High volume method of making low-cost, lightweight solar materials
A thin film solar cell and a method fabricating thin film solar cells on flexible substrates. The method includes including providing a flexible polymeric substrate, depositing a photovoltaic precursor on a surface of the substrate, such as CdTe, ZrTe, CdZnTe, CdSe or Cu(In,Ga)Se 2 , and exposing the photovoltaic precursor to at least one 0.5 microsecond to 10 second pulse of predominately infrared light emitted from a light source having a power output of about 20,000 W/cm 2 or less to thermally convert the precursor into a crystalline photovoltaic material having a photovoltaic efficiency of greater than one percent, the conversion being carried out without substantial damage to the substrate.
1. A method of manufacturing a photovoltaic device comprising the steps of:
providing a polymeric substrate including an upper operating temperature, the polymeric substrate being selected from the group consisting of polyamide and polycarbonate;
applying an electrode layer over the polymeric substrate, the electrode layer being applied in roll-to-roll processing and including a material selected from the group consisting of Mo, Ta, W, Ti, ZnO, and ITO;
depositing an amorphous photovoltaic precursor directly or indirectly over the polymeric substrate and the electrode layer, the amorphous photovoltaic precursor including a photovoltaic efficiency of less than 1% and being selected from the group consisting of CdTe, CdS, CdSe, ZnTe, ZrTe, ZnSe, ZnS, CdZnTe, CuInTe 2 and Cu(In,Ga)Se 2 ; and
exposing the photovoltaic precursor to at least one pulse of predominately infrared light from a source of pulsed infrared light to thermally convert the photovoltaic precursor, at an annealing temperature that exceeds the upper operating temperature of the polymeric substrate, into a crystalline photovoltaic material having a photovoltaic efficiency of greater than 1% without causing the polymeric substrate to exceed the substrate upper operating temperature of the polymeric substrate, wherein the polymeric substrate forms a roll-formed web moveable with respect to the source of pulsed infrared light.
2. The method according to claim 1 wherein depositing the photovoltaic precursor includes at least one of screen printing, sputter deposition, solution deposition, vapor deposition, and cold spraying.
3. The method according to claim 1 wherein the source of pulsed infrared light includes a power output of about 20,000 W/cm 2 .
4. The method according to claim 1 , wherein the thermally converted precursor includes a photovoltaic efficiency of greater than 5%.
5. The method according to claim 1 , wherein the pulse includes a pulse duration of between 10 microseconds and 100 milliseconds.
6. The method according to claim 1 , wherein the temperature of the substrate remains below 200° C. during the exposing step.
7. The method according to claim 1 wherein the polymeric substrate is flexible at room temperature.
8. The method according to claim 7 wherein the roll-formed web is operable to move at least one of continuously and step-wise with respect to the stationary source of pulsed infrared light.
9. A method of fabricating a solar cell comprising the steps of:
providing a continuous web including a polymeric substrate selected from the group consisting of polyamide and polycarbonate, the polymeric substrate being flexible at room temperature and defining an upper operating temperature of less than 400° C.;
positioning an electrode layer over the polymeric substrate, the electrode layer being drawn from a roll including a material selected from the group consisting of Mo, Ta, W, Ti, ZnO, and ITO;
depositing an amorphous photovoltaic precursor over the polymeric substrate and over the electrode layer while substantially at room temperature, the amorphous photovoltaic precursor including a photovoltaic efficiency of less than 1% and being selected from the group consisting of CdTe, CdS, CdSe, ZnTe, ZrTe, ZnSe, ZnS, CdZnTe, CuInTe 2 and Cu(In,Ga)Se 2 ; and
annealing the amorphous photovoltaic precursor while in situ over the flexible polymeric substrate and over the electrode layer with exposure to at least one pulse of predominately infrared light directed to an upper superficial region of the photovoltaic precursor, wherein the photovoltaic precursor achieves an annealing temperature that exceeds the upper operating temperature of the polymeric substrate, and wherein the photovoltaic efficiency of the photovoltaic precursor increases from less than 1% to greater than 5% while the temperature of polymeric substrate remains below 200° C.
10. The method according to claim 9 further including spooling the solar cell after annealing the photovoltaic precursor.
11. The method according to claim 9 wherein depositing the photovoltaic precursor over the polymeric substrate and over the electrode layer while substantially at room temperature includes solution deposition.
12. The method according to claim 9 wherein depositing the photovoltaic precursor over the polymeric substrate and over the electrode layer while substantially at room temperature includes screen printing.
13. The method according to claim 9 wherein depositing the photovoltaic precursor over the polymeric substrate and over the electrode layer while substantially at room temperature includes sputter deposition.
14. The method according to claim 9 wherein depositing the photovoltaic precursor over the polymeric substrate and over the electrode layer while substantially at room temperature includes vapor deposition.
15. The method according to claim 9 wherein depositing the photovoltaic precursor over the polymeric substrate and over the electrode layer while substantially at room temperature includes cold-spraying.