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1.
ACS Appl Mater Interfaces ; 12(2): 2313-2318, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31840973

RESUMO

Tandem cells are one of the most effective ways of breaking the single junction Shockley-Queisser limit. Solution-processable phosphate-buffered saline (PbS) quantum dots are good candidates for producing multiple junction solar cells because of their size-tunable band gap. The intermediate recombination layer (RL) connecting the subcells in a tandem solar cell is crucial for device performance because it determines the charge recombination efficiency and electrical resistance. In this work, a solution-processed ultrathin NiO and Ag nanoparticle film serves as an intermediate layer to enhance the charge recombination efficiency in PbS QD dual-junction tandem solar cells. The champion devices with device architecture of indium tin oxide/S-ZnO/1.45 eV PbS-PbI2/PbS-EDT/NiO/Ag NP/ZnO NP/1.22 eV PbS-PbI2/PbS-EDT/Au deliver a 7.1% power conversion efficiency, which outperforms the optimized reference subcells. This result underscores the critical role of an appropriate nanocrystalline RL in producing high-performance solution-processed PbS QD tandem cells.

2.
Adv Mater ; 31(52): e1904601, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31721329

RESUMO

The use of a ternary active layer offers a promising approach to enhance the power conversion efficiency (PCE) of polymer solar cells (PSCs) via simply incorporating a third component. Here, a ternary PSC with improved efficiency and stability facilitated by a new small molecule IBC-F is demonstrated. Even though the PBDB-T:IBC-F-based device gives an extremely low PCE of only 0.21%, a remarkable PCE of 15.06% can be realized in the ternary device based on PBDB-T:IE4F-S:IBC-F with 20% IBC-F, which is ≈10% greater than that (PCE = 13.70%) of the control binary device based on PBDB-T:IE4F-S. The improvement in the device performance of the ternary PSC is mainly attributed to the enhancement of fill factor, which is due to the improved charge dissociation and extraction, suppressed bimolecular and trap-assisted recombination, longer charge-carrier lifetime, and enhanced intermolecular interactions for preferential face-on orientation. Additionally, the ternary device with 20% IBC-F shows better thermal and photoinduced stability over the control binary device. This work provides a new angle to develop the third components for building ternary PSCs with enhanced photovoltaic performance and stability for practical applications.

3.
ACS Appl Mater Interfaces ; 10(49): 42397-42405, 2018 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-30422618

RESUMO

It is well known that tailoring the interfacial structure is very important for perovskite solar cells, especially for its performance and stability. Here, we report a universal and versatile method of modulating the energetic alignment between the perovskite and hole-transporting layer by introducing a multifunctional dipole layer based on metallophthalocyanine derivatives copperphthalocyanine (CuPc) or highly fluorinated copper hexadecafluorophthalocyanine (F16CuPc). Both molecules were introduced through an "antisolution" process to treat the surface of organic-inorganic CH3NH3PbI3 perovskite. The dipole layer can well align the interfacial energy levels, passivate the CH3NH3PbI3 surface, and fill the grain boundaries, resulting in greatly suppressed charge recombination. As a result, our planar CH3NH3PbI3 perovskite devices exhibit the best power conversion efficiency of 20.2%, with significantly enhanced open-circuit voltages ( Voc) of 1.112 V (CuPc) and 1.145 V (F16CuPc), which is a record high Voc value for CH3NH3PbI3 thin-film solar cells. More importantly, the use of highly fluorinated F16CuPc produces a significantly more hydrophobic surface, leading to drastically improved long-term stability under ambient conditions. We believe that our study offers a general approach to making multifunctional dipole layers, which are necessary for achieving both stable and efficient perovskite solar cells.

4.
ACS Nano ; 12(7): 7134-7140, 2018 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-29851458

RESUMO

Organic field-effect transistors (OFETs) that utilize ambipolar polymer semiconductors can benefit from the ability of both electron and hole conduction, which is necessary for complementary circuits. However, simultaneous hole and electron transport in organic field-effect transistors result in poor ON/OFF ratios, limiting potential applications. Solution processing methods have been developed to control charge transport properties and transform ambipolar conduction to hole-only conduction. The electron-acceptor phenyl-C61-butyric acid methyl ester (PC61BM), when mixed in solution with an ambipolar semiconducting polymer, can reduce electron conduction. Unipolar p-type OFETs with high, well-defined ON/OFF ratios and without detrimental effects on hole conduction are achieved for a wide range of blend compositions, from 95:5 to 5:95 wt % semiconductor polymer:PC61BM. When introducing the alternative acceptor N, N'-bis(1-ethylpropyl)-3,4:9,10-perylenediimide (PDI), high ON/OFF ratios are achieved for 95:5 wt % semiconductor polymer:PDI; however, electron conduction increases for 50:50 and 5:95 wt % semiconductor polymer:PDI. As described within, we show that electron conduction is practically eliminated when additive domains do not percolate across the OFET channel, that is, electrons are "morphologically trapped". Morphologies were characterized by optical, electron, and atomic force microscopy as well as X-ray scattering techniques. PC61BM was substituted with an endohedral Lu3N fullerene, which enhanced contrast in electron microscopy and allowed for more detailed insight into the blend morphologies. Blends with alternative, nonfullerene acceptors further emphasize the importance of morphology and acceptor percolation, providing insights for such blends that control ambipolar transport and ON/OFF ratios.

5.
ACS Appl Mater Interfaces ; 10(28): 24037-24045, 2018 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-29944828

RESUMO

The adoption of neat-fullerene (C60 and C70) in polymer solar cells offers opportunities to develop cost-effective and thermally stable devices. Here, through rational side-chain engineering of low optical-gap polymer poly(benzodithiophene-furan-diketopyrrolopyrrole)s (PBDs), we demonstrated for the first time a polymer/C70 blend exhibited higher efficiency (best 6.1%) compare to their polymer/[70]PCBM (best 5.7%) counterparts, and the best efficiency is at the front of efficient polymer/neat-fullerene solar cells. More importantly, we first demonstrated the morphology optimization methodology for solution-processed polymer/neat-fullerene blends in order to reduce the strong crystallization and aggregation of neat-fullerene molecules. In comparison with previous work, these results can provide not only material design strategy but also fundamental difference between polymer/neat-fullerene and polymer/PCBM blend morphology, which allow us better understanding of how to choose proper materials and optimize blend morphology in polymer/neat-fullerene based device to deliver higher photovoltaic performance.

6.
ACS Appl Mater Interfaces ; 10(3): 2776-2784, 2018 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-29314821

RESUMO

A widely applicable doping design for emerging nonfullerene solar cells would be an efficient strategy in order to further improve device photovoltaic performance. Herein, a family of compound TBAX (TBA= tetrabutylammonium, X = F, Cl, Br, or I, containing Lewis base anions are considered as efficient n-dopants for improving polymer-polymer solar cells (all-PSCs) performance. In all cases, significantly increased fill factor (FF) and slightly increased short-circuit current density (Jsc) are observed, leading to a best PCE of 7.0% for all-PSCs compared to that of 5.8% in undoped devices. The improvement may be attributed to interaction between different anions X- (X = F, Cl, Br, and I) in TBAX with the polymer acceptor. We reveal that adding TBAX at relatively low content does not have a significantly impact on blend morphology, while it can reduce the work function (WF) of the electron acceptor. We find this simple and solution processable n-type doping can efficiently restrain charge recombination in all-polymer solar cell devices, resulting in improved FF and Jsc. More importantly, our findings may provide new protocles and insights using n-type molecular dopants in improving the performance of current polymer-polymer solar cells.

7.
ACS Nano ; 11(7): 7215-7222, 2017 07 25.
Artigo em Inglês | MEDLINE | ID: mdl-28679036

RESUMO

Silicon-organic heterojunction solar cells suffer from a noticeable weakness of inefficient rear contact. To improve this rear contact quality, here, two solution-processed organic n-type donor-acceptor naphthalene diimide (NDI)-based conjugated polymers of N2200 and fluorinated analogue F-N2200 are explored to reduce the contact resistance as well as to passivate the Si surface. Both N2200 and F-N2200 exhibit high electron mobility due to their planar structure and strong intermolecular stacking, thus allowing them to act as excellent transporting layers. Preferential orientation of the polymers leads to reduce contact resistance between Si and cathode aluminum, which can enhance electron extraction. More importantly, the substitution of fluorine atoms for hydrogen atoms within the conjugated polymer can strengthen the intermolecular stacking and improve the polymer-Si electronic contact due to the existence of F···H interactions. The power conversion efficiencies of Si-PEDOT:PSS solar cells increased from 12.6 to 14.5% as a consequence of incorporating the F-N2200 polymer interlayers. Subsequently, in-depth density functional theory simulations confirm that the polymer orientation plays a critical role on the polymer-Si contact quality. The success of NDI-based polymers indicates that planar conjugated polymer with a preferred orientation could be useful in developing high-performance solution-processed Si-organic heterojunction photovoltaic devices.

8.
ACS Appl Mater Interfaces ; 9(27): 23181-23188, 2017 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-28627165

RESUMO

In this work, we demonstrate high-efficiency planar perovskite solar cells (PSCs), using room-temperature sputtered niobium oxide (Nb2O5) as the electron-transporting layer (ETL). Widely spread ETL-like TiO2 often requires high-temperature (>450 °C) sintering, which is not desired for the fabrication of flexible devices. The amorphous Nb2O5 (labeled as a-Nb2O5) ETL, without any heat treatment, can give a best power conversion efficiency (PCE) of 17.1% for planar PSCs. Interestingly, the crystalline Nb2O5 (labeled as c-Nb2O5), with high-temperature (500 °C) annealing, results in a very similar PCE of 17.2%, indicating the great advantage of a-Nb2O5 in energy saving. We thus carried out a systematical investigation on the properties of the a-Nb2O5 film. The Hall effect measurements indicate both high mobility and conductivity of the a-Nb2O5 film. Kelvin probe force microscopy measurements define the Fermi levels of a-Nb2O5 and c-Nb2O5 as -4.31 and -4.02 eV, respectively, which allow efficient electron extraction at the Nb2O5/perovskite interface, regardless of the additional heat treatment on Nb2O5 film. Benefitting from the low-temperature process, we further demonstrated flexible PSCs based on a-Nb2O5, with a considerable PCE of 12.1%. The room-temperature processing and relatively high device performance of a-Nb2O5 suggest a great potential for its application in optoelectrical devices.

9.
ACS Appl Mater Interfaces ; 9(15): 13396-13405, 2017 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-28368094

RESUMO

We have investigated a series of commercially available alkenyl carboxylic acids with different alkenyl chain lengths (trans-2-hexenoic acid (CA-6), trans-2-decenoic acid (CA-10), 9-tetradecenoic acid (CA-14)) for use as solvent additives in polymer-polymer non-fullerene solar cells. We systematically investigated their effect on the film absorption, morphology, carrier generation, transport, and recombination in all-polymer solar cells. We revealed that these additives have a significant impact on the aggregation of polymer acceptor, leading to improved phase segregation in the blend film. This in-depth understanding of the additives effect on the nanomorphology in all-polymer solar cell can help further boost the device performance. By using CA-10 with the optimal alkenyl chain length, we achieved fine phase separation, balanced charge transport, and suppressed recombination in all-polymer solar cells. As a result, an optimal power conversion efficiency (PCE) of 5.71% was demonstrated which is over 50% higher than that of the as-cast device (PCE = 3.71%) and slightly higher than that of devices with DIO treatment (PCE = 5.68%). Compared with widely used DIO, these halogen-free alkenyl carboxylic acids have a more sustainable processing as well as better performance, which may make them more promising candidates for use as processing additives in organic non-fullerene solar cells.

10.
Sci Rep ; 6: 26459, 2016 05 26.
Artigo em Inglês | MEDLINE | ID: mdl-27226354

RESUMO

In this work, we have reported for the first time an efficient all-polymer tandem cell using identical sub-cells based on P2F-DO:N2200. A high power conversion efficiency (PCE) of 6.70% was achieved, which is among the highest efficiencies for all polymer solar cells and 43% larger than the PCE of single junction cell. The largely improved device performance can be mainly attributed to the enhanced absorption of tandem cell. Meanwhile, the carrier collection in device remains efficient by optimizing the recombination layer and sub-cell film thickness. Thus tandem structure can become an easy approach to effectively boost the performance of current all polymer solar cells.

11.
ACS Appl Mater Interfaces ; 7(7): 3994-9, 2015 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-25636057

RESUMO

Inverted planar heterojunction perovskite solar cells employing different polymers, poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalene diimide-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (N2200), poly{[N,N'-bis(alkyl)-1,4,5,8-naphthalene diimide-2,6-diyl-alt-5,5'-di(thiophen-2-yl)-2,2'-(E)-2-(2-(thiophen-2-yl)vinyl)thiophene]} (PNVT-8), and PNDI2OD-TT as electron-transporting material (ETM) have been investigated for the first time. The best device performance was obtained when N2200 was applied as the ETM, with JSC of 14.70 mA/cm2, VOC of 0.84 V, and fill factor (FF) of 66%, corresponding to a decent power conversion efficiency (PCE) of ∼ 8.15%. Which is very competitive to the parameters (JSC 14.65 mA/cm2, VOC 0.83 V, FF 70%, and PCE 8.51%) of the reference device employing conventional PCBM as the ETM. The slightly lower FF could be mainly accounted for by the increased recombination in the polymer contained devices. This work demonstrated that polymeric materials can be used as efficient ETM in perovskite solar cells, and we believe this class of polymeric ETMs will further promote the performance of perovskite photovoltaic cells after extended investigation.

13.
Nanotechnology ; 24(48): 484010, 2013 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-24196589

RESUMO

In this work, we have reported for the first time a facile route for developing solution-processed Al2O3 film at a greatly reduced processing temperature and studied its applications in producing inverted polymer solar cells (PSCs). These PSCs using Al2O3 thin film as the electron-extraction layer demonstrated improved diode characteristics and achieved a 20% higher power conversion efficiency than devices using the conventional ZnO buffer layer. Furthermore, the low temperature processing of the Al2O3 film makes it compatible with fabrication of flexible organic electronic devices based on plastic substrates.

14.
Adv Mater ; 25(40): 5772-8, 2013 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-23934968

RESUMO

Solution-processed hybrid solar cells employing a low band-gap polymer and PbSx Se1-x alloy nanocrystals, achieving a record high PCE of 5.50% and an optimal FF of 67% are presented. The remarkable device efficiency can be attributed to the high-performance active materials, the optimal polymer/NCs ratio and, more importantly, the vertical donor/(donor:acceptor)/acceptor structure which benefits charge dissociation and transport.


Assuntos
Nanopartículas/química , Polímeros/química , Energia Solar , Ligas/química , Elétrons , Fluoretos/química , Compostos de Lítio/química , Poliestirenos/química , Teoria Quântica , Tiofenos/química , Compostos de Estanho/química
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