refer to articles where also other dye combinations for achieving important FRET
functionalities have been discussed [14, 15, 46, 181, 207].
Out of the many possible applications of such ZL-based FRET-composites that
have been discussed in the literature, we refer only to utilization in luminescent solar
concentrators (LSC). A LSC is a wave-guiding plate containing luminescent chromophores [208, 209]. Light enters the face of the plate, is absorbed, and is subsequently emitted at longer wavelength. The luminescent light is trapped by total
internal reflection and guided to the edges of the plate, where it can be converted to
electricity by a photovoltaic cell. Because the edge area of the plate is much smaller
than the face area, the LSC operates as a concentrator of light. It has been well
understood for more than 30 years that a major reflection loss in such a device is
caused by the overlap between the absorption and emission spectra of the chromophores [208–214]. A way to minimize this loss is to use specific antenna material as
illustrated in Fig. 28 [16]. Absorption and emission spectra are separated by
employing a large amount of a strongly absorbing dye and very little emitting dye.
This system bears important properties needed for an LSC. An important prerequisite is that light scattering can be suppressed quantitatively in the region of emission,
because even weak scattering results in very severe losses. This criterion seems so
far to be only partially fulfilled by ZL-based composites, despite of remarkable
progress that has been made [16, 99, 103, 110, 215]. The emitting HR used in the
composite shown in Fig. 28 cannot be considered as ideal, as already discussed in
[16]. More research, and advanced chemical engineering, is needed for finding an
optimal emitting dye. It seems also necessary to study the influence of the co-guest
regarding the long-time stability of the material in order to meet the hard conditions
faced in outdoor application. Monolayers of oriented ZL-based composites, as
reported in Fig. 12, can be used to prepare optically strongly anisotropic layers,
thus reducing reflection losses considerably [15]. This option is waiting to be
explored. The wavelength range that has been covered so far by ZL-based antenna
composites extends from the near UV to about 700 nm. Extension to 850 nm or even
900 nm looks possible but remains challenging. It seems that the materials known
are not far away from being ready for realizing stable and efficient LSC devices. The
research and technological effort needed for arriving there should, nevertheless, not
be underestimated.
9.1 Communication with the Outside World
The stopcocks reported in Table 4 can be used for sealing the nanochannels of ZL
crystals partially or completely regarding matter exchange with the environment.
They can be used for binding individual crystals into chains or to arrange crystals
perpendicularly to a surface, thus forming dense monolayers of oriented crystals.
The stopcock-driven self-assembling of ZL crystals into uniformly oriented layers
can be extended using cooperative interaction of a ligand function reacting with
metal cations [76]. Some of the stopcocks in Table 4 consist of a part which can be
56
G. Calzaferri
functionalities have been discussed [14, 15, 46, 181, 207].
Out of the many possible applications of such ZL-based FRET-composites that
have been discussed in the literature, we refer only to utilization in luminescent solar
concentrators (LSC). A LSC is a wave-guiding plate containing luminescent chromophores [208, 209]. Light enters the face of the plate, is absorbed, and is subsequently emitted at longer wavelength. The luminescent light is trapped by total
internal reflection and guided to the edges of the plate, where it can be converted to
electricity by a photovoltaic cell. Because the edge area of the plate is much smaller
than the face area, the LSC operates as a concentrator of light. It has been well
understood for more than 30 years that a major reflection loss in such a device is
caused by the overlap between the absorption and emission spectra of the chromophores [208–214]. A way to minimize this loss is to use specific antenna material as
illustrated in Fig. 28 [16]. Absorption and emission spectra are separated by
employing a large amount of a strongly absorbing dye and very little emitting dye.
This system bears important properties needed for an LSC. An important prerequisite is that light scattering can be suppressed quantitatively in the region of emission,
because even weak scattering results in very severe losses. This criterion seems so
far to be only partially fulfilled by ZL-based composites, despite of remarkable
progress that has been made [16, 99, 103, 110, 215]. The emitting HR used in the
composite shown in Fig. 28 cannot be considered as ideal, as already discussed in
[16]. More research, and advanced chemical engineering, is needed for finding an
optimal emitting dye. It seems also necessary to study the influence of the co-guest
regarding the long-time stability of the material in order to meet the hard conditions
faced in outdoor application. Monolayers of oriented ZL-based composites, as
reported in Fig. 12, can be used to prepare optically strongly anisotropic layers,
thus reducing reflection losses considerably [15]. This option is waiting to be
explored. The wavelength range that has been covered so far by ZL-based antenna
composites extends from the near UV to about 700 nm. Extension to 850 nm or even
900 nm looks possible but remains challenging. It seems that the materials known
are not far away from being ready for realizing stable and efficient LSC devices. The
research and technological effort needed for arriving there should, nevertheless, not
be underestimated.
9.1 Communication with the Outside World
The stopcocks reported in Table 4 can be used for sealing the nanochannels of ZL
crystals partially or completely regarding matter exchange with the environment.
They can be used for binding individual crystals into chains or to arrange crystals
perpendicularly to a surface, thus forming dense monolayers of oriented crystals.
The stopcock-driven self-assembling of ZL crystals into uniformly oriented layers
can be extended using cooperative interaction of a ligand function reacting with
metal cations [76]. Some of the stopcocks in Table 4 consist of a part which can be
56
G. Calzaferri