hybrid organic/inorganic thin-film multijunction solar cells exceeding 11% power conversion...

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1wileyonlinelibrary.com

CO

MM

UN

ICATIO

N

Hybrid Organic/Inorganic Thin-Film Multijunction Solar Cells Exceeding 11% Power Conversion Effi ciency

Steffen Roland , Sebastian Neubert , Steve Albrecht , Bernd Stannowski , Mark Seger , Antonio Facchetti , Rutger Schlatmann , Bernd Rech , and Dieter Neher*

S. Roland, S. Albrecht, Prof. D. Neher University of Potsdam Institute of Physics and Astronomy Physik weicher Materie Karl-Liebknecht-Str. 24/25 14476 Potsdam , Germany E-mail: [email protected] S. Neubert, Dr. B. Stannowski, Prof. R. Schlatmann PVcomB/Helmholtz-Zentrum Berlin für Materialien und Energie GmbH Schwarzschildstr. 3 , 12489 Berlin , Germany Dr. M. Seger, Prof. A. Facchetti Polyera Corporation Skokie , IL 60077 , USA Prof. B. Rech Helmholtz-Zentrum Berlin für Materialien und Energie GmbH Kekuléstr. 5 , 12489 Berlin , Germany

DOI: 10.1002/adma.201404698

trapping architectures in order to effi ciently absorb low-energy photons. These considerations have drawn the attention to fab-ricate thin-fi lm hybrid multijunction architectures comprising a high bandgap a-Si:H front subcell and a low bandgap organic back subcell. [ 10–13 ] While the PCEs for such double junction (DJ) devices was initially quite low (≈1.8%), [ 10 ] they have quad-rupled over the last three years, now reaching more than 7.5% PCE. [ 12,13 ] This progress was mainly achieved due to new, low bandgap donor polymers, and a thorough tuning of the sub-cell contacts to establish an effi cient series connection between the front and the back cell. However, a careful analysis of these cells revealed a limited spectral coverage of the solar spectrum in the wavelength range around 600 nm (where the sun spec-trum provides the highest number of photons).

In this study, we show that by including another a-Si:H sub-cell, thus combining a p-i-n/p-i-n a-Si:H inorganic DJ with a low bandgap polymer:fullerene bulk heterojunction back-cell, highly effi cient hybrid triple junction (TJ) devices can be real-ized, with PCE exceeding 11%. Additionally, this a-Si:H/a-Si:H confi guration is known to be less affected by light induced degradation. [ 14 ] Noteworthy, this concept merges the well-established a-Si:H coating technology and the solution-based processing of organic solar cells. Furthermore, the high absorp-tion coeffi cients of a-Si:H and the use of organic materials enable the fabrication of “truly thin-fi lm” solar cells, with the total thickness of the entire active stack being less than 1 µm. Other effi cient hybrid concepts incorporating n-type single crystal silicon and organic layers show fi lm thicknesses of several hundred micrometers due to the use of single crystal silicon wafers. [ 15 ] Finally, due to the insolubility of a-Si:H in all common organic solvents or water, multilayer production without intermixing problems at the interfaces is achieved, allowing for future large-scale production. For example, roll-to-roll processing of the organic layers on the a-Si:H subcells. Low cost roll-to-roll processing is especially interesting as it has been shown by several industrial consortia in the past that high quality a-Si:H/µc-Si:H-based devices (including doped metal oxide contact layers) can cost effectively be deposited in a roll-to-roll production line including plasma-enhanced chemical vapor deposition (PECVD) and sputtering equipment. [ 16,17 ] The thick µc-Si:H layer could be replaced in such a process with the solution-processed organic layer.

To motivate this work, the absorption spectra of the subcells’ active layers in either a a-Si:H/organic DJ or the new TJ struc-ture, calculated via a transfer matrix formalism, are compared in Figure 1 a,b. The respective active layer fi lm thicknesses of 100/90 and 65/400/140 nm were chosen according to our pre-vious DJ record cell [ 12 ] and the best performing TJ presented in this work, respectively. The introduction of the a-Si:H middle

Over the last decade, a variety of p-conjugated molecules and polymers were developed enabling new approaches to fabri-cate cost-effective, organic thin-fi lm solar cells. Especially, all-organic multijunction solar cells based on conjugated polymers and/or small molecules have reproducibly-enabled power con-version effi ciencies (PCE) of over 11%. [ 1–3 ] These multijunction architectures combine subcells with complementary absorp-tion to overcome the inherent limitations of single junction (SJ) solar cells such as incomplete spectral coverage and/or thermalization losses. The diversity of organic materials with respect to their absorption onset energy, combined with very high absorption coeffi cients, renders these materials ideal can-didates for applications in multijunction solar cells. However, although tremendous progress has been made in realizing effi cient all-organic or all-inorganic multijunction solar cells, only a few attempts have been made to merge the benefi cial properties of both approaches in the so-called hybrid multijunc-tion solar cells. [ 4 ] Hydrogenated amorphous silicon (a-Si:H) is a widely known inorganic wide bandgap semiconductor which has been successfully implemented in several commercial elec-tronic and optoelectronic devices. [ 5 ] Commercially available SJ solar cells based on a-Si:H reach PCEs between 7% and 8%, whereas record cells have shown PCEs above 10%. [ 6,7 ] With an absorption onset at around 730 nm, a-Si:H is a well-established front cell material for multijunction solar cells, in particular in combination with hydrogenated microcrystalline silicon (µc-Si:H). [ 8 ] However, µc-Si:H is an indirect semiconductor and suffers from small absorption coeffi cients in the near-infrared (NIR) spectral range. [ 9 ] This leads to the need of depositing a rather thick µc-Si:H layer (typically >1 µm at low deposi-tion rates of about 0.5 nm s −1 ) and the incorporation of light

Adv. Mater. 2015, DOI: 10.1002/adma.201404698

www.advmat.dewww.MaterialsViews.com

http://doi.wiley.com/10.1002/adma.201404698

2 wileyonlinelibrary.com © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

CO

MM

UN

ICATI

ON

cell leads to a considerable absorption enhancement at inter-mediate wavelengths (500–700 nm). This offers the prospect for more effi cient photon harvesting. Given the higher internal quantum effi ciency (IQE) of a-Si:H compared to organic solar cells, [ 18–20 ] and the expected increase of the V OC by almost 0.9 eV without deterioration of the fi ll factor (FF) we expect a signifi cant increase of the overall PCE.

A schematic representation of the TJ architecture is dis-played in Figure 1 c. The a-Si:H subcells are deposited on a 800-nm thick sputtered aluminum-doped zinc oxide (AZO) fi lm, which provides high transparency and good conductivity,

and acts as transparent front contact. [ 21 ] The p-i-n a-Si:H-based subcells are prepared by PECVD (detailed description of pro-cessing can be found in the Supporting Information). The electrical series connection of the two a-Si:H subcells is estab-lished by a tunnel recombination junction between the heavily n-doped layer of the front cell and the heavily p-doped layer of the middle cell. The back contact of the inorganic tandem stack is formed by sputtering a transparent oxide conductor through a shadow mask on top of the a-Si:H middle cell (either a 130-nm thick indium tin oxide (ITO) layer or a 100-nm thick AZO layer). The front contact of the organic subcell comprises



Figure 1. Simulated absorption spectra for the individual subcells in a) an optimized a-Si:H/organic (Si-PCPDTBT:PCBM) DJ; and b) an optimized a-Si:H/a-Si:H/organic (Si-PCPDTBT:PCBM) TJ. Subcell absorption spectra of the front a-Si:H (blue) the middle a-Si:H (orange) and the organic back cell (red). The sum of the subcell absorption spectra is denoted in black. c) Schematic representation of the layer stack including a SEM cross-section of the TJ solar cell and the band structure. The scheme is shown for a cell based on an ITO/PEDOT recombination contact. d) Chemical structures of the applied low bandgap donor polymers (see full chemical name in the Supporting Information). e) Measured EQE of organic SJ solar cells comprising of Si-PCPDTBT or PMDPP3T (both 140-nm thick and with PC 60 BM as acceptor).

3wileyonlinelibrary.com© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

CO

MM

UN

ICATIO

N

either a 10-nm molybdenum trioxide (MoO 3 ) layer on top of a very thin (1 nm) silver layer, or a 30-nm thick layer of the transparent conducting polymer PEDOT:PSS (see Supporting Information) coated on AZO or ITO, respectively. These layer combinations were previously shown to form an effi cient recombination contact in hybrid DJs and each recombination contact has been optimized according to our previous publica-tion in order to achieve high FFs. [ 12 ] Two different low bandgap donor polymers, Si-PCPDTBT [ 20 ] and PMDPP3T [ 18 ] (for chemical structure see Figure 1 d) were used in combination with PC 60 BM as organic subcell. PC 60 BM was used instead of

PC 70 BM because of the weaker spectral overlap with the a-Si:H absorption. In organic SJs, these blends showed high external quantum effi ciencies (EQE) over a wide spectral range, up to 800 and 850 nm, respectively (Figure 1 e), while giving a V OC of about 0.6 V for both donor polymers ( Table 1 ). To build the full TJ device, the organic layers were deposited by spin-coating onto the inorganic layer stack (for details, see Supporting Infor-mation). As the inorganic layer stack is insoluble in organic solvents and water, intermixing of the layers is prevented and well-defi ned interfaces are achieved. The devices are completed by depositing 10-nm calcium and 1-µm silver to form the back contact, both metals are prepared by thermal evaporation through a shadow mask (see the Supporting Information for more information).

To fi nd the optimum fi lm thickness of each active layer, optical modeling was performed on the TJ layer stack, taking into account the optical constants of every layer (see Sup-porting Information). By assuming an IQE of one for the a-Si:H layers [ 19 ] and 0.8 for each organic solar cell, [ 18,20 ] the generated current density of each active layer can be simu-lated for all thickness combinations. Non-geminate recombi-nation was neglected in these calculations, meaning that the simulated photocurrents approximate short-circuit conditions. This assumption is justifi ed as the FFs of the subcells are suf-fi ciently large. Figure 2 displays contour plots of J SC of the TJ for a fi xed a-Si:H middle cell thickness of 400 nm with a ITO/PEDOT:PSS recombination contact and Si-PCPDTBT:PCBM (a) or PMDPP3T:PCBM (b) forming the organic back cell. The color coding is the same for both (a) and (b). Since both inor-ganic subcells consist of a-Si:H with the same extinction coef-fi cient, a rather thin a-Si:H front cell is needed to transmit a suffi ciently large number of photons to the middle a-Si:H cell. For the middle cell, a thickness of 400 nm has been used, since this seems to be a good compromise between an effi cient light absorption and a high FF. Due to the fi eld-assisted carrier col-lection mechanism associated with the p-i-n design, for effi -cient a-Si:H devices, i.e., high FF, the i-layer thickness is lim-ited to typically below 400 nm. [ 22 ] According to the contour plots in Figure 2 , the highest J SC in the TJ can be achieved for an



Table 1. Average performance with root mean square deviations of: a) the a-Si:H/a-Si:H DJs with an ITO or AZO back contact layer capped with Ag; b) the Si-PCPDTBT:PCBM-based solar cells (SJ represents the organic SJs and TJ the hybrid TJs); c) the SJ and the TJ solar cells with PMDPP3T:PCBM. These TJs are prepared on a smooth or a rough front AZO. All the TJs are prepared either with an ITO/PEDOT:PSS (ITO) or AZO/Ag/MoO 3 (AZO) recombination contact between the middle and the back subcell.

Solar cell V OC [V]

J SC [mA cm −2 ] (JV / EQE / SIM)

FF [%]

PCE [%]

(a) a-Si:H/a-Si:H

DJ (ITO) 1.70 ± 0.01 6.93 ± 0.07 78.2 ± 0.2 9. 2 ± 0.1

DJ (AZO) 1.71 ± 0.01 6.95 ± 0.08 78.0 ± 0.5 9.3 ± 0.2

(b) Si-PCPDTBT

SJ 0.59 ± 0.01 13.24 ± 0.09 55.2 ± 0.4 4.2 ± 0.1

TJ (ITO) 2.27 ± 0.01 5.36 ± 0.02/5.16/5.59 77.6 ± 0.2 9.4 ± 0.1

TJ (AZO) 2.28 ± 0.01 5.45 ± 0.01/5.36/5.51 77.8 ± 0.2 9.7 ± 0.1

(c) PMDPP3T

SJ 0.62 ± 0.01 13.4 ± 0.2 55 ± 1 4.6 ± 0.2

TJ (ITO) 2.31 ± 0.01 5.82 ± 0.06/5.68/5.79 79.6 ± 0.2 10.7 ± 0.1

TJ (ITO) record 2.31 5.91 79.9 10.9

TJ (AZO) 2.31 ± 0.01 5.77 ± 0.04/5.70/5.73 77.3 ± 0.8 10.3 ± 0.2

TJ (ITO) rough 2.26 6.83 75.8 11.7

TJ (AZO) rough 2.29 6.80 73.8 11.5

Figure 2. Contour plots of the simulated photocurrent density generated in the TJ confi guration as function of the a-Si:H front and organic back cell thickness for a a-Si:H middle cell thickness fi xed to 400 nm. a) Si-PCPDTBT:PCBM as organic back cell. b) PMDPP3T:PCBM as organic back cell.


CO

MM

UN

ICATI

ON

a-Si:H front cell i-layer thickness of 65 nm and an organic sub-cell thicknesses from 140 to 150 nm for both polymer blends. Obviously, J SC of the TJ improves if PMDPP3T is used in the organic back cell, indicating the benefi t of the lower bandgap of this material compared to Si-PCPDTBT (see Figure 1 e). Knowing the optimized layer thicknesses, we were able to build TJ devices for both donor polymers and with either the AZO- or ITO-based recombination contact. Table 1 summarizes the average values for V OC , FF, PCE, and J SC for at least three solar cells for each material combination that did not show shunting problems. The J SC of the TJ is determined from the JV char-acteristics under AM 1.5G illumination with 100 mW cm −2 ( J SC ( JV )), calculated from the EQE measurement of the cur-rent limiting subcell ( J SC (EQE)), and taken from the optical modeling simulation of the complete stack ( J SC (SIM)). The JV measurements were performed using an aperture to accu-rately measure the current density of the TJ (see Figure 1 c) as described in the Supporting Information. The JV characteristics of the best TJs are displayed in Figure 3 a.

For these devices, the EQE spectrum of each subcell was measured by simultaneously saturating the respective other two subcells by LEDs with appropriate wavelengths (see Sup-porting Information). [ 23 ] The EQE-derived and JV -measured J SC values agree well for the presented multijunctions (Table 1 b,c). The minor discrepancy between J SC ( JV ) and J SC (EQE) can be reasoned with uncertainties in the EQE measurement, e.g., incomplete current saturation of the subcells (see Supporting Information). [ 23 ] We fi nd that the measured J SC agrees very well with the estimated current from the optical simulations, meaning that photocurrent losses are small at short circuit. In addition, the V OC of the TJ is only slightly lower than the sum of the V OC s of the respective subcells (Table 1 ), indicating a nearly loss-free recombination at the recombination contacts. All optimized TJ solar cells exhibit very high FFs up to 80%, although both types of organic SJ solar cells have a FF of about 55%. These high FFs are possible as the current through the TJ is always limited by the middle a-Si:H cell (see Figure 3 b and Figure S1, Supporting Information), therefore the low FF of the organic subcell does not impact the FF of the TJ [ 24 ] The current densities derived from the TJ EQE spectra for the middle a-Si:H subcells (Figure S2, Supporting Information and Figure 3 b, orange) are the J SC (EQE) values denoted for the full TJ in Table 1 as they show the lowest current densities of all subcells and therefore limit the current of the respective TJ. Despite the fact that the middle a-Si:H subcell always limits the current, we fi nd the current density of the TJ to be markedly higher when employing the PMDPP3T:PCBM blend instead of Si-PCPDTBT (see Figure 3 and Figure S2, Supporting Information). The increase in current densities for the TJs with PMDPP3T is at least 0.2 mA cm −2 (Table 1 ) and could be confi rmed by EQE measurements as well as optical simulations. This increase is accompanied by a shift in the absorption of the organic back-cell to longer wavelength, which renders the organic cell to be less absorptive at wavelengths between 550 and 650 nm, where the middle a-Si:H subcell shows the maximum EQE benefi tting from light passing the organic cell, being refl ected back and absorbed in the a-Si:H middle cell. The PCEs of the hybrid TJs all clearly outperform our previous hybrid DJ record of 7.6%. [ 12 ] The TJs based on Si-PCPDTBT:PCBM show a 24–27% increase in PCE compared to the former hybrid DJ record. For the PMDPP3T-based TJs the increase is even higher, 35% and 41% for AZO- and ITO-based recombination contacts, respectively, with a record effi ciency of 10.9% PCE for the ITO-based device. This result clearly demonstrates the benefi t of the presented hybrid TJ concept, in particular when utilizing low bandgap donor polymers.

To enable even higher current densities for the hybrid solar cells, light scattering can be introduced, e.g., by wet chem-ical etching in diluted HCl of the front AZO. This treatment increases surface roughness, which scatters the incoming light and therefore improves the absorption pathway in the active layers. [ 14,21,25 ] The current-limited middle a-Si:H subcell will particularly benefi t from enhanced absorption, because this cell mainly works at wavelengths (500–700 nm, Figure 3 b) for which the absorption coeffi cient of a-Si:H is low. Moreover, the application of a specifi c thermal postdeposition treatment to the front AZO decreases its overall parasitic absorption. [ 26–28 ] Figure 3 a shows the JV curve of TJs fabricated very recently on



Figure 3. a) JV characteristics of the best performing cells for all TJ confi gurations listed in Table 1 . b) EQE spectra of the TJs prepared on smooth front AZO with an ITO/PEDOT:PSS recombination contact for Si-PCPDTBT:PCBM or PMDPP3T:PCBM based organic back cells. Front cell (blue), middle cell (orange), and back cell (red).

5wileyonlinelibrary.com© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

CO

MM

UN

ICATIO

N



rough, thermally treated front AZO electrodes. These character-istics display a substantially higher (≈1 mA cm −2 ) short-circuit current density, providing solid proof for the benefi cial effect of light scattering on the hybrid TJ performance. As the current generated by the middle cell now approaches that of the organic blend, the overall fi eld dependence of the TJ photocurrent will be more affected by the lower FF of the organic back cell. Also a-Si:H-based devices tend to form local shunt paths when grown on rough substrates, particularly for devices with rather thin i-layers like the front cell used here, which might also cause a lower FF. [ 29 ] Fortunately, these effects reduce the FF of the com-plete TJ only slightly, by ca. 5% when a rough front AZO is used. Note that also slight modifi cations of the a-Si:H tandem struc-ture were applied to ensure a high V OC and current matching in the a-Si:H subcells on a rough AZO front electrode (see Sup-porting Information). Overall, light scattering of the front AZO leads to a substantial increase of the current density in these hybrid solar cells without losing much FF or V OC , resulting in devices with PCEs well above 11% (Table 1 ). Combining highly transparent, scattering front electrodes with new low bandgap donor polymers, that display effi cient light harvesting in the NIR as well as higher V OC values, [ 30,31 ] these hybrid devices have a short-term potential of PCEs reaching 13–14% with a J SC at about 8 mA cm −2 , FFs of 75% and V OC values exceeding 2.4 V. Furthermore, due to their high operating voltage, such cells could be highly attractive for water splitting. [ 32,33 ]

In conclusion, we reported hybrid triple junction cells with a maximum PCE of 11.7%, showing the benefi t of merging inor-ganic and organic thin-fi lm solar-cell technologies. This value is comparable to the best reported PCEs for solution-processed all-organic double and triple junction devices, [ 2,18 ] with the addi-tional benefi t that less attention needs to be paid to intermixing of the components at the interface. Due to well adjusted recom-bination contacts, the hybrid TJs reach very high FFs up to 80% and high V OC values of more than 2.3 V. Furthermore, the solu-tion processed organic subcell is fully compatible with vacuum processed a-Si:H-based devices, which are applicable for mass production. [ 34 ] Therefore, this study highlights the great poten-tial of combining inorganic and organic solar cells in thin-fi lm hybrid multijunction devices, demonstrating a well producible, thin-fi lm solar-cell device already exceeding 11% of PCE.

Supporting Information Supporting Information is available from the Wiley Online Library or from the author.

Acknowledgements The authors thank Sybille Allard and Ullrich Scherf from the University of Wuppertal for giving access to Si-PCPDTBT (synthesized by Konarka). This work was supported by the Federal Ministry of Education and Research (BMBF) within the project PVcomB (FKZ 03IS2151D) and by the Helmholtz Energy Alliance for Hybrid Photovoltaics.

Received: October 10, 2014 Revised: November 10, 2014

Published online:

[1] S. Rohr , Heliatek press release , http://www.heliatek.com/wp-con-tent/uploads/2013/01/130116_PR_Heliatek_achieves_record_cell_effi ency_for_OPV.pdf (accessed October 2014 ).

[2] C.-C. Chen , W.-H. Chang , K. Yoshimura , K. Ohya , J. You , J. Gao , Z. Hong , Y. Yang , Adv. Mater. 2014 , 26 , 5670 .

[3] X. Che , X. Xiao , J. D. Zimmerman , D. Fan , S. R. Forrest , Adv. Energy Mater. 2014 , 1 , 1400568 .

[4] Z. M. Beiley , M. D. McGehee , Energy Environ. Sci. 2012 , 5 , 9173 .

[5] R. A. Street , Hydrogenated Amorphous Silicon , Cambridge University Press , Cambridge, UK 1991 .

[6] S. Benagli , D. Borrello , E. Vallat , J. Meier , U. Kroll , J. Hötzel , J. Bailat , J. Steinhauser , M. Marmelo , G. Monteduro , L. Castens , in 24th Eur. Photovoltaic Solar Energy Conf. Hamburg, Germany 2009 , p. 2293 .

[7] M. A. Green , K. Emery , Y. Hishikawa , W. Warta , E. D. Dunlop , Prog. Photovoltaics: Res. Appl. 2014 , 22 , 1 .

[8] J. Meier , S. Dubail , R. Platz , P. Torres , U. Kroll , J. A. Anna Selvan , N. Pellaton Vaucher , C. Hof , D. Fischer , H. Keppner , R. Flückiger , A. Shah , V. Shklover , K. D. Ufert , Sol. Energy Mater. Sol. Cells 1997 , 49 , 35 .

[9] A. V. Shah , H. Schade , M. Vanecek , J. Meier , E. Vallat-Sauvain , N. Wyrsch , U. Kroll , C. Droz , J. Bailat , Prog. Photovoltaics: Res. Appl. 2004 , 12 , 113 .

[10] T. Kim , J. H. Jeon , S. Han , D. K. Lee , H. Kim , W. Lee , K. Kim , Appl. Phys. Lett. 2011 , 98 , 183503 .

[11] J. H. Seo , D.-H. Kim , S.-H. Kwon , M. Song , M.-S. Choi , S. Y. Ryu , H. W. Lee , Y. C. Park , J.-D. Kwon , K.-S. Nam , Y. Jeong , J.-W. Kang , C. S. Kim , Adv. Mater. 2012 , 24 , 4523 .

[12] S. Albrecht , B. Grootoonk , S. Neubert , S. Roland , J. Wördenweber , M. Meier , R. Schlatmann , A. Gordijn , D. Neher , Sol. Energy Mater. Sol. Cells 2014 , 127 , 157 .

[13] W. Qin , W. Yu , W. Zi , X. Liu , T. Yuan , D. Yang , S. Wang , G. Tu , J. Zhang , F. S. Liu , C. Li , J. Mater. Chem. A 2014 , 2 , 15303 .

[14] B. Rech , H. Wagner , Appl. Phys. A 1999 , 69 , 155 . [15] R. Liu , S.-T. Lee , B. Sun , Adv. Mater. 2014 , 26 , 6007 . [16] E. A. G. Hamers , M. N. van den Donker , B. Stannowski ,

R. Schlatmann , G. J. Jongerden , Plasma Processes Polym. 2007 , 4 , 275 .

[17] M. N. van den Donker , A. Gordijn , H. Stiebig , F. Finger , B. Rech , B. Stannowski , R. Bartl , E. A. G. Hamers , R. Schlatmann , G. J. Jongerden , Sol. Energy Mater. Sol. Cells 2007 , 91 , 572 .

[18] W. Li , A. Furlan , K. H. Hendriks , M. M. Wienk , R. A. J. Janssen , J. Am. Chem. Soc. 2013 , 135 , 5529 .

[19] K. Ding , T. Kirchartz , B. E. Pieters , C. Ulbrich , A. M. Ermes , S. Schicho , A. Lambertz , R. Carius , U. Rau , Sol. Energy Mater. Sol. Cells 2011 , 95 , 3318 .

[20] M. C. Scharber , M. Koppe , J. Gao , F. Cordella , M. A. Loi , P. Denk , M. Morana , H.-J. Egelhaaf , K. Forberich , G. Dennler , R. Gaudiana , D. Waller , Z. Zhu , X. Shi , C. J. Brabec , Adv. Mater. 2010 , 22 , 367 .

[21] J. Müller , B. Rech , J. Springer , M. Vanecek , Sol. Energy 2004 , 77 , 917 .

[22] A. Shah , Thin-Film Silicon Solar Cells , EPFL Press , Lausanne, Swit-zerland 2010 .

[23] J. Gilot , M. M. Wienk , R. A. J. Janssen , Adv. Funct. Mater. 2010 , 20 , 3904 .

[24] T. Ameri , G. Dennler , C. Lungenschmied , C. J. Brabec , Energy Environ. Sci. 2009 , 2 , 347 .

[25] O. Kluth , B. Rech , L. Houben , S. Wieder , G. Schöpe , C. Beneking , H. Wagner , A. Löffl , H. W. Schock , Thin Solid Films 1999 , 351 , 247 .

[26] F. Ruske , M. Roczen , K. Lee , M. Wimmer , S. Gall , J. Hüpkes , D. Hrunski , B. Rech , J.Appl. Phys. 2010 , 107 , 013708 .


CO

MM

UN

ICATI

ON



[27] M. Wimmer , F. Ruske , S. Scherf , B. Rech , Thin Solid Films 2012 , 520 , 4203 .

[28] S. Neubert , M. Wimmer , F. Ruske , S. Calnan , O. Gabriel , B. Stannowski , R. Schlatmann , B. Rech , Prog. Photovoltaics: Res. Appl. 2014 , 22 , 1285 .

[29] T. Söderström , F.-J. Haug , V. Terrazzoni-Daudrix , C. Ballif , J. Appl. Phys. 2008 , 103 , 114509 .

[30] W. Li , K. H. Hendriks , W. S. C. Roelofs , Y. Kim , M. M. Wienk , R. A. J. Janssen , Adv. Mater. 2013 , 25 , 3182 .

[31] L. Dou , C.-C. Chen , K. Yoshimura , K. Ohya , W.-H. Chang , J. Gao , Y. Liu , E. Richard , Y. Yang , Macromolecules 2013 , 46 , 3384 .

[32] J. Luo , J.-H. Im , M. T. Mayer , M. Schreier , M. K. Nazeeruddin , N.-G. Park , S. D. Tilley , H. J. Fan , M. Grätzel , Science 2014 , 345 , 1593 .

[33] M. G. Walter , E. L. Warren , J. R. McKone , S. W. Boettcher , Q. Mi , E. A. Santori , N. S. Lewis , Chem. Rev. 2010 , 110 , 6446 .

[34] A. Shah , E. Moulin , C. Ballif , Sol. Energy Mater. Sol. Cells 2013 , 119 , 311 .

hybrid organic/inorganic thin-film multijunction solar cells exceeding 11% power conversion...

Documents