An efficient interconnection unit composed of electron-transporting layer/metal/p-doped hole-transporting layer for tandem organic photovoltaics

Applied Physics Letters

Moon

et al. 2014

Self Cite

We report a high performance green color selective semitransparent inverted organic photodetectors (OPDs) with a detectivity of 2.1 × 1012 cm Hz1/2/W at the wavelength of 530 nm which has the comparable performance to the reported metal electrode based OPDs due to low dark current density of 3.8 × 10−10 A/cm2 at −1 V. The transparent OPD showed high transparency of 26% and 60% in the blue and red regions, respectively. The relatively low transmittance in the blue region can be improved using appropriate selection of active materials which absorb only the green region.

supporting

confidence: 71%

A high performance semitransparent organic photodetector with green color selectivity

Applied Physics Letters

Moon

et al. 2014

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“…The transfer matrix method was used to understand the variation of the J SC value of the ternary devices with variations in the composition and thickness of the active layer. 31,32 The refractive indices of ternary films with different compositions were obtained using a linear combination of binary films, as shown in Figure 3a. The absorbance spectra of films with different compositions calculated using the transfer matrix method and the refractive indices match the experimental ones in Figure S7 well, verifying that the linear combination works well in this system.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Efficient Vacuum-Deposited Ternary Organic Solar Cells with Broad Absorption, Energy Transfer, and Enhanced Hole Mobility

Moon

ACS Appl. Mater. Interfaces

Wang

et al. 2016

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The use of multiple donors in an active layer is an effective way to boost the efficiency of organic solar cells by broadening their absorption window. Here, we report an efficient vacuum-deposited ternary organic photovoltaic (OPV) using two donors, 2-((2-(5-(4-(diphenylamino)phenyl)thieno[3,2-b]thiophen-2-yl)thiazol-5-yl)methylene)malononitrile (DTTz) for visible absorption and 2-((7-(5-(dip-tolylamino)thiophen-2-yl)benzo[c]-[1,2,5]thiadiazol-4-yl)methylene)malononitrile (DTDCTB) for near-infrared absorption, codeposited with C70 in the ternary layer. The ternary device achieved a power conversion efficiency of 8.02%, which is 23% higher than that of binary OPVs. This enhancement is the result of incorporating two donors with complementary absorption covering wavelengths of 350 to 900 nm with higher hole mobility in the ternary layer than that of binary layers consisting of one donor and C70, combined with energy transfer from the donor with lower hole mobility (DTTz) to that with higher mobility (DTDCTB). This structure fulfills all the requirements for efficient ternary OPVs.

“…The ICU is one of the most important components for the design of TOPVs to maximize the performance of the consisting subcells. A previously reported ICU consisting of ETL/metal/p‐HTL is used to connect the subcells because this structure fulfils all the requirements of optical transparency, minimized voltage losses, and working as an optical spacer to match the current between the subcells . In this work, BCP (3 nm) was used as the ETL, Ag (0.5 nm) as the metal, and TAPC:MoO 3 as the p‐HTL, respectively, in the ICU.…”

Section: Resultsmentioning

confidence: 99%

Efficient Vacuum‐Deposited Tandem Organic Solar Cells with Fill Factors Higher Than Single‐Junction Subcells

Lin

Advanced Energy Materials

Sim

et al. 2015

Self Cite

which can only partially response to the solar spectrum, resulting in large optical losses. [6][7][8] To overcome this limitation, ternary blend and tandem structures have been used. The ternary blend OPVs have two donors or acceptors possessing different absorption ranges in the active layers. [ 9,10 ] In contrast, the tandem structures are formed using two or more active layers with different donor-acceptor pairs possessing complementary absorption spectra. Both concepts broaden the absorption range of the solar spectrum, thus to improve the light-harvesting ability of the device. [11][12][13] In tandem structures, however, open-circuit voltage ( V OC ) can be enhanced additionally if the subcells are connected in series. Based on this idea, the PCEs of tandem organic photovoltaic cells (TOPVs) have been enhanced up to ≈10.7% for the solution-processed devices using polymers and ≈10% for the vacuumdeposited devices using small molecules as active materials. [14][15][16][17] The vacuum deposition has several advantages over solution processes for the fabrication of TOPVs such as the possibility of purifying materials via sublimation, no use of solvents, which might damage the predeposited layer, and the capability to precisely control the thickness of respective layers in nanometer scale. Despite these advantages, most vacuum-deposited OPVs still show lower effi ciency than those of solution-processed OPVs. The solution-processed OPVs can be benefi ted from solvent additives and/or post-treatments such as solvent or thermal annealing to assist the formation of ideal nanostructures within the active layer for the better exciton separation and charge transportation. While vacuum-deposited OPVs are confronted by the diffi culty in forming effi cient charge transporting paths in blended active layers due to the limitation of the vacuum fabrication process, thus resulting in lower short-circuit current density ( J SC ) and fi ll factor (FF). [18][19][20] The thickness of the active layer in solution-processed polymer solar cells can be increased up to ≈300 nm without the signifi cant reduction of FF. [ 21 ] High FF of 0.66 was also demonstrated with a 400 nm thick donor layer in a vacuum-processed planar heterojunction OPV where the donor and acceptor layers are separated. [ 22 ] However, the FF in the vacuum-deposited OPVs with mixed active layers decreases rapidly with increasing the active layer thickness. [ 19,23,24 ] Therefore, the thickness of the active layer in Effi cient vacuum-deposited tandem organic photovoltaic cells (TOPVs) composed of pristine fullerenes as the acceptors and two complementary absorbing donors, 2-((2-(5-(4-(diphenylamino)phenyl)thieno[3,2-b] thiophen-2-yl)thiazol-5-yl)methylene)malononitrile for the visible absorption and 2-((7-(5-(dip-tolylamino)thiophen-2-yl)benzo[c]-[1,2,5]thiadiazol-4-yl) methylene)malononitrile for the near-infrared absorption, are reported. Two subcells are connected by the interconnection unit (ICU) composed of electron-transporting layer/metal/p-doped hole-trans...