Understanding the angle-independent photon harvesting in organic homo-tandem solar cells

Mertens, Adrian; Mescher, Jan; Bahro, Daniel; Koppitz, Manuel; Colsmann, Alexander

doi:10.1364/oe.24.00a898

Cited by 10 publications

(8 citation statements)

References 28 publications

(31 reference statements)

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“…Nevertheless, in practical scenarios the solar cell is not constantly oriented in such direction but there is rather a certain angle of incidence. Mertens et al tried to understand a peculiar behavior of organic tandem solar cells, already reported by Riede et al for evaporated tandem cells. In detail, when their device was at a certain angle of orientation Θ with respect to the direction of incidence of light, the short‐circuit current density corrected for the effective area of illumination ( J* SC = J SC /cos( Θ )) was relatively insensitive to this angle, up to 65° .…”

Section: Tandem Solar Cellsmentioning

confidence: 99%

“…Mertens et al tried to understand a peculiar behavior of organic tandem solar cells, already reported by Riede et al for evaporated tandem cells. In detail, when their device was at a certain angle of orientation Θ with respect to the direction of incidence of light, the short‐circuit current density corrected for the effective area of illumination ( J* SC = J SC /cos( Θ )) was relatively insensitive to this angle, up to 65° . In their work, the authors showed that both the measured and modeled EQE spectra of the individual subcells change according to Θ .…”

Section: Tandem Solar Cellsmentioning

confidence: 99%

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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%

Section: Tandem Solar Cellsmentioning

confidence: 99%

Advances in Solution‐Processed Multijunction Organic Solar Cells

2018

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“…To efficiently handle the huge parameter space, we performed comprehensive optical device simulations . Based on these simulations Figure a depicts the normalized number of absorbed photons N *( θ )= N /cos( θ ) within the photoactive layer versus the angle θ , depending on the thicknesses of the photoactive layer and the PEDOT:PSS electrode.…”

Section: Resultsmentioning

confidence: 99%

“…To efficiently handle the huge parameter space,w ep erformed comprehensive optical device simulations. [17,18] Based on these simulations Figure 2a depicts the normalized number of absorbed photons N*(q) = N/cos(q)w ithin the photoactive layer versus the angle q,d epending on the thicknesses of the photoactivel ayer andt he PEDOT:PSSe lectrode. N and N*(q)d irectly relate to J sc and J sc *(q)t hrough the internal quantum efficiency,w hich, however, may be dependentont he layer thickness and illumination intensity.F or technical reasonsi nt he subsequent device fabrication, the ITO layer thickness was kept constant.…”

Section: Optical Solar Cell Optimizationmentioning

confidence: 99%

Solar Glasses: A Case Study on Semitransparent Organic Solar Cells for Self‐Powered, Smart, Wearable Devices

et al. 2017

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We report on solution‐processed, semitransparent organic solar cells that are implemented as lenses in sunglasses. The electrical power provided by the lens‐fitted solar cells sustains a microelectronic circuit that is used to read out temperature and illumination intensity sensors and to make this information available on two displays integrated into the temples of the “Solar Glasses”. The microelectronic circuit is designed to operate at illumination intensities down to 500 lux, rendering the Solar Glasses suitable for outdoor and indoor use as well as for operation in diffuse light. Hence, this case study provides an example for consumer‐oriented mobile applications, self‐powered by integrated solar cells, which specifically exploit the unique properties of organic solar cells.

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“…This material is surprisingly used only in a few studies in the literature and never used in an OLED device to our knowledge. [49][50][51] The issue of the poor wetting of an electrode material on top of the emissive area also arises when a hole-injection layer (HIL) material is deposited on top of the emissive area. PEDOT:PSS Al4083 is widely used as a HIL layer in direct devices but it is rather difficult to form a homogeneous layer in an inverted device.…”

Section: Introductionmentioning

confidence: 99%