Fabrication of organic solar array for applications in microelectromechanical systems and others
A method of fabricating organic solar arrays for application in DC power supplies for electrostatic microelectromechanical systems (MEMS) devices. A solar array with 20 miniature cells (as small as 1 mm 2 ) interconnected in series is fabricated and characterized. Photolithography is used to isolate individual cells and output contacts of the array, whereas the thermal-vacuum deposition is employed to make the series connections of the array. With 1 mm 2 for single cell and a total device area of 2.2 cm 2 , the organic solar array based on bulk heterojunction structure of π-conjugated polymers and C60 derivative (6,6)-phenyl C61 butyric acid methyl ester produces an open-circuit voltage of 7.8 V and a short-circuit current of 55 μA under simulated air mass (AM) 1.5 illumination with an intensity of 132 mW/cm 2 . The present method can be used in the fabrication of microarrays as small as 0.01 mm 2 . This technology can be used to fabricate a power source that is light-weight and environmentally friendly for small electronic devices, with flexibility and cost-effectiveness.
1. A method of fabricating a miniature organic solar array, comprising the steps of:
patterning indium tin oxide onto a glass substrate;
spin coating positive photoresist onto said glass substrate;
soft baking said glass substrate;
exposing said photoresist to a pattern of UV light using a mask and mask aligner, said mask making contact with said photoresist which is used as a stencil for said UV light;
hard baking said glass substrate
developing said glass substrate;
etching said indium tin oxide in a mixed solution of HCL and HNO 3 ;
cleaning said glass substrate;
placing said glass substrate in an inert environment;
spin coating PEDOT:PSS onto said glass substrate;
spin coating an active layer of P3HT:PCBM;
removing excess P3HT:PCBM;
drying said glass substrate;
using a shadow mask to deposit an Aluminum cathode by Thermal Vapor Deposition, said shadow mask being aligned with said glass substrate and acting as a stencil during deposition;
heating said aluminum with current and in vacuum; and
annealing said solar array.
2. The method of claim 1 , further comprising:
said spin coating of positive photoresist onto said substrate being at 4500 rpm for 45 seconds.
3. The method of claim 1 , further comprising:
said soft baking of said glass substrate lasting for 180 seconds at 90 degrees Celsius.
4. The method of claim 1 , further comprising:
said hard bake lasting for 10 minutes at 135 degrees Celsius.
5. The method of claim 1 , further comprising:
said mixed solution of HCL and HNO 3 being 20% HCL and 7% HNO 3 .
6. The method of claim 1 , further comprising:
said cleaning being sonification in trichloroethylene, acetone, and isopropanol at 50 degrees Celcius for 20 minutes.
7. The method of claim 1 , further comprising:
said inert environment being N 2 .
8. The method of claim 1 , further comprising:
said spin coating of an active layer of P3HT:PCBM being at a rate of 700 rpm for 30 seconds.
9. The method of claim 1 , further comprising:
said drying lasting for a minimum of 3 hours.
10. The method of claim 1 , further comprising:
said shadow mask being stainless steel and fabricated using photolithography and a diluted etching solution.
11. The method of claim 10 , further comprising:
said diluted etching solution being FC 13 .
12. The method of claim 1 , further comprising:
said current being 50 amperes and said vacuum being 10^−7 torr.
13. The method of claim 1 , further comprising:
said annealing lasting for 5 minutes at 110 degrees Celsius.