fig1 shows a schematic view from the side of a seat device 10 according to the invention , which comprises a seat region 30 and a region of a headrest 40 , which is formed at an upper end of the seat device 10 . the seat device 10 comprises a seat frame 50 in the region of its underside , this seat frame being used to connect the seat to an aircraft ( not illustrated ). the seat device 10 comprises an armrest 80 in the region of a transverse end of the seat region 30 , this armrest comprising a passenger control unit ( pcu ) 60 on its surface in the region of its free longitudinal end . the pcu 60 may for example comprise an amplifier for headphones ( not illustrated ) and a control panel with control buttons ( not illustrated ) for an in - flight entertainment system . the pcu 60 is supplied with electrical energy which is generated by a solar cell 20 by means of a power cable 70 . in this case the photoelectric device is formed by the solar cell 20 . the solar cell 20 may extend substantially along the transverse direction of the seat device 10 and is arranged at the upper end of the headrest 40 . the present seat device 10 advantageously enables the pcu 60 to be supplied with energy independently of the on - board network of the aircraft , so that the present seat device 10 does not need to be connected to this network , as would otherwise be the case . the pcu 60 may also comprise a transmitter ( not illustrated ) and a receiver ( not illustrated ). these are used to transmit the control commands received from the pcu 60 , preferably wirelessly , to an associated receiver ( not illustrated ), e . g . the ife system , and for wireless reception of audio signals . fig2 shows a schematic perspective view of a seat device according to a second embodiment of the invention . this embodiment of the seat device 10 according to the invention is substantially identical to the seat device in fig1 with the result that only differences are explained below . the seat device 10 no longer contains a pcu in the region of the armrest 80 , but instead comprises an interface for the power supply 90 for an electrical device ( not illustrated ) in the region of the free longitudinal end of the armrest 80 , this interface being supplied with electrical energy by means of a power cable 70 from the solar cell 20 . the interface for the power supply 90 extends substantially along the thickness direction of the armrest 80 . the interface for the power supply 90 is in particular a usb interface which makes it possible to transmit electrical energy . the electrical device may be a so - called passenger electronic device ( ped ), e . g . an mp3 player or a smartphone , which only requires minimal power consumption for charging purposes . the proposed seat device 10 thus makes it possible to provide an independent power supply for an electrical device with low energy consumption , with the result that it is no longer necessary for this electrical energy to be supplied by the on - board network of the aircraft . fig3 shows a schematic perspective view of a cover 100 according to the invention to be connected to a seat device ( not illustrated ). the cover 100 is in this case formed from a material which does not have any inherent rigidity , with the result that the cover 100 is preferably connected to a portion of the seat device by placing over this portion , the cover 100 then substantially assuming the form of the connection region with the seat device . a photoelectric device 20 is arranged in the region of the upper end of the cover 100 , this device preferably taking the form of a solar cell . the solar cell 20 extends in particular in the longitudinal direction of the cover 100 . the cover 100 also comprises an amplifier 110 in a region of the longitudinal end thereof , this amplifier being supplied via a power cable 70 with electrical energy which is generated by the solar cell 20 and supplied to the amplifier 110 . the amplifier 110 comprises a mechanical interface for connection to headphones ( not illustrated ) such that a passenger can hear the audio signal amplified by the amplifier 110 . in addition , the amplifier 110 may comprise a transmitter / receiver ( not illustrated ) which is designed to send control signals to the ife system or the cabin management system and to receive input signals from the audio channel of the ife system wirelessly , these signals being passed in turn to the amplifier 110 , so that it is advantageously no longer necessary to have a wired connection from the ife system to the amplifier 110 . the cover 100 also comprises a passenger control unit ( pcu ) 60 with a control panel 120 in a region of its longitudinal end opposite the amplifier 110 on the same side , this control panel being supplied with electrical energy which is generated by the solar cell 20 . the pcu 60 is designed to provide control commands for operation of the amplifier 110 , so that in particular the volume of the audio signal amplified by the amplifier 110 can be adjusted by the passenger on the control panel 120 of the pcu 60 . the present cover 100 advantageously permits a wireless solution for audio playback within an ife system ( not illustrated ) due to the pcu 60 being provided with a transmitter connected to the amplifier 110 described above , in which wires are not required to transmit the audio signal to the passenger , nor to supply electrical power to the pcu 60 which is otherwise usually located in the seat . in addition , when using the present cover 100 , it is advantageously no longer necessary to modify the seat , with the result that the cover 100 can easily be retrofitted to existing seats or seat modules for aircraft . although the present invention has been described here by means of preferred embodiments , it is not limited to these embodiments , but rather may be modified in multiple ways . for example , the solar cell 20 may comprise a large number of lenses on its surface with material properties which are selected such that absorption of the wavelength of the incident light which causes energy to be generated in the photoelectric device during operation is minimised .