN) on their optical, electrochemical, morphological, and photovoltaic properties. We then fabricated solution-processed bulk heterojunction organic solar cells incorporating TBDTCNR and TBDTCN. Among our tested devices, the one containing TBDTCNR and [6,6]-phenyl-C-61-butyric acid methyl ester in a 1:0.40 ratio (w/w) exhibited the highest power conversion efficiency (5.42%) with a short-circuit current density (J(sc)) of 9.08 mA cm(-2), an open circuit voltage (V-oc) of 0.90 V, and an impressive fill factor (FF) of 0.66 under AM 1.5G irradiation (100 mW cm(-2)). The FFs of these solution-processed small-molecule organic solar cells (SMOSCs) are outstanding when compared with those recently reported for benzodithiophene (BDT)-based SMOSCs, because of the high crystallinity and excellent stacking properties of the TBDT-based compounds.
A block copolymer enhances the efficiency of small-molecule bulk-heterojunction photovoltaics
(2016-01-01)
Chen, Hsiu-Cheng
;
Su, Yu-Wei
;
Wei, Kung-Hwa
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Block copolymers can self-assemble into ordered structures having feature dimensions on the order of 10 to 100 nm; we took advantage of the different polarities of the blocks of a low-molecular-weight diblock copolymer polystyrene-b-poly(ethylene oxide) (PS-b-PEO) that interact differentially with small molecules and fullerenes to tune the extent of phase separation in solution-processed small-molecule bulk-heterojunction (SMBHJ) solar cells. We incorporated small amounts of nanostructured PS-b-PEO to solar cells\' active layers featuring 7,7\'-{4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b\']dithiophene-2,6-diyl} bis{6-fluoro-4-(5\'-hexyl-[2,2\'-bithiophen]-5-yl) benzo[c] [1,2,5]thiadiazole} (p-DTS(FBTTh2)(2)) and [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) for optimizing the morphology and thus enhancing the devices\' power conversion efficiency. For understanding the effect of PS-b-PEO on the devices\' performances, we used synchrotron grazing-incidence wide-angle X-ray scattering, atomic force microscopy and transmission electron microscopy to probe and to decipher the morphologies of the resulting SMBHJ thin films. Without undergoing any annealing process, a device with an active layer of p-DTS(FBTTh2)(2): PC71BM (1.5 : 1, w/w) that incorporated 0.5 wt% of PS-b-PEO and was processed with a 1,8-diiodooctane solvent additive displayed a power conversion efficiency (PCE) of 7.3%, a relative increase of 2.5 times as compared to the PCE of 2.1% for the control device featuring only p-DTS(FBTTh2)(2) and PC71BM. Thus, incorporating this nanostructured block copolymer in the active layer allowed effective tuning of the small molecule active layer morphology and resulted in enhanced device efficiency.
A block copolymer enhances the efficiency of small-molecule bulk-heterojunction photovoltaics
(2016)
Chen, Hsiu-Cheng
;
Su, Yu-Wei
;
Wei, Kung-Hwa
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Block copolymers can self-assemble into ordered structures having feature dimensions on the order of 10 to 100 nm; we took advantage of the different polarities of the blocks of a low-molecular-weight diblock copolymer polystyrene-b-poly(ethylene oxide) (PS-b-PEO) that interact differentially with small molecules and fullerenes to tune the extent of phase separation in solution-processed small-molecule bulk-heterojunction (SMBHJ) solar cells. We incorporated small amounts of nanostructured PS-b-PEO to solar cells\' active layers featuring 7,7\'-{4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b\']dithiophene-2,6-diyl} bis{6-fluoro-4-(5\'-hexyl-[2,2\'-bithiophen]-5-yl) benzo[c] [1,2,5]thiadiazole} (p-DTS(FBTTh2)(2)) and [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) for optimizing the morphology and thus enhancing the devices\' power conversion efficiency. For understanding the effect of PS-b-PEO on the devices\' performances, we used synchrotron grazing-incidence wide-angle X-ray scattering, atomic force microscopy and transmission electron microscopy to probe and to decipher the morphologies of the resulting SMBHJ thin films. Without undergoing any annealing process, a device with an active layer of p-DTS(FBTTh2)(2): PC71BM (1.5 : 1, w/w) that incorporated 0.5 wt% of PS-b-PEO and was processed with a 1,8-diiodooctane solvent additive displayed a power conversion efficiency (PCE) of 7.3%, a relative increase of 2.5 times as compared to the PCE of 2.1% for the control device featuring only p-DTS(FBTTh2)(2) and PC71BM. Thus, incorporating this nanostructured block copolymer in the active layer allowed effective tuning of the small molecule active layer morphology and resulted in enhanced device efficiency.
A crystalline low-bandgap polymer comprising dithienosilole and thieno[3,4-c] pyrrole-4,6-dione units for bulk heterojunction solar cells
(2011-06-08)
Yuan, Mao-Chuan
;
Chou, Yi-Jen
;
Chen, Chia-Min
;
Hsu, Chang-Lung
;
Wei, Kung-Hwa
We have used Stille coupling polymerization to synthesize a new low-bandgap conjugated polymer, PDTSTPD, that consists of an electron-rich dithieno[3,2-b:2',3'-d]-silole (DTS) unit and an electron-deficient thieno[3,4-c]pyrrole-4,6-dione (TPD) moiety. The polymer exhibited an excellent thermal stability, crystalline characteristics, a broad spectral absorption, and a deep highest occupied molecular orbital (HOMO) energy level, resulting from combination of the rigid TPD and the coplanar DTS units in the polymer backbone. Moreover, the presence of the silicon atoms along the polymer chain ensured PDTSTPD having strong interchain stacking and good hole mobility. An optimal device incorporating the PDTSTPD:PC(71)BM blend at a weight ratio of 1:1 provided a power conversion efficiency of 3.42%. (c) 2011 Elsevier Ltd. All rights reserved.
A dual-functional additive improves the performance of molecular bulk heterojunction photovoltaic cells
(2014)
Farahat, Mahmoud E.
;
Wei, Hung-Yu
;
Ibrahem, Mohammed Aziz
;
Boopathi, Karunakara Moorthy
;
Wei, Kung-Hwa
In this paper we report a simple and effective approach towards improving the performance of molecular bulk heterojunction (BHJ) photovoltaics through incorporation of a new, nonvolatile processing additive; (3-chloropropyl) trimethoxysilane (CP3MS). A small amount of the additive CP3MS combined with post-annealing treatment significantly enhanced the power conversion efficiency (PCE) of dialkylated diketopyrrolopyrrole chromophore (SMDPPEH)-based molecular BHJ solar cells. The PCE increased from 2.75% for a device prepared without the additive or annealing to 4.55% for a device containing 0.1% CP3MS that had been subjected to post-annealing treatment at 100 degrees C for 10 min. CP3MS performed an interesting dual function when incorporated as an additive in molecular BHJ devices. The first was that it controlled the morphology: the addition of 0.1% CP3MS to the SMDPPEH: PC61BM blend was sufficient to improve the film's crystallinity and morphology. The second function was the spontaneous migration of the CP3MS molecules from the bulk to the interface between the active layer and the Al cathode, forming an ultrathin interlayer that acted as a buffer layer suppressing charge recombination and enhancing charge transport at the interface. Analyses using atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, together with examinations of device performance, confirmed the dual-functional nature of CP3MS as an additive. CP3MS also showed its promising ability to enhance the performance of different blend systems. The performance of benzodithiophene (BDT)-based molecular solar cells enhanced from 3.05% without additive to 3.8% with the incorporation of 0.1% CP3MS.
A nanostructured micellar diblock copolymer layer affects the memory characteristics and packing of pentacene molecules in non-volatile organic field-effect transistor memory devices
(2013)
Chen, Chia-Min
;
Liu, Chih-Ming
;
Tsai, Ming-Chang
;
Chen, Hsiu-Cheng
;
Wei, Kung-Hwa
Organic field-effect transistor (OFET) memory devices incorporating the copolymer polystyrene-block-poly(4-vinylpyridine) (PS56k-b-P4VP(8k)) layer, which features a thickness-dependent micellar nanostructure (P4VP-core, PS-shell), as a charge trapping layer can exhibit tunable memory windows for p-channel applications. For instance, the memory window increased substantially from 7.8 V for the device incorporating a 60 nm thick PS56k-b-P4VP(8k) layer to 21 V for the device incorporating a 27 nm thick layer, an increase of more than 2.5 times. Using simultaneous synchrotron grazing-incidence small-angle X-ray scattering and wide-angle X-ray scattering to probe the nanostructured micellar PS56k-b-P4VP(8k) layer and the pentacene layer positioned directly on the top of the copolymer layers, respectively, we were able to elucidate the structural characteristics of the bilayer and to correlate their effects with the memory performances of devices with similar architectures. For the PS56k-b-P4VP(8k) layers, we found that the inter-micelle distance and their lateral arrangements depended on the layer thickness: the thickness of the PS shells in the lateral direction decreased upon increasing the layer thickness, as did the memory window for the OFET device that incorporated the PS56k-b-P4VP(8k) layers, showing a strong dependence of the threshold voltage shifts (i.e., memory window) on the distance between the micelles. Additionally, for the molecular packing of the pentacene layer positioned on the copolymer layer, we found that the PS56k-b-P4VP(8k) layers affected not only the orientation of the pentacene molecules but also their grain sizes, thereby affecting the hole mobility of the memory devices. These results suggest that tuning the micellar nanostructure of the block copolymer thin film that was used as a trapping layer can be a simple and effective way for optimizing the memory window and affecting the hole mobility of OFET memory devices.
A new redox phloroglucinol additive incorporated gel polymer electrolyte for flexible symmetrical solid-state supercapacitors
(2019-06-01)
Phuoc-Anh Le
;
Van-Truong Nguyen
;
Yen, Po-Jen
;
Tseng, Tseung-Yuen
;
Wei, Kung-Hwa
We reported a new and environmentally friendly phloroglucinol additive incorporated polyvinyl alcohol-LiClO4 gel polymer electrolyte for flexible symmetrical solid-state supercapacitors. The incorporation of 10 wt% phloroglucinol into PVA-LiClO4 gel polymer electrolytes results in much higher specific capacitance (114 F g(-1)) than that without phloroglucinol (60 F g(-1)), an increase of 90%, because of the redox reaction of phloroglucinol in the system. We used the PVA-LiClO4 with 10 wt% phloroglucinol as a gel polymer electrolyte in combination with nitrogen-doped graphene nanosheet-based electrodes as the anode and cathode to fabricate a symmetrical solid-state supercapacitor. The fabricated supercapacitor involving the phloroglucinol redox additive has an energy density of 2.3 W h kg(-1) at a power density of 150 W kg(-1), which is higher than the one without a redox additive (1.9 W h kg(-1) at a power density of 150 W kg(-1)). Moreover, the supercapacitor involving the redox additive has good stability; its capacitance remains at up to similar to 94% after 5000 charge/discharge cycles.
A Perspective on Recent Advances in 2D Stanene Nanosheets
(1970-01-01)
Sahoo, Sumanta Kumar
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Wei, Kung-Hwa
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交大名義發表
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National Chiao Tung University
Advancements in 2D nanomaterials have been impacting a wide range of technology-driven applications. Here, the authors highlight stanene, a material that comprises a monolayer of elemental tin atoms, as a new addition to the monoelemental 2D family. Recent successes in the experimental realization of stanene in supported heterostructures and in free-standing form have expanded interest in exploring and unlocking its potential applications, as predicted from advanced theoretical calculations. Stanene exhibits several remarkable features, including a large spin-orbit gap (allowing room-temperature electronics based on the quantum spin Hall effect), topological superconductivity, quantum anomalous Hall behavior, giant magnetoresistance, and efficient thermoelectricity. Research into stanene and stanene-based 2D materials, both experimentally and theoretically, is suggesting immense potential for future quantum-based electronics systems. Here, the fundamental features of stanene, progress in its synthesis, and future perspectives are discussed.
A Tetraperylene Diimides Based 3D Nonfullerene Acceptor for Efficient Organic Photovoltaics
(2015-04)
Liu, Shi-Yong
;
Wu, Chen-Hao
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Li, Chang-Zhi
;
Liu, Sheng-Qiang
;
Wei, Kung-Hwa
A Tetraperylene Diimides Based 3D Nonfullerene Acceptor for Efficient Organic Photovoltaics
(2015-04-01)
Liu, Shi-Yong
;
Wu, Chen-Hao
;
Li, Chang-Zhi
;
Liu, Sheng-Qiang
;
Wei, Kung-Hwa
A Thieno[3,4-c]pyrrole-4,6-dione-Based Donor-Acceptor Polymer Exhibiting High Crystallinity for Photovoltaic Applications
(2010-09-14)
Yuan, Mao-Chuan
;
Chiu, Mao-Yuan
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Liu, Shih-Pin
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Chen, Chia-Min
;
Wei, Kung-Hwa
Activating basal-plane catalytic activity of two-dimensional MoS2 monolayer with remote hydrogen plasma
(2016-12)
Cheng, Chia-Chin
;
Lu, Ang-Yu
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Tseng, Chien-Chih
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Yang, Xiulin
;
Hedhili, Mohamed Nejib
Two-dimensional layered transition metal dichalcogenide (TMD) materials such as Molybdenum disufide (MoS2) have been recognized as one of the low-cost and efficient electrocatalysts for hydrogen evolution reaction (HER). The crystal edges that account for a small percentage of the surface area, rather than the basal planes, of MoS2 monolayer have been confirmed as their active catalytic sites. As a result, extensive efforts have been developing in activating the basal planes of MoS2 for enhancing their HER activity. Here, we report a simple and efficient approach using a remote hydrogen-plasma process to creating S-vacancies on the basal plane of monolayer crystalline MoS2; this process can generate high density of S-vacancies while mainly maintaining the morphology and structure of MoS2 monolayer. The density of S-vacancies (defects) on MoS2 monolayers resulted from the remote hydrogen-plasma process can be tuned and play a critical role in HER, as evidenced in the results of our spectroscopic and electrical measurements. The H-2-plasma treated MoS2 also provides an excellent platform for systematic and fundamental study of defect-property relationships in TMDs, which provides insights for future applications including electrical, optical and magnetic devices. (C) 2016 Elsevier Ltd. All rights reserved.
An optical programming/electrical erasing memory device: Organic thin film transistors incorporating core/shell CdSe@ZnSe quantum dots and poly(3-hexylthiophene)
(2009-08-01)
Chiu, Mao-Yuan
;
Chen, Chen-Chia
;
Sheu, Jeng-Tzong
;
Wei, Kung-Hwa
;
材料科學與工程學系
An optical programming/electrical erasing memory device was fabricated by adopting organic thin film transistors incorporating core/shell CdSe@ZnSe quantum dots (QDs) and poly(3-hexylthiophene) (P3HT) as active layers. After illumination, the presence of quantum well-structured core/shell CdSe@ZnSe QDs within the P3HT film enhanced the maximum ON/OFF ratio substantially to 2700; this value was maintained for 8000 s without noticeable decay. The ON state current could be erased effectively when using a single pulse of the gate voltage (- 10 V). This fabrication approach opens up the possibility of improving the memory performance of polymeric materials prepared at low cost using simple processes, (C) 2009 Elsevier B.V. All rights reserved.
An Organic Hole Transport Layer Enhances the Performance of Colloidal PbSe Quantum Dot Photovoltaic Devices
(2010-10-22)
Kuo, Chih-Yin
;
Su, Ming-Shin
;
Hsu, Yu-Chien
;
Lin, Hui-Ni
;
Wei, Kung-Hwa
A thin poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) hole transport layer enhances the AM1.5 power conversion efficiency of a PbSe quantum dot (QD)-containing photovoltaic device to 2.4%, from 1.5% for a standard PbSe QD device, a relative increase of 60%. Synchrotron X-ray reflectivity measurements reveal that the roughness of the interfaces between the various layers decreases dramatically in the presence of the PEDOT: PSS layer. In addition, the device life time under continuous simulated AM1.5 irradiation (100 mW cm(-2)), measured in terms of the time required to reach 80% of the normalized efficiency, for the PbSe QD device incorporating the PEDOT:PSS hole transport layer is six times longer than that of the standard PbSe QD device.
An Organic Hole Transport Layer Enhances the Performance of Colloidal PbSe Quantum Dot Photovoltaic Devices
(2010-10-22)
Kuo, Chih-Yin
;
Su, Ming-Shin
;
Hsu, Yu-Chien
;
Lin, Hui-Ni
;
Wei, Kung-Hwa
A thin poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) hole transport layer enhances the AM1.5 power conversion efficiency of a PbSe quantum dot (QD)-containing photovoltaic device to 2.4%, from 1.5% for a standard PbSe QD device, a relative increase of 60%. Synchrotron X-ray reflectivity measurements reveal that the roughness of the interfaces between the various layers decreases dramatically in the presence of the PEDOT: PSS layer. In addition, the device life time under continuous simulated AM1.5 irradiation (100 mW cm(-2)), measured in terms of the time required to reach 80% of the normalized efficiency, for the PbSe QD device incorporating the PEDOT:PSS hole transport layer is six times longer than that of the standard PbSe QD device.
An universal electron transport layer involving hydrogen plasma-treated tungsten disulfide nanosheets doped zinc oxide layers for polymer donors with fullerene or small molecule acceptor photovoltaics
(2019-09-01)
Huang, Yi-Jiun
;
Yen, Po-Jen
;
Wang, Hao-Cheng
;
Chen, Hsiu-Cheng
;
Wei, Kung-Hwa
A new universal electron transport layer that involves doping hydrogen-plasma-treated tungsten disulfide (WS2) nanosheets into ZnO for polymer/fullerene or small molecule organic photovoltaics (OPVs) was prepared. A hydrogen plasma treatment was used to alter the structures of WS2 nanosheets such that the W6+ content was converted into W4+; then ZnO:WS2 nanosheets composites were prepared to form electron transport layers (ETLs). The energy band of the ZnO:WS2 films could be tuned from 5.15 to 4.60 eV by varying the concentration of the WS2 nanosheets up to 0.5 wt%. It was found that ZnO:WS2 ETLs exhibited superior charge transport properties than those of the pristine ZnO layer because of the structure changes, as determined from the X-ray scattering characterizations. OPVs incorporating active layers of PTB7-TH/PC71BM and PTB7-TH/IDIC blends exhibited their power conversion efficiencies of 10.3% and 6.7%, respectively, with the incorporation of 0.3 wt% of the WS2 nanosheets, up from 8.9% to 5.4% for the corresponding devices featuring pristine ZnO-relative increases of 16% and 24%, respectively. This study demonstrates the effectiveness of hydrogen plasma treatment for altering the surface structures of two-dimensional transition-metal-dichalcogenide nanosheets, and paves a way for the composite electron transport layers for use in organic photovoltaics.
Annealing treatment improves the morphology and performance of photovoltaic devices prepared from thieno[3,4-c]pyrrole-4,6-dione-based donor/acceptor conjugated polymers and CdSe nanostructures
(2011-06-01)
Kuo, Chih-Yin
;
Su, Ming-Shi
;
Chen, Guan-Yu
;
Ku, Ching-Shun
;
Lee, Hsin-Yi
We have prepared photovoltaic devices based on blend films of CdSe tetrapods and the donor/acceptor conjugated polymer PDTTTPD, which comprises 2,5-di(thiophen-2-yl) thieno[3,2-b]thiophene and thieno[3,4-c]pyrrole-4,6-dione units. The AM1.5 power conversion efficiency (PCE) of a photovoltaic device containing a PDTTTPD/CdSe tetrapod blend (1:9, w/w) that had experienced thermal annealing (130 degrees C, 20 min) was three times greater than that of the corresponding device incorporating the as-prepared PDTTTPD/CdSe tetrapod blend (2.9% vs. 1.0%). Synchrotron X-ray reflectivity revealed that annealing (i.e., removal of pyridine ligands from the surfaces of the CdSe tetrapods) caused the thickness of the PDTTTPD/CdSe tetrapod blend film to decrease (and its average density to increase) relative to that of the as-prepared blend film. Transmission electron microscopy and atomic force microscopy revealed that thermal annealing enhanced the degree of aggregation of the CdSe tetrapods and induced denser morphologies, leading to substantially increased charge transport, which enhanced the PCE of the device.
Au@Cu2O core@shell nanocrystals as dual-functional catalysts for sustainable environmental applications
(2019-03-01)
Kuo, Ming-Yu
;
Hsiao, Chih-Feng
;
Chiu, Yi-Hsuan
;
Lai, Ting-Hsuan
;
Fang, Mei-Jing
This work reports the synthesis of Au@Cu2O core@shell nanocrystals with controllable shell thicknesses and demonstrates their use as the dual-functional catalyst that can continuously operate under illumination and darkness conditions for efficient E. con inactivation. On account of the peroxidase mimics of the Au core and Fenton reactivity of the Cu2O shell, the Au@Cu2O nanocrystals exhibit intrinsic peroxidase-like property with the reaction kinetics in accordance with the typical Michaelis-Menten mechanism. On the other hand, time resolved photoluminescence spectra suggest the prevalence of pronounced charge separation for Au@Cu2O nanocrystals, an important advantage that is favourable for photocatalysis. By combining the photocatalytic capability with the peroxidase mimics features, Au@Cu2O nanocrystals can perform practical photocatalytic decomposition of E. coil under visible light illumination but still show vital activity towards E. coil inactivation after light illumination was turned off. The current study delivers a new catalyst configuration by exploiting the multiple functionalities of nanosized Au and Cu2O for advanced environmental and energy conversion applications.
Benzooxadiazole-based donor/acceptor copolymers imparting bulk-heterojunction solar cells with high open-circuit voltages
(2013-01-08)
Jiang, Jian-Ming
;
Yang, Po-An
;
Lan, Shang-Che
;
Yu, Chia-Ming
;
Wei, Kung-Hwa
In this study we used Suzuki cross-coupling to synthesize three new donor/acceptor copolymers-PFTBO, PAF1130, and PCTBO-featuring soluble alkoxy-modified 2,1,3-benzooxadiazole (BO) moieties as acceptor units and electron-rich building blocks-dialkyl fluorene (F), alkylidene fluorene (AF), and carbazole (C), respectively-as donor units. These polymers, which we characterized using gel permeation chromatography, thermogravimetric analysis, NMR spectroscopy, UV-Vis absorption spectroscopy, and electrochemical cyclic voltammetry, exhibited good solubility, low-lying energy levels for their highest occupied molecular orbitals, excellent thermal stability, and air stability. Using these polymers, we fabricated bulk-heterojunction solar cell devices having the structure indium tin oxide/poly(3,4-ethylenedioxythiophene):polystyrenesulfonate/polymer:[6,6]-phenyl-C-61-butyric acid methyl ester (PC61BM) (1:1, w/w)/Ca/Al. Under AM 1.5G illumination (100 mW cm(-2)), the solar cell incorporating PFTBO exhibited a high value of V-OC of 1.04 V and that based on PCTBO provided a power conversion efficiency of 4.1% without the need for any post treatment. (C) 2012 Elsevier Ltd. All rights reserved.
Block Copolymer-Tuned Fullerene Electron Transport Layer Enhances the Efficiency of Perovskite Photovoltaics
(2016-09-21)
Lin, Hsi-Kuei
;
Su, Yu-Wei
;
Chen, Hsiu-Cheng
;
Huang, Yi-Jiun
;
Wei, Kung-Hwa
In this study, we enhanced the power conversion efficiency (PCE) of perovskite solar cells by employing an electron transfer layer (ETL) comprising [6,6]phenyl-C-61-butyric acid methyl ester (PC61BM) and, to optimize its morphology, a small amount of the block copolymer polystyreneb-poly(ethylene oxide) (PS-b-PEO), positioned on the perovskite active layer. When incorporating 0.373 wt, % PS-b-PEO into PC61BM, the PCE of the perovskite photovoltaic device increased from- 9.4% to 13.4%, a relative increase of 43%, because of a large enhancement in the fill factor of the device. To\' decipher the intricate morphology of the ETL, we used synchrdtron grazing-incidence small-angle X-ray scattering for determining the PC61BM cluster site, atomic force microscopy and scanning electron microscopy for probing the-surface, and transmission electron microscopy for observing the aggregation of PC61BM in the ETL. We found that the interaction between PS-b-PEO and PC61BM resulted in smaller PC61BM dusters that further aggregated into dendritic structures in some domains, a result of the similar polarities of the PS block and PC61BM; this behavior could \'be used to tune the morphology of the ETL. The optimal PS-b-PEO-mediated PC61BM cluster size in the ETT, was 17 nm, a large reduction from 59 nin for the pristine PC61BM layer. This approach ofincorporating a small amount of nanostructured block copolymer into a fullerene allowed us to effectively tune the morphology of the ETL on the perovskite active layer and resulted in enhanced fill factors of the devices and thus their device efficiency.