Hybrid Organic Tandem Solar Cell Comprising Small-Molecule Bottom and Polymer:Fullerene Top Subcells Fabricated by Thin-Film Transfer

Ka, Yoonseok; Hwang, Hong Jin; Kim, Changsoon

doi:10.1038/s41598-017-02181-6

Cited by 15 publications

(6 citation statements)

References 40 publications

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“…In 2017, Ka et al demonstrated an example of device fabricated in this fashion. In their work, they deposited a front cell consisting of the small molecular donor TAPC blended with C 70 . Next in the stack they deposited, also by thermal evaporation, a PTCBI:C 70 buffer electron transport layer, preceding a PTCBI/Ag/HAT‐CN interconnecting layer.…”

Section: Tandem Solar Cellsmentioning

confidence: 99%

Advances in Solution‐Processed Multijunction Organic Solar Cells

2018

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Single-junction solar cells are principally limited in performance by two factors (Figure 1a). Electrons excited by photons with energy higher than the bandgap relax to the band edges, releasing surplus energy as heat (thermalization loss). Photons with energy lower than the bandgap are not absorbed (transmission loss). These losses can be alleviated with two or more absorber layers. The first layer should feature a wide bandgap material to reduce the thermalization loss for high-energy photons. The second layer should have a lower bandgap to absorb the low-energy photons that pass the first layer. In such configuration a tandem cell provides less thermalization and less transmission losses than each of the corresponding single-junction cells. In the detailed-balance limit, a double-junction (tandem) cell can reach an efficiency of 42% and a triple-junction cell 49%. [6] To construct a tandem cell, the two complementary absorber layers must be stacked optically and electrically ( Figure 1b). The interconnecting layer (ICL) between the two subcells must pass light and sustain the photocurrent by providing an optically transparent electrical contact for recombination of electrons and holes from the adjacent photoactive layers. The Fermi level of the hole-transporting layer (HTL) and the electron-transporting layer (ETL) that jointly form the ICL must match the relevant highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels in the adjacent photoactive layers (Figure 1b). The ICL should not cause voltage losses and have low resistance. The open-circuit voltage (V OC ) of the tandem solar cell is ideally the sum of the V OC s of the subcells and the photocurrent is limited by the subcell generating less current. To overcome the intrinsic performance limits of single-junction cells, the subcells should absorb complementary regions of the solar spectrum and generate equal photocurrent.In the first organic tandem solar cells, materials were thermally evaporated. Initially only metal clusters were used to interconnect the subcells, [7][8][9] later complemented by p-and n-doped organic transport layers. [10,11] In 2007, the first fully solution-processed tandem polymer solar cells were reported by Gilot et al. [12] and Kim et al. [13] In both examples the ICL featured a layer of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as HTL, stacked on top of either a zinc oxide or a titanium oxide layer as ETL. Kim et al. achieved a PCE of 6.5%. Since then PCEs have steadily increased. Major improvements involved the use of more efficient photoactive blends that afford a high V OC relative to their optical bandgap The efficiency of organic solar cells can benefit from multijunction device architectures, in which energy losses are substantially reduced. Herein, recent developments in the field of solution-processed multijunction organic solar cells are described. Recently, various strategies have been investigated and implemented to improve the performance of these device...

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Section: Tandem Solar Cellsmentioning

confidence: 99%

Advances in Solution‐Processed Multijunction Organic Solar Cells

2018

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“…It is well known that p–i–n OPV solar cells show better performance and are more stable due to the thicker p-doped hole transport layer (HTL) and the n-doped electron transport layer (ETL) with low series resistances. In a series of papers, − p- and n-type electronic doping of organic donor (D) and acceptor (A) transport layers has been shown to increase the performance of small-molecule OPV cells, and 8–10% efficiency has been achieved in tandems, demonstrating a great promise of p–i–n organic structures. − …”

Section: Introductionmentioning

confidence: 99%

Ionically Gated Small-Molecule OPV: Interfacial Doping of Charge Collector and Transport Layer

Saranin

Mahmoodpoor

Voroshilov

et al. 2021

ACS Appl. Mater. Interfaces

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We demonstrate an improvement in the performance of organic photovoltaic (OPV) systems based on small molecules by ionic gating via controlled reversible n-doping of multi-wall carbon nanotubes (MWCNTs) coated on fullerene electron transport layers (ETLs): C60 and C70. Such electric double-layer charging (EDLC) doping, achieved by ionic liquid (IL) charging, allows tuning of the electronic concentration in MWCNTs and the fullerene planar acceptor layers, increasing it by orders of magnitude. This leads to the decrease of the series and increase of the shunt resistances of OPVs and allows use of thick (up to 200 nm) ETLs, increasing the durability of OPVs. Two stages of OPV enhancement are described upon the increase of gating bias V g: at small (or even zero) V g, the extended interface of ILs and porous transparent MWCNTs is charged by gating, and the fullerene charge collector is significantly improved, becoming an ohmic contact. This changes the S-shaped J–V curve via improving the electron collection by an n-doped MWCNT cathode with an ohmic interfacial contact. The J–V curves further improve at higher gating bias V g due to the increase of the Fermi level and decrease of the MWCNT work function. At the next qualitative stage, the acceptor fullerene layer becomes n-doped by electron injection from MWCNTs while ions of ILs penetrate into the fullerene. At this step, the internal built-in field is created within OPV, which helps in exciton dissociation and charge separation/transport, increasing further the J sc and the fill factor. The ionic gating concept demonstrated here for most simple classical planar small-molecule OPV cells can be potentially applied to more complex highly efficient hybrid devices, such as perovskite photovoltaic with an ETL or a hole transport layer, providing a new way to tune their properties via controllable and reversible interfacial doping of charge collectors and transport layers.

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“…Ka et al adopted stamping methodology, eliminating solution requirements. [ 93 ] The top subcell utilizing small‐molecule BHJs was first fabricated via spin coating over poly(dimethylsiloxane) (PDMS) stamp and subsequently dried at high‐vacuum‐eliminating additives. Then, the top subcell was transferred to the bottom subcell on ITO by stamping after mild temperature annealing, governing conformal interaction at the interface.…”

Section: Processing Issue In Otscsmentioning

confidence: 99%

Recent Developments in Organic Tandem Solar Cells toward High Efficiency

Ullah

Chen

Choy

2021

Adv Energy and Sustain Res

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The demands of sustainable energy sources and depletion of conventional energy sources have accelerated the quest for attaining nontoxic and low‐cost organic solar cells (OSCs). The intrinsic characteristics of organic semiconductor materials such as light weight, mechanical stability, tailorable bandgaps, and ease of solution processability on a large area with flexible devices provide new dimensions to the device engineers toward sustainable electronic technologies. The past two decades have witnessed an inspiring breakthrough of device efficiency by developing multijunction architectures. The significance of organic tandem solar cells (OTSCs) does not only elevate the efficiencies but also considerably reduces the absorption losses. Herein, the recent developments in OTSCs, starting from designing rules for OTSCs, followed by implementation of the interconnecting layer (ICL) structure, and issues regarding processing, light management, and engaging photoactive materials for constructing OTSCs, are comprehensively described. Finally, the conclusion and outlook for OTSCs are provided.

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Hybrid Organic Tandem Solar Cell Comprising Small-Molecule Bottom and Polymer:Fullerene Top Subcells Fabricated by Thin-Film Transfer

Cited by 15 publications

References 40 publications

Advances in Solution‐Processed Multijunction Organic Solar Cells

Advances in Solution‐Processed Multijunction Organic Solar Cells

Ionically Gated Small-Molecule OPV: Interfacial Doping of Charge Collector and Transport Layer

Recent Developments in Organic Tandem Solar Cells toward High Efficiency

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