TECHNICAL FIELD

The present disclosure relates to the field of semiconductor technology, and more specifically, to an improved photovoltaic cell.

BACKGROUND

In recent years, there have been several developments towards the realization of wireless sensors. A particular advantage of wireless sensors includes that they can be operated without providing an electrical connection. More specifically, it is typical that such wireless sensors are capable of recharging their own batteries by using energy, which does not require cables. One such form of energy is solar energy. In particular, several sensors have been developed that can be recharged via a photovoltaic cell carried thereby. The advantage of such sensors is that they can be deployed with no infrastructure other than a radio frequency (RF) connection for exchanging data with the sensor and a light source for providing power. At the same time, a similar photovoltaic cell can be used to provide power to pocket calculators, watches and several other small electronic devices. While mainstream photovoltaic technology research has been devoted to the optimization of photovoltaic cells for outdoor use, little development has been done for optimization of cells for indoor use.

SUMMARY

The present disclosure has been made in light of this and provides a manufacturing method and the corresponding photovoltaic cell optimized for indoor use. Such a cell can be employed to operate a plurality of electronic devices, such as sensors for indoor use. Additionally, the photovoltaic cell can be advantageously realized on top of a flexible substrate, thereby allowing the photovoltaic cell to be applied on shapes that are not necessarily flat. The present disclosure also provides a manufacturing method for a flexible substrate and the resulting flexible substrate. The flexible substrate can be advantageously used in combination with the photovoltaic cell described above, for example, in the realization of a flexible sensor. However, the flexible substrate can also be used independently of the photovoltaic cell.

The present disclosure can relate to a photovoltaic cell comprising an hydrogenated amorphous silicon layer including a n-type doped region and a p-type doped region, the n-type doped region being separated from the p-type doped region by an intrinsic region, and a front transparent electrode connected to the n-type doped region and a rear electrode connected to the p-type doped region. The efficiency can be optimized for indoor lighting values by tuning the value of the H2/SiH4 ratio of the hydrogenated amorphous silicon layer.

This may provide the advantage that efficiency can be increased in a simple manner. Additionally, by tuning the H2/SiH4 ratio, it is possible to limit recombination of the holes within the intrinsic part of the silicon layers, thereby allowing the usage of a n-i-p approach, wherein the light source faces the n side of the cell. Such approach may be further advantageous since the n-type doped side of the cell combines particularly well with transparent electrode materials.

In some embodiments, the ratio can be in a range from 2 to 10, and such as preferably 5. This may provide the advantage that the recombination of holes is kept under control, while the lowering of the open circuit voltage may be reduced or minimized. In some embodiments, the front transparent electrode can have a work function equal to or lower than that of the n-type doped region. In particular, in some embodiments the front transparent electrode can include a transparent conductive oxide (TCO) layer, such as any of ZnO:Al, ITO, ZnO:B, ZnO:Ga, ZnO(B), SnO2:F. This may provide the advantage that the collection of electrons on the front electrode is highly efficient.

In some embodiments, the rear electrode can have a work function equal to or higher than that of the p-type doped region. In particular, in some embodiments, the rear electrode can include molybdenum and/or tungsten. This may provide the advantage that collection of holes on the rear electrode is highly efficient.

In some embodiments, the hydrogenated amorphous silicon layer can have a thickness in the range of 100 nm to 1000 nm, and such as preferably 300 nm. This may provide the advantage that the absorption of the light is increased or maximized with a minimal impact on the device induced by light degradation.

Furthermore, the present embodiments can relate to a manufacturing method for the photovoltaic cell according to any previous embodiment wherein the ratio is achieved by deposition of the hydrogenated amorphous silicon layer with SiH4 set in a range from 2 standard cubic centimeters per minute (sccm) to 200 sccm, such as preferably 40 sccm, and H2 is set in a range from 2 to 200 sccm, such as preferably 200 sccm.

In some embodiments, deposition can be carried out in a temperature range from 150° C. to 250° C., such as preferably 190° C. This provides the advantage that an optimal ratio H2/SiH4 ratio can be achieved for efficient operation with indoor lighting.

Moreover, the present disclosure can relate to a flexible sensor comprising at least one sensing element and the photovoltaic cell according to any previous embodiment. Thanks to the high efficiency of the photovoltaic cell, the sensor can achieve reliable operation in an indoor environment.

