Performance Improvement of Polymer Solar Cells by Surface-Energy

Subscriber access provided by TEXAS A&M INTL UNIV

Article

Performance improvement of polymer solar cells by surface- energy-induced dual plasmon resonance Mengnan Yao, Ping Shen, Yan Liu, Boyuan Chen, Wenbin Guo, Shengping Ruan, and Liang Shen ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b00297 • Publication Date (Web): 22 Feb 2016 Downloaded from http://pubs.acs.org on February 22, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Performance improvement of polymer solar cells by surfaceenergy-induced dual plasmon resonance Mengnan Yao a, Ping Shen a, Yan Liu b, Boyuan Chen a, Wenbin Guo a, Shengping Ruan a, Liang Shen a,* a

State Key Laboratory on Integrated Optoelectronics, College of Electronic Science

and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, People’s Republic of China. b

Key Laboratory of Bionic Engineering (Ministry of Education), Jilin University,

Changchun 130022, People’s Republic of China.

ABSTRACT The surface plasmon resonance (SPR) effect of metal nanoparticles (MNPs) is effectively applied on polymer solar cells (PSCs) to improve power conversion efficiency (PCE). However, universality of the reported results mainly focused on utilizing single type of MNPs to enhance light absorption only in specific narrow wavelength range. Herein, a surface-energy-induced dual MNPs plasmon resonance by thermally evaporating method was presented to achieve the absorption enhancement in wider range. The differences of surface energy between silver (Ag), gold (Au), and tungsten trioxide (WO3) compared by contact angle images enable Ag and Au prefer to respectively aggregate into isolated islands rather than films at the initial stage of the evaporation process, which was clearly demonstrated in the atom force microscopy (AFM) measurement. The sum of plasmon-enhanced wavelength

1

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 27

range induced by both Ag NPs (350-450 nm) and Au NPs (450-600 nm) almost cover the whole absorption spectra of active layer, which compatibly contribute a significant efficiency improvement from 4.57±0.16 % to 6.55±0.12 % compared to the one without MNPs. Besides, steady state photoluminescence (PL) measurements provide a strong evidence that the SPR induced by the Ag-Au NPs increase the intensity of light absorption. Finally, ultraviolet photoelectron spectroscopy (UPS) reveals that doping Au and Ag causes upper shift of both the work function and valence band of WO3, which is directly related to holes collection ability. We believe the surface-energy-induced dual plasmon resonance enhancement by simple thermally evaporating technique might pave the way toward higher-efficiency PSCs.

KEYWORDS:

surface

energy,

plasmon

resonance,

photoluminescence, buffer layer, polymer solar cells

*Corresponding Author

E-mail: [email protected]

2


metal

nanoparticles,

Page 3 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1. INTRODUCTION Solution-processed polymer solar cells (PSCs) are competing with traditional inorganic thin film solar cells owing to their unique properties such as light weight, low-cost, mechanical flexibility and large-area technology.1-5 To date, power conversion

efficiencies

(PCEs)

more

than

10%

have

been

realized

in

bulk-heterojunction (BHJ) PSCs, demonstrating a promising potential for future commercialization.6-10 However, the achievement of polymer with both high mobility and wide-spectrum absorption remains a challenge, which has severely limited further PCE improvement. The intrinsic disadvantages such as high exciton binding energy, large bandgap, short exciton diffusion length and low carrier mobility of polymer lead to a trade-off between photoactive layers thickness and photocurrent current. Severe charge recombination which decrease the fill factor (FF) of devices becomes more dominant as the thickness of photoactive layers increases.11-13 Therefore, the case how to achieve a light absorption enhancement without increasing the thickness of photoactive layer, triggers the emergence of new research highlights - light trapping methods(or light management).14-18 So far, various kinds of methods and structures were exploited to enhance light-trapping process in devices by optical strategies, such as microcavity,19-23 photonic crystal24-27 and plasmon resonance effect.28-34 Generally, the enhanced optical absorption based on the plasmonic effect can be obtained through the methods of (Ι) process of plasmon-enhanced scattering, (Π) propagation of surface plasmon polariton (SPP) modes, and (Ⅲ) excitation of localized surface plasmon (LSP) of metal nanoparticles (MNPs).35-37 Especially, LSP 3



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 27

are the oscillation of conduction electrons in finite-sized particle, while SPP are surface electromagnetic (EM) waves propagating along the metal surface. In the past, incorporating plasmonic NPs in the active layer to enhance the light absorption by surface plasmon resonances (SPR) are extensively studied in PSCs.38-41 Nevertheless, the addition of NPs in the active layer may give rise to exciton quenching enhancement. Therefore recently, MNPs were preferred to be placed into the buffer layer where the LSPR effect can extend into the active layer and reduce the device resistance simultaneously, which played a important role in longer-period light trapping and increased interaction time with light.42 Meanwhile, the back scattering of light induced by MNPs also caused an increase in the optical path length to contribute more photogeneration.43,

44

Yang et al.45 reported on the introduction of

11-Mercaptoundecanoic acid (MUA) stabilized Au NPs embedded into the copper phthalocyanine (CuPc) buffer layer in poly(3- hexyl-thiophene) (P3HT)/[6,6]-phenyl C61-butyric acid methyl ester (PCBM) bulk heterojunction (P3HT:PCBM) bulk heterojunction photovoltaic devices, which leads to an improvement over 25% enhancement of PCE. This was attributed partially to the improved ordering in the active layer with improved preferred orientation order of P3HT, and partially to the enhanced optical absorption by LSPR. Schwartzkopf and Santoro et al.46,

47

systematically present a fundamental study during the growth of nanoscale gold clusters onto inorganic surfaces using surface sensitive X-ray scattering methods, permitting a deeper understanding of the different growth regimes of Ag nanoparticles on ﬂat inorganic surfaces accompanied with the correlation of morphological 4


Page 5 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


parameters of Ag nanostructured thin ﬁlms with their surface enhanced Raman scattering (SERS) activity. Recently, they48 further demonstrated how optical reflectivity in the ultraviolet/visible range and plasmon resonance correlate with the morphology of the Au cluster layer. A maximum in anti-reflectivity was found for Au cluster layers around 1 nm film thickness, which might corroborate the findings of enhancement at this Au film thickness. In our previous investigation, Xu et al.43 and Yao et al.49 successfully applied simple thermally evaporating technique to deposit Ag, Au NPs respectively into the anode buffer layer of PSCs to improve PCE, respectively. However, a completely different phenomenon gives rise to our attention, that is, the device efficiency with Ag NPs sharply decreased with the increased diameter, but efficiency of Au NPs-based device increased stably until the formation of the Au film. Herein, we present a surface-energy-induced dual bimetallic nanoparticles (NPs) combining with Ag and Au into the WO3 anode buffer layer to enhance light absorption in wider range by SPR with thermally evaporating technique. Liu et al.50 reported Au nanodots and nanoparticles induced dual LSPR can compatibly improve the performance of PSCs, yielding a 15 % greater PCE than without. However, dual LSPR with different types of NPs have few reports. In this paper, the differences of the surface energy between Ag, Au, and WO3 lead to Ag and Au easily aggregated to form isolated islands rather than films, and the grain diameter can be easily modulated by the evaporating thickness. The compatible thickness of Ag and Au lead to a dramatically improved PCE from 4.57±0.16 % to 6.55 ±0.12 %. The ultraviolet photoelectron spectroscopy (UPS) results reveal the thicknesses of introduced Au and 5



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Ag have a strong impact on the work function and valence band of WO3, which directly affect the ability of transporting holes. We believe the thoughts can open a door to achieve multi-metals compatibly enhancing efficiency of PSCs.

2. EXPERIMENTAL SECTION The device have a structure of indium tin oxide (ITO)/PEI/ poly (3-hexylthiophene): Indene-C60 bisadduct (P3HT: ICBA)/WO3/Ag NPs/Au NPs/WO3/Ag and the preparation process is described as follows. The ITO coated glass substrates (a sheet resistance of 15Ω/sq) were precleaned by ultrasonic treatment in detergent, deionized water, acetone and isopropy alcohol. A 5nm-thick PEI (Aladdin Industrial Corporation) layer was spun coated on top of the ITO glass substrate, followed by low temperature annealing for 10 min. P3HT (Lumtec Corp, used as received) blending with ICBA (Lumtec Corp, used as received) in 1:1 weight ratio was dissolved in 1,2-Dichlorobenzene (DCB). The blend was stirred for 72 h in glovebox filled with argon. Then, the P3HT: ICBA active layer was prepared by spin coating at 1000 rmp for 30 s on top of PEI film, and solvent annealing with DCB for 8 h in glovebox. Finally, the samples were evaporated with 5 nm WO3, 2 nm Ag, x nm Au (x=0, 1, 2, 3), 5 nm WO3 and 100 nm Ag in sequence and a high vacuum (5×10-4 Pa). The deposition rate was about 0.2 nm s-1, which was monitored with a quartz-oscillating thickness monitor (ULVAC, CRTM-9000). The active area of the device was 0.064 cm2. Here, devices with different thicknesses of Ag and Au (monitor thickness when evaporation) are named as A (0 nm, 0 nm), B (2 nm, 0 nm), C (2 nm, 1 nm), D (2 nm, 2 nm), and E (2 nm, 3 nm), and devices only with different thicknesses of Ag are 6


Page 6 of 27

Page 7 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


named as A0 (0 nm), A1 (1 nm), A2 (2 nm), and A3 (3 nm). The J-V characteristic were measured with a computer-programmed Keithley 2601 source meter under AM1.5G solar illumination with an Oriel 300 W solar simulator intensity of 100 mW cm-2. The IPCE spectra were measured with Crowntech QTest Station 1000AD. The transmittance spectra were recorded using an ultraviolet/visible spectrometer (UV-1700, Shimadzu). The PL spectra were measured at room temperature and resolved by using a UV grating and a sensitive, calibrated liquid nitrogen cooled CCD camera. The sample-excited (a He-Cd CW) laser were operated at a wavelength of 470 nm with 50 mW power. Impedance spectroscopy, which measures the dielectric properties of a material and interface as function of frequency, was measured by an impedance analyzer (Wayne Kerr Electronics 6520B) with a bias of 1 V in the frequency range of 20 Hz to 2 MHz. AFM measurements in air were performed using a Solver Scanning Probe Microscope in contact mode. 3. EXPERIMENTAL AND SIMULATION RESULTS AND DISSCUSSION Figure 1a displays the device architecture based on Ag-Au NPs. The presence of Ag and Au NPs embedded in the WO3 buffer layer was evident from the AFM images recorded in the range of 1 × 1 µm2 by contact mode, which is shown in Figure 1b. The bigger bright spots are Ag islands and the smaller ones are Au islands, which are homogeneously dispersed on the surface of WO3. The diameter of Ag NPs are generally bigger than that of Au NPs, which has been respectively reported in our previous papers.43, 49 It means that the relatively uniform distribution of Ag-Au NPs can be achieved by simple thermal evaporation into WO3 anode buffer layer, and 7



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

these independent NPs meet the basic conditions to realize the SPR. It is noted that the universality exists in selecting transition metal oxides (MoO3, V2O5) as buffer layers, which have been further demonstrated in the research on interfacial engineering. 51-53 To demonstrate the cooperative effects of Ag-Au NPs on improving device performance by SPR in corresponding wavelength range, the IPCE spectra of devices A0-A3, B-E were measured and shown in Figure 2, respectively. It is observed from Figure 2a that the IPCE within the wavelength range of 350-500 nm increased significantly after incorporating Ag NPs, which indicates that Ag NPs induced plasmonic enhancement mainly work in short-wavelength range. Therefore in the process of fabricating devices B-E, the monitor thickness of evaporating Ag was fixed as 2 nm. As illustrated in Figure 2b, the best IPCE over 70 % is obtained from the device C. A remarkable enhancement appears in an extended wavelength of 450-600 nm compared to that of the device A, providing a direct evidence that Ag-Au NPs-induced SPR can widen light absorption spectra, which almost cover the whole intrinsic absorption range of active layer. To further determine device performance enhancement, the J-V characteristics of devices A-E were measured and shown in Figure 3, and the corresponding parameters were listed in detail in Table 1. It can be seen that the device A as a control sample exhibit a relatively low performance, including an open-circuit voltage (Voc) of 0.87±0.01 V, a short-circuit current (Jsc) of 7.91±0.14 mA cm-2, a fill factor (FF) of 64.6±0.2 %, and a calculated PCE of 4.57±0.16 %. Encouragingly, the Jsc was 8


Page 8 of 27

Page 9 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


dramatically increased to 11.01±0.12 mA cm-2, which led to an increased PCE up to 6.55±0.12 % in the device C. It is in a good accordance with IPCE variation tendency. It was noted that the value of Voc remained at 0.87±0.01 V, suggesting the unchanged built-in electrical field. It is noted that the FF of device C has some increase compared to device A, which can be attributed to the improved holes transport ability of WO3 layers after incorporating MNPs. It can be seen that device C has the smallest series resistance (Rs) and the biggest shunt resistance (Rsh), which result from decreasing holes aggregation and more balanced electron and hole transport. It is well known that the sum of absorption, reflection and transmittance is constant when the light goes through an interface. Therefore to further illustrate the mechanism of the Jsc improvement caused by absorption enhancement, the transmittance spectra of devices B-E without top Ag electrode were measured and shown in Figure 4. In this study, lower transmittance of the sample indicates that more incident photons can be trapped within the devices, which can potentially enhance the photon absorption efficiency of the active layer. It is clearly observed that all the devices incorporating Au NPs exhibit lower transmittance compared to the device B only with Ag NPs. Notably, the device C has a minimum valley around 500 nm in the transmittance spectra, which suggest that this combination can lead to the strongest reflection and absorption. It is in good consistent with the IPCE variation tendency. The contact angle of the ethylene glycol solvent was measured to further confirm surface energy difference between Ag and Au. As clearly compared in Figure 5a-c, the average contact angles of Ag, Au, and WO3 film are 66.31°, 60.02° and 38.39°, 9



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

respectively. The large gap between WO3 and Ag (Au) results in the case that metal easily aggregated to form isolated islands rather than films at the initial stage of the process of evaporation. Moreover, the subsequently evaporated Au NPs keep independent of Ag NPs instead of forming Ag-Au core–shell NPs due to several nanometer thickness,54,55 leading to compatibly enhancing light absorption at respective specific wavelength. To explore the optoelectronic properties of Ag-Au NPs by SPR effect, we directly performed steady state PL measurements. Because absorption of P3HT as electron donor was predominately contributed to the exciton generation in the active layer, thus the steady state PL spectra of ITO/PEI/P3HT, ITO/PEI/P3HT/Ag (2 nm), ITO/PEI/P3HT/Ag (2 nm)/Au (1 nm) devices are compared in Figure 6. It can be seen that devices with single Ag NPs and Ag-Au NPs show higher PL intensities than single P3HT film in the wavelength range from 650 nm to 750 nm when excited with 470 nm laser. Significantly, the PL intensity of devices with Ag-Au NPs is considerably higher than that of devices with single Ag NPs. The strong interparticle enhancement of electromagnetic field at Ag-Au NPs could effectively improve the exciton generation. Commonly, the steady state PL intensity is generally determined by two factors, the resonance frequency overlap between the absorption band gap of polymer and the nanostructure induced plasmonic effect. In previous reports using this method, 49, 56 it has been demonstrated that the resonance effect between the Au NPs and the absorption band of P3HT increased the degree of light absorption and the excitation rate by SPR effect. Therefore, the remarkable increase of fluorescence 10


Page 10 of 27

Page 11 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


intensity of Ag-Au NPs can be attributed to the stronger light absorption in P3HT than that of single metal NPs due to the excitation of the surface-energy-induced dual plasmon resonance. Buffer layers play an important role in PSCs as carrier transporting/blocking layers, so we continue to investigate the effect of doping NPs in buffer layer on interface electronic characteristic and try to find another origin of performance improvement with UPS measurement.57 Figure 7a reveals doping NPs into buffer layers cause the shift of Fermi energy level of WO3. After doping 2-5 nm thick Ag, the Fermi energy was driven up ~0.89 eV, suggesting vacuum level decreasing equivalently by ~0.89 eV. However, the energy difference between the valence band and zero binding energy show opposite views after inclusion of 2 nm or 5 nm Ag. For WO3/Ag (2 nm), the Φv1= 0.31 eV is much smaller than intrinsic value of Φv1= 1.58 eV of WO3. It is similar to P doping in WO3 because the Fermi level is closer to the valence band after doping 2 nm Ag. The decreased band energy is beneficial to photogenerated holes collection by the anode, which will lead to the performance improvement. Going on increasing the thickness of Ag to 5 nm, the Fermi level shifted up and much bigger Φv1= 3.08 eV was obtained. The similar N doping effect appears and the ability of conducting holes declines. The UPS results agree well with the J-V characteristics. The enhanced holes transporting ability of buffer layers after doping NPs will results the decreased contact resistance and enhanced photocurrent, so the impedance spectroscopy of devices were measured in the dark condition by Nyquist diagram. The complex impedance spectra of the devices B and C are shown in Figure 8. The 11



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

shapes of the impedance spectra are semicircles and beneficial to investigate the interface resistance in PSCs. It is noted that the diameter of the two semicircles for the two kinds of devices are different, they taper off with the increase of Au thickness. The diameter of the device B is much larger than that of device C. The decline of equivalent resistance means the introduction of Ag-Au NPs in WO3 buffer layer by thermally evaporating technique can effectively decrease the series resistance of PSCs, which is consistent with the enhanced photocurrent. 4. CONCLUSIONS In conclusion, surface-energy-induced high-performance inverted PSCs have been achieved using ingenious thermally evaporating Ag-Au NPs into WO3 buffer layer by plasmon resonance to enhance light absorption in wider range. The optimal device realizes efficiency as high as 6.55±0.12 %. The PL measurements of Ag-Au NPs reveal a prominent increase in fluorescence intensity of electron donor by the dual NPs plasmon resonance. Besides, UPS results provide a strong evidence that the work function and valence band of WO3 is sensitive to the thickness of Ag. The surface-energy-induced dual plasmon resonance enhancement by simple thermally evaporating technique will give a guideline for future investigation in high-efficiency PSCs.

ACKNOWLEDGMENT

The authors are grateful to National Natural Science Foundation of China (Grant nos. 61275035, 61370046, 51475200, 11574110), Key Technology Research and Development Program of Changchun (No.13KG66). 12


Page 12 of 27

Page 13 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


REFERENCES (1) Small, C. E.; Chen, S.; Subbiah, J.; Amb, C. M.; Tsang, S.-W.; Lai, T.-H.; Reynolds,

J.

R.;

So,

F.

High-Efficiency

Inverted

Dithienogermole

–

Thienopyrrolodione-Based Polymer Solar Cells. Nat. Photonics 2011, 6, 115-120. (2) Su, Y.-W.; Lan, S.-C.; Wei, K.-H. Organic Photovoltaics. Mater. Today 2012, 15, 554-562. (3) Earmme, T.; Hwang, Y. J.; Subramaniyan, S.; Jenekhe, S. A. All-Polymer Bulk Heterojuction Solar Cells with 4.8% Efficiency Achieved by Solution Processing from a Co-Solvent. Adv. Mater. 2014, 26, 6080-6085. (4) Intemann, J. J.; Yao, K.; Li, Y.-X.; Yip, H.-L.; Xu, Y.-X.; Liang, P.-W.; Chueh, C.-C.; Ding, F.-Z.; Yang, X.; Li, X.; Chen, Y.; Jen, A. K. Y. Highly Efficient Inverted Organic

Solar

Cells

through

Material

and

Interfacial

Engineering

of

Indacenodithieno[3,2-b]thiophene-Based Polymers and Devices. Adv. Funct. Mater. 2014, 24, 1465-1473. (5) Li, N.; Baran, D.; Spyropoulos, G. D.; Zhang, H.; Berny, S.; Turbiez, M.; Ameri, T.; Krebs, F. C.; Brabec, C. J. Environmentally Printing Efficient Organic Tandem Solar Cells with High Fill Factors: A Guideline Towards 20% Power Conversion Efficiency. Adv. Energy Mater. 2014, 4, 1-7. (6) Chen, C. C.; Chang, W. H.; Yoshimura, K.; Ohya, K.; You, J.; Gao, J.; Hong, Z.; Yang, Y. An Efficient Triple-Junction Polymer Solar Cell Having a Power Conversion Efficiency Exceeding 11%. Adv. Mater. 2014, 26, 5670-5677. (7) Vohra, V.; Kawashima, K.; Kakara, T.; Koganezawa, T.; Osaka, I.; Takimiya, K.; 13



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Murata, H. Efficient Inverted Polymer Solar Cells Employing Favourable Molecular Orientation. Nat. Photonics 2015, 9, 403-408. (8) Chen, J. D.; Cui, C.; Li, Y. Q.; Zhou, L.; Ou, Q. D.; Li, C.; Li, Y.; Tang, J. X. Single-Junction Polymer Solar Cells Exceeding 10% Power Conversion Efficiency. Adv. Mater. 2015, 27, 1035-1041. (9) Nian, L.; Zhang, W.; Zhu, N.; Liu, L.; Xie, Z.; Wu, H.; Wurthner, F.; Ma, Y. Photoconductive Cathode Interlayer for Highly Efficient Inverted Polymer Solar Cells. J. Am. Chem. Soc. 2015, 137, 6995-6998. (10) Kang, H.; Jung, S.; Jeong, S.; Kim, G.; Lee, K. Polymer-Metal Hybrid Transparent Electrodes for Flexible Electronics. Nat. Commun. 2015, 6, 6503-6510. (11) Huo, L.; Liu, T.; Sun, X.; Cai, Y.; Heeger, A. J.; Sun, Y. Single-Junction Organic Solar Cells Based on a Novel Wide-Bandgap Polymer with Efficiency of 9.7%. Adv. Mater. 2015, 27, 2938-2944. (12) Li, H.; Cao, J.; Zhou, Q.; Ding, L.; Wang, J. High-Performance Inverted PThTPTI: PC71BM Solar Cells. Nano Energy 2015, 15, 125-134. (13) Jia, X.; Shen, L.; Yao, M.; Liu, Y.; Yu, W.; Guo, W.; Ruan, S. Highly Efficient Low-Bandgap Polymer Solar Cells with Solution-Processed and Annealing-Free Phosphomolybdic Acid as Hole-Transport Layers. ACS Appl. Mater. Interfaces 2015, 7, 5367-5372. (14) Park, H. J.; Xu, T.; Lee, J. Y.; Ledbetter, A.; Guo, L. J. Photonic Color Filters Integrated with Organic Solar Cells for Energy Harvesting. ACS Nano 2011, 5, 7055-7060. 14


Page 14 of 27

Page 15 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(15) Ran, N. A.; Love, J. A.; Takacs, C. J.; Sadhanala, A.; Beavers, J. K.; Collins, S. D.; Huang, Y.; Wang, M.; Friend, R. H.; Bazan, G. C.; Nguyen, T. Q. Harvesting the Full Potential of Photons with Organic Solar Cells. Adv Mater. 2015, 4, 1-7. (16) Chen, P.-Y.; Dang, X.; Klug, M. T.; Qi, J.; Courchesne, N.-M. D.; Burpo, F. J.; Fang, N.; Hammond, P. T.; Belcher, A. M. Based Template for Dye-Sensitized Solar Cells with Improved Electron Transport and Light Harvesting. ACS Nano 2013, 7, 6563-6574. (17) Jeong, S.; Cho, C.; Kang, H.; Kim, K.-H.; Yuk, Y.; Park, J. Y.; Kim, B. J.; Lee, J.-Y. Nanoimprinting-Induced Nanomorphological Transition in Polymer Solar Cells: Enhanced Electrical and Optical Performance. ACS Nano 2015, 9, 2773-2782. (18) Yusoff, A. R. B. M; Lee, S. J.; Kim, H. P.; Shneider, F. K.; da Silva, W. J.; Jang, J. 8.91% Power Conversion Efficiency for Polymer Tandem Solar Cells. Adv. Funct. Mater. 2014, 24, 2240-2247. (19) Lin, H. W.; Chiu, S. W.; Lin, L. Y.; Hung, Z. Y.; Chen, Y. H.; Lin, F.; Wong, K. T. Device Engineering for Highly Efficient Top-Illuminated Organic Solar Cells with Microcavity Structures. Adv. Mater. 2012, 24, 2269-2272. (20) Li, J.; Xu, C.; Nan, H.; Jiang, M.; Gao, G.; Lin, Y.; Dai, J.; Zhu, G.; Ni, Z.; Wang, S.; Li, Y. Graphene Surface Plasmon Induced Optical Field Confinement and Lasing Enhancement in ZnO Whispering-Gallery Microcavity. ACS Appl. Mater. Interfaces 2014, 6, 10469-10475. (21) Yu, W.; Shen, L.; Meng, F.; Long, Y.; Ruan, S.; Chen, W. Effects of the Optical Microcavity on the Performance of ITO-Free Polymer Solar Cells with WO3/Ag/WO3 15



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Transparent Electrode. Sol. Energy Mater. Sol. Cells 2012, 100, 226-230. (22) Chen, Y.; Shen, L.; Yu, W.; Long, Y.; Guo, W.; Chen, W.; Ruan, S. Highly Efficient ITO-Free Polymer Solar Cells Based on Metal Resonant Microcavity Using WO3/Au/WO3 as Transparent Electrodes. Org. Electron. 2014, 15, 1545-1551. (23) Lai, Y.-Y.; Lan, Y.-P.; Lu, T.-C., Strong light–matter interaction in ZnO microcavities. Light: Sci. Appl. 2013, 2, e76. (24) Yang, Z.; Gao, S.; Li, W.; Vlasko-Vlasov, V.; Welp, U.; Kwok, W. K.; Xu, T. Three-Dimensional Photonic Crystal Fluorinated Tin Oxide (FTO) Electrodes: Synthesis and Optical and Electrical Properties. ACS Appl. Mater. Interfaces 2011, 3, 1101-1108. (25) Yu, W.; Jia, X.; Long, Y.; Shen, L.; Liu, Y.; Guo, W.; Ruan, S. Highly Efficient Semitransparent Polymer Solar Cells with Color Rendering Index Approaching 100 Using One-Dimensional Photonic Crystal. ACS Appl. Mater. Interfaces 2015, 7, 9920-9928. (26) Yu, W.; Shen, L.; Long, Y.; Shen, P.; Guo, W.; Chen, W.; Ruan, S. Highly Efficient and High Transmittance Semitransparent Polymer Solar Cells with One-Dimensional Photonic Crystals as Distributed Bragg Reflectors. Org. Electron. 2014, 15, 470-477. (27) Shi, X.; Shi, L.; Li, M.; Hou, J.; Chen, L.; Ye, C.; Shen, W.; Jiang, L.; Song, Y. Efficient Luminescence of Long Persistent Phosphor Combined with Photonic Crystal. ACS Appl. Mater. Interfaces 2014, 6, 6317-6321. (28) Liu, X.; Wu B.; Zhang, Q.; Yip, J. N.; Yu, G.; Xiong, Q.; Mathews, N.; Sum, T. C. 16


Page 16 of 27

Page 17 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Elucidating the Localized Plasmonic Enhancement Effects from a Single Ag Nanowire in Organic Solar Cells. ACS Nano 2014, 8, 10101-10110. (29) Park, H. II.; Lee, S.; Lee, J. M.; Nam, S. A.; Jeon, T.; Han, S. W.; Kim, S. O. High

Performance

Organic

Photovoltaics

with

Plasmonic-Coupled

Metal

Nanoparticle Clusters. ACS Nano 2014, 8, 10305-10312. (30) Jung, K.; Song, H.-J.; Lee, G.; Ko, Y.; Ahn, K.; Choi, H.; Kim, J. Y.; Ha, K.; Song, J.; Lee, J.-k.; Lee, C.; Choi, M. Plasmonic Organic Solar Cells Employing Nanobump Assembly via Aerosol-Derived Nanoparticles. ACS Nano 2014, 8, 2590-2561. (31) Sandén, S.; Akitsu, K.; Törngren, B.; Ylinen, A.; Smått, J.-H.; Kubo, T.; Matsumura, M.; Otani, N.; Segawa, H.; Österbacka, R. Plasmon-Enhanced Polymer-Sensitized Solar Cells. J. Phys. Chem. C 2015, 119, 5570-5576. (32) Park, B; Yun, S. H.; Cho, C. Y.; Kim, Y. C.; Shin, J. C.; Jeon, H. G.; Huh, Y. H.; Hwang, I.; Baik, K. Y.; Lee, Y. I.; Uhm, H. S.; Cho, G. S.; Choi, E. H., Surface plasmon excitation in semitransparent inverted polymer photovoltaic devices and their applications as label-free optical sensors. Light: Sci. Appl. 2014, 3, e222. (33) Su, Y. H.; Ke, Y.-F.; Cai, S.-L.; Yao, Q.-Y. Surface plasmon resonance of layer-by-layer

gold

nanoparticles

induced

photoelectric

current

in

environmentally-friendly plasmon-sensitized solar cell, Light: Sci. Appl. 2012, 1, e14. (34) Chen, X.; Jia, B.;

Zhang, Y.; Gu, M. Exceeding the limit of plasmonic light

trapping in textured screen-printed solar cells using Al nanoparticles and wrinkle-like graphene sheets, Light: Sci. Appl. 2013, 2, e92. (35) Li, X.; Ren, X.; Xie, F.; Zhang, Y.; Xu, T.; Wei, B.; Choy, W. C. H. 17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

High-Performance Organic Solar Cells with Broadband Absorption Enhancement and Reliable Reproducibility Enabled by Collective Plasmonic Effects. Adv. Opt. Mater. 2015, 3, 1220-1231. (36) Fan, X.; Zheng, W.; Singh, D., Light scattering and surface plasmons on small spherical particles. Light: Sci. Appl. 2014, 3, e179. (37) Pors, A.; Nielsen, M. G.; Bernardin, T.; Weeber, J.-C.; Bozhevolnyi, S. I. Efficient unidirectional polarization-controlled excitation of surface plasmon polaritons. Light: Sci. Appl. 2014, 3, e197. (38) Kawawaki, T.; Wang, H.; Kubo K.; Saito K.; Nakazaki, J.; Segawa, H.; Tatsuma, T. Efficiency Enhancement of PbS Quantum Dot/ZnO Nanowire Bulk-Heterojunction Solar Cells by Plasmonic Silver Nanocubes. ACS Nano 2015, 9, 4165-4172. (39) Jefferies, J.; Sabat, R. G. Surface-Relief Diffraction Gratings' Optimization for Plasmonic Enhancements in Thin-Film Solar Cells. Prog. Photovolt: Res. Appl. 2014, 22, 648-655. (40) Atwater, H. A.; Polman, A. Plasmonics for Improved Photovoltaic Devices. Nat. Mater. 2010, 9, 205-213. (41) Li, J.; Cushing, S. K.; Meng, F.; Senty, T. R.; Bristow, A. D.; Wu, N. Plasmon-Induced Resonance Energy Transfer for Solar Energy Conversion. Nat. Photonics 2015, 9, 601-607. (42) Kozanoglu, D.; Apaydin, D. H.; Cirpan, A.; Esenturk, E. N. Power Conversion Efficiency Enhancement of Organic Solar Cells by Addition of Gold Nanostars, Nanorods, and Nanospheres. Org. Electron. 2013, 14, 1720-1727. 18


Page 18 of 27

Page 19 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(43) Xu, P.; Shen, L.; Meng, F.; Zhang, J.; Xie, W.; Yu, W.; Guo, W.; Jia, X.; Ruan, S. The Role of Ag Nanoparticles in Inverted Polymer Solar Cells: Surface Plasmon Resonance and Backscattering Centers. Appl. Phys. Lett. 2013, 102, 123301-123304. (44) Guo, C.; Sun, T.; Cao, F.; Liu, Q.; Ren, Z. Metallic Nanostructures for Light Trapping in Energy-Harvesting Devices. Light: Sci. Appl. 2014, 3, e161. (45) Yang, Y.; Feng, S.; Li, M.; Wu, Z.; Fang, X.; Wang, F.; Geng, D.; Yang, T.; Li, X.; Sun, B.; Gao, X. Structure, Optical Absorption, and Performance of Organic Solar Cells Improved by Gold Nanoparticles in Buffer Layers. ACS Appl. Mater. Interfaces 2015, 7, 24430-24437. (46) Schwartzkopf, M.; Buffet, A.; Korstgens, V.; Metwalli, E.; Schlage, K.; Benecke, G.; Perlich, J.; Rawolle, M.; Rothkirch, A.; Heidmann, B.; Herzog, G.; Muller-Buschbaum, P.; Rohlsberger, R.; Gehrke, R.; Stribeck, N.; Roth, S. V. From Atoms to Layers: in Situ Gold Cluster Growth Kinetics during Sputter Deposition. Nanoscale 2013, 5, 5053-5062. (47) Santoro, G.; Yu, S.; Schwartzkopf, M.; Zhang, P.; Koyiloth Vayalil, S.; Risch, J. F. H.; Rübhausen, M. A.; Hernández, M.; Domingo, C.; Roth, S. V. Silver Substrates for Surface Enhanced Raman Scattering: Correlation between Nanostructure and Raman Scattering Enhancement. Appl. Phys. Lett. 2014, 104, 243107-243113. (48) Schwartzkopf, M.; Santoro, G.; Brett, C. J.; Rothkirch, A.; Polonskyi, O.; Hinz, A.; Metwalli, E.; Yao, Y.; Strunskus, T.; Faupel, F.; Muller-Buschbaum, P.; Roth, S. V. Real-Time Monitoring of Morphology and Optical Properties during Sputter Deposition for Tailoring Metal-Polymer Interfaces. ACS Appl. Mater. Interfaces 2015, 19



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 27

7, 13547-13556. (49) Yao, M.; Jia, X.; Liu, Y.; Guo, W.; Shen, L.; Ruan, S. Surface Plasmon Resonance Enhanced Polymer Solar Cells by Thermally Evaporating Au into Buffer Layer. ACS Appl. Mater. Interfaces 2015, 7, 18866-18871. (50) Liu, C.-M.; Chen, C.-M.; Su, Y.-W.; Wang, S.-M.; Wei, K.-H. The Dual Localized Surface Plasmonic Effects of Gold Nanodots and Gold Nanoparticles Enhance the Performance of Bulk Heterojunction Polymer Solar Cells. Org. Electron. 2013, 14, 2476-2483. (51) Li, X.; Xie, F.; Zhang, S.; Hou, J.; Choy, W., MoOx and V2Ox as hole and electron transport layers through functionalized intercalation in normal and inverted organic optoelectronic devices. Light: Sci. Appl. 2015, 4, e273. (52) Bao, X.; Zhu, Q.; Wang, T.; Guo, J.; Yang, C.; Yu, D.; Wang, N.; Chen, W.; Yang, R.

Simple

O2

plasma-processed

V2O5

as

an

Anode

Buffer Layer

for

High-Performance Polymer Solar Cells. ACS Appl. Mater. Interfaces 2015, 7, 7613-7618. (53) Qiu, M.; Zhu, D.; Bao, X.; Wang, J.; Wang, X.; Yang, R. WO3 with Surface Oxygen Vacancies as an Anode Buffer Layer for High Performance Polymer Solar Cells. J. Mater. Chem. A 2016, 4, 894-900. (54) Zhu, J.; Li, J.-j.; Zhao, J.-w. The Study of Surface Plasmon Resonance in Au-Ag-Au Three-Layered Bimetallic Nanoshell: The Effect of Separate Ag Layer. Plasmonics 2013, 9, 435-441. (55) Qian, L.; Yang, X. Preparation and Characterization of Ag (Au) Bimetallic 20


Page 21 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Core–Shell Nanoparticles with New Seed Growth Method. Colloids and Surfaces A: Physicochem. Eng. Aspects 2005, 260, 79-85. (56) Wu, J.-H.; Chen, F.-C.; Hsiao, Y.-S.; Chien, F.-C.; Chen, P.; Kuo, C.-H.; Huang, M., H.; Hsu, C.-S. Surface Plasmonic Effects of Metallic Nanoparticles on the Performance of Polymer Bulk Heterojunction Solar Cells. ACS Nano 2011, 5, 959-967. (57) Chen, H. C.; Lin, S. W.; Jiang, J. M.; Su, Y. W.; Wei, K. H. Solution-Processed Zinc Oxide/Polyethylenimine Nanocomposites as Tunable Electron Transport Layers for Highly Efficient Bulk Heterojunction Polymer Solar Cells. ACS Appl. Mater. Interfaces 2015, 7, 6273-6281.

21



Figures

(b)

(a)

Figure 1. (a) Device structure of the inverted PSCs by thermally evaporating Ag and Au NPs into WO3 layer. (b) AFM topography image (1 × 1 µm2) of the WO3/Ag/Au.

60 50 40 30 20

(b)

10 0 300

80

Device B Device C Device D Device E

70 60

IPCE(%)

Device A0 Device A1 Device A2 Device A3

(a) 70 IPCE(%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 27

50 40 30 20 10

400

500

600

700

800

0 300

400

Wavelength(nm)

500

600

700

Wavelength(nm)

Figure 2. IPCE spectra in the wavelength range from 300 to 800 nm. (a) The devices A0-A3. (b) The devices B-E.

22


800

2

8 Device A Device B Device C Device D Device E

4 0 -4 -8 -12

-0.4 -0.2 0.0

0.2

0.4

0.6

0.8

1.0

Voltage(V) Figure 3. J-V characterization of devices A-E tested under AM1.5G solar illuminations with an intensity of 100 mW cm-2.

70

Transmittance(%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Current density(mA/cm )

Page 23 of 27

60 50 40

Devices without top electrode B C D E

30 20 10 0

400

500

600

700

800

Wavelength(nm) Figure 4. Transmittance spectra of devices B-E without top Ag electrode in the wavelength range from 300 to 800 nm.

23



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(a) Ag contact angle=60.02° °

(b) Au contact angle=66.31° °

(c) WO3 contact angle=38.39 °

Figure 5. The contact angles of the ethylene glycol on the surface of (a) Ag, (b) Au and (c) WO3 films.

Figure 6. PL spectra of P3HT tested using an excitation source wavelength (λexc) of 470 nm.

24


Page 24 of 27

Page 25 of 27

(a)

(b)

Figure 7. UPS spectra around the secondary electron cut-off and the Fermi energy of WO3 with or without different thickness Ag and Au. (a) 2 nm and 5 nm-thick Ag. (b) Energy structure of the thermally evaporated WO3/Ag (2nm, 4nm) interface.

120 Device B Device C

100

ImZ″(Ω• cm2)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


80 60 40 20 0

0

50

100 150 ReZ′(Ω•cm2)

200

Figure 8. Complex impedance spectra of the devices B and C. .

25



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 27

Table 1. Detail performance parameter under 100 mW cm-2 simulated AM1.5G in ambient air with different thickness of Ag and Au. Device styles

Jsc (mA cm-2)

Voc (V)

FF (%)

PCE (%)

Rs (Ω)

Rsh (Ω)

A

7.91±0.14

0.87±0.01

64.6±0.2

4.57±0.16

154.58

37257.15

B

9.66±0.13

0.87±0.01

66.3±0.2

5.71±0.14

141.56

57645.11

C

11.01±0.12

0.87±0.01

67.6±0.2

6.55±0.12

126.21

70957.45

D

10.43±0.13

0.87±0.01

67.1±0.2

6.15±0.13

140.21

62841.25

E

7.14±0.12

0.86±0.01

63.9±0.2

4.01±0.18

189.36

12257.35

26


Page 27 of 27

For Table of Contents only

Electric field

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Light wave Ag

Au

Ag

Au

27


Performance Improvement of Polymer Solar Cells by Surface-Energy

Recommend Documents