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Power generating reflective-type liquid crystal displays using a reflective polariser and a polymer solar cell.

Ho Huh Y, Park B - Sci Rep (2015)

Bottom Line: We herein report the results of a study of a power generating reflective-type liquid crystal display (LCD), composed of a 90° twisted nematic (TN) LC cell attached to the top of a light-absorbing polymer solar cell (PSC), i.e., a Solar-LCD.The Solar-LCD also exhibited a significantly improved contrast ratio of more than 17-19.We believe there is a clear case for using such Solar-LCDs in new power-generating reflective-type displays; taken as a whole these results also demonstrate the possibility of their application in a number of energy-harvesting opto-electrical display devices.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrophysics, Kwangwoon Univ., Wolgye-Dong, Nowon-gu, Seoul 139-701, Korea.

ABSTRACT
We herein report the results of a study of a power generating reflective-type liquid crystal display (LCD), composed of a 90° twisted nematic (TN) LC cell attached to the top of a light-absorbing polymer solar cell (PSC), i.e., a Solar-LCD. The PSC consisted of a polymer bulk-heterojunction photovoltaic (PV) layer of poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] and [6,6]-phenyl C71 butyric acid methyl ester (PCDTBT:PCBM70), and showed a high power conversion efficiency of about 5%. In order to improve the visibility of the Solar-LCD, between the TN-LC and the PV cells we inserted a reflective polariser of a giant birefringent optical (GBO) film. The reflectivity from the Solar-LCD was observed to be considerably increased by more than 13-15% under illumination by visible light. The Solar-LCD also exhibited a significantly improved contrast ratio of more than 17-19. We believe there is a clear case for using such Solar-LCDs in new power-generating reflective-type displays; taken as a whole these results also demonstrate the possibility of their application in a number of energy-harvesting opto-electrical display devices.

No MeSH data available.


Schematic illustration of the bright (left) and dark (right) pixels of the reflective-type Solar-LCD, consisting of a front linear dichroic sheet polariser, TN-LC cells, a rear reflective polariser, and a polymer solar cell in the normally white mode.The white arrows indicate the propagation of incident lights and the red arrows (↕) represent the polarisation directions of the propagating lights. The T axis shown indicates the passing axis of the polarisers.
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f1: Schematic illustration of the bright (left) and dark (right) pixels of the reflective-type Solar-LCD, consisting of a front linear dichroic sheet polariser, TN-LC cells, a rear reflective polariser, and a polymer solar cell in the normally white mode.The white arrows indicate the propagation of incident lights and the red arrows (↕) represent the polarisation directions of the propagating lights. The T axis shown indicates the passing axis of the polarisers.

Mentions: Figure 1 shows an exploded schematic illustration of the reflective-type Solar-LCD investigated in this study. The Solar-LCD includes, in order, a bottom light-absorbing isotropic PSC, a rear GBO reflective polariser, top TN-LC cells, and a front or light-exiting dichroic linear sheet polariser. Here, the top TN-LC cells, in which a 90° twisted orientation of the LC molecules is used with cell gap d, birefringence Δn, and electrodes placed between the substrates, may be a light valve or an LCD having a matrix array of pixels and coloured (i.e., RGB) subpixels. Two modes of operation of the Solar-LCD device may be possible, depending on the orientation of the passing axis of the GBO polariser. When the passing axis of the rear GBO polariser is parallel to that of the front polariser (parallel-polariser condition), the device can operate in the NW mode. When no voltage is applied (the “OFF” state, left pixel in TN-LC), after passing through the front dichroic polariser the polarised light enters the TN-LC cell, where the twisted orientation of the LC molecules causes the light to change its polarisation by 90° under the Mauguin condition40 with a retardation value >> 0.5 λ for an incident light of wavelength λ, in waveguide fashion, making it perpendicular to the passing axis of the rear GBO reflecting polariser. The light that emerges from the TN-LC cell is thus blocked and reflected at the GBO polariser, because here its polarisation is perpendicular to the passing axis of the GBO polariser in this bright state. In contrast, when a voltage is applied to the TN-LC cell (the “ON” state, right pixel in the TN-LC), the LC molecules begin to align along the electric field due to the positive dielectric anisotropy of the LC. At a sufficiently high field, the 90° twist is removed, and the polarisation of the light passing through the TN-LC cell does not change. Thus, the light that passes through the TN-LC cell passes through the second reflective polariser, implying that the rectilinearly propagating light is absorbed by the bottom PSC and contributes to the power generation such that the TN-LC cell is observed to be in the black state. The reflected output of the system therefore ranges from the bright reflection state to the dark extinction state, depending on the voltage applied to the TN-LC cell. The grey scale of the reflected output of the system is achieved by applying intermediate voltages between zero and the value at which light is completely transmitted. We also note that if the passing axis of the rear reflective polariser is perpendicular to that of the front polariser (cross-polariser condition), light is then absorbed (dark) at the field-off state and reflected (bright) at the field-on state (the normal black (NB) mode). In addition to its display ability, as mentioned above the light-absorbing bottom (unrubbed) PSC in the Solar-LCD can generate electricity using the selectively absorbed light. This allows our Solar-LCD to be used as a new power-generating reflective-type LC display, in which the entire surface is available for use in the display with a high contrast ratio and a high PV performance, unlike conventional reflective LC displays or conventional rubbed Solar-LCDs.


Power generating reflective-type liquid crystal displays using a reflective polariser and a polymer solar cell.

Ho Huh Y, Park B - Sci Rep (2015)

Schematic illustration of the bright (left) and dark (right) pixels of the reflective-type Solar-LCD, consisting of a front linear dichroic sheet polariser, TN-LC cells, a rear reflective polariser, and a polymer solar cell in the normally white mode.The white arrows indicate the propagation of incident lights and the red arrows (↕) represent the polarisation directions of the propagating lights. The T axis shown indicates the passing axis of the polarisers.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4477406&req=5

f1: Schematic illustration of the bright (left) and dark (right) pixels of the reflective-type Solar-LCD, consisting of a front linear dichroic sheet polariser, TN-LC cells, a rear reflective polariser, and a polymer solar cell in the normally white mode.The white arrows indicate the propagation of incident lights and the red arrows (↕) represent the polarisation directions of the propagating lights. The T axis shown indicates the passing axis of the polarisers.
Mentions: Figure 1 shows an exploded schematic illustration of the reflective-type Solar-LCD investigated in this study. The Solar-LCD includes, in order, a bottom light-absorbing isotropic PSC, a rear GBO reflective polariser, top TN-LC cells, and a front or light-exiting dichroic linear sheet polariser. Here, the top TN-LC cells, in which a 90° twisted orientation of the LC molecules is used with cell gap d, birefringence Δn, and electrodes placed between the substrates, may be a light valve or an LCD having a matrix array of pixels and coloured (i.e., RGB) subpixels. Two modes of operation of the Solar-LCD device may be possible, depending on the orientation of the passing axis of the GBO polariser. When the passing axis of the rear GBO polariser is parallel to that of the front polariser (parallel-polariser condition), the device can operate in the NW mode. When no voltage is applied (the “OFF” state, left pixel in TN-LC), after passing through the front dichroic polariser the polarised light enters the TN-LC cell, where the twisted orientation of the LC molecules causes the light to change its polarisation by 90° under the Mauguin condition40 with a retardation value >> 0.5 λ for an incident light of wavelength λ, in waveguide fashion, making it perpendicular to the passing axis of the rear GBO reflecting polariser. The light that emerges from the TN-LC cell is thus blocked and reflected at the GBO polariser, because here its polarisation is perpendicular to the passing axis of the GBO polariser in this bright state. In contrast, when a voltage is applied to the TN-LC cell (the “ON” state, right pixel in the TN-LC), the LC molecules begin to align along the electric field due to the positive dielectric anisotropy of the LC. At a sufficiently high field, the 90° twist is removed, and the polarisation of the light passing through the TN-LC cell does not change. Thus, the light that passes through the TN-LC cell passes through the second reflective polariser, implying that the rectilinearly propagating light is absorbed by the bottom PSC and contributes to the power generation such that the TN-LC cell is observed to be in the black state. The reflected output of the system therefore ranges from the bright reflection state to the dark extinction state, depending on the voltage applied to the TN-LC cell. The grey scale of the reflected output of the system is achieved by applying intermediate voltages between zero and the value at which light is completely transmitted. We also note that if the passing axis of the rear reflective polariser is perpendicular to that of the front polariser (cross-polariser condition), light is then absorbed (dark) at the field-off state and reflected (bright) at the field-on state (the normal black (NB) mode). In addition to its display ability, as mentioned above the light-absorbing bottom (unrubbed) PSC in the Solar-LCD can generate electricity using the selectively absorbed light. This allows our Solar-LCD to be used as a new power-generating reflective-type LC display, in which the entire surface is available for use in the display with a high contrast ratio and a high PV performance, unlike conventional reflective LC displays or conventional rubbed Solar-LCDs.

Bottom Line: We herein report the results of a study of a power generating reflective-type liquid crystal display (LCD), composed of a 90° twisted nematic (TN) LC cell attached to the top of a light-absorbing polymer solar cell (PSC), i.e., a Solar-LCD.The Solar-LCD also exhibited a significantly improved contrast ratio of more than 17-19.We believe there is a clear case for using such Solar-LCDs in new power-generating reflective-type displays; taken as a whole these results also demonstrate the possibility of their application in a number of energy-harvesting opto-electrical display devices.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrophysics, Kwangwoon Univ., Wolgye-Dong, Nowon-gu, Seoul 139-701, Korea.

ABSTRACT
We herein report the results of a study of a power generating reflective-type liquid crystal display (LCD), composed of a 90° twisted nematic (TN) LC cell attached to the top of a light-absorbing polymer solar cell (PSC), i.e., a Solar-LCD. The PSC consisted of a polymer bulk-heterojunction photovoltaic (PV) layer of poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] and [6,6]-phenyl C71 butyric acid methyl ester (PCDTBT:PCBM70), and showed a high power conversion efficiency of about 5%. In order to improve the visibility of the Solar-LCD, between the TN-LC and the PV cells we inserted a reflective polariser of a giant birefringent optical (GBO) film. The reflectivity from the Solar-LCD was observed to be considerably increased by more than 13-15% under illumination by visible light. The Solar-LCD also exhibited a significantly improved contrast ratio of more than 17-19. We believe there is a clear case for using such Solar-LCDs in new power-generating reflective-type displays; taken as a whole these results also demonstrate the possibility of their application in a number of energy-harvesting opto-electrical display devices.

No MeSH data available.