1. The Green River Organic Photovoltaic Project Werner Heisenberg Nobel Prize Lecture 1933

2. The Green River Organic Photovoltaic Project Light meets matter From atomic spectra to photovoltaic cells. Keith Clay, Green River Community College

3. The Green River Organic Photovoltaic Project Famous inventions We are interested in… Photovoltaic devices produce electricity from light.

4. The Green River Organic Photovoltaic Project Famous inventions We are interested in… Photovoltaic devices produce electricity from light. What does exactly the opposite?

5. The Green River Organic Photovoltaic Project Famous inventions We are interested in… Photovoltaic devices produce electricity from light. What does exactly the opposite?

6. The Green River Organic Photovoltaic Project Famous inventions We are interested in… Photovoltaic devices produce electricity from light. What does exactly the opposite?

7. The Green River Organic Photovoltaic Project About light bulbs CFLs use 20% to 30% as much power. They contain mercury… but so does coal. Incandescent or “traditional” Compact fluorescent or “CFL” How do they work?

8. The Green River Organic Photovoltaic Project About light bulbs Scientists learn about light sources by studying the kinds of “light” they produce. This is called looking at the “spectrum” of the light source.

9. The Green River Organic Photovoltaic Project About light bulbs We can view the visible spectrum with prisms

10. The Green River Organic Photovoltaic Project About light bulbs We can study the spectrum with diffraction gratings

11. The Green River Organic Photovoltaic Project About light bulbs

12. The Green River Organic Photovoltaic Project About light bulbs

13. The Green River Organic Photovoltaic Project About light bulbs

14. The Green River Organic Photovoltaic Project About light bulbs

15. The Green River Organic Photovoltaic Project Quantum Mechanics Werner Heisenberg Nobel Prize Lecture 1933

16. The Green River Organic Photovoltaic Project Quantum Mechanics Werner Heisenberg 1933

17. The Green River Organic Photovoltaic Project Quantum Mechanics Neils Bohr 1913

18. The Green River Organic Photovoltaic Project Quantum Mechanics The Bohr Model of the Atom Hydrogen A proton An electron

19. The Green River Organic Photovoltaic Project Quantum Mechanics The Bohr Model of the Atom

20. The Green River Organic Photovoltaic Project Quantum Mechanics The Bohr Model of the Atom

21. The Green River Organic Photovoltaic Project Quantum Mechanics An atomic system is capable of assuming only discrete states.

22. The Green River Organic Photovoltaic Project Quantum Mechanics An atomic system is capable of assuming only discrete states. This is allowed This is not

23. The Green River Organic Photovoltaic Project Quantum Mechanics Quantum states

24. The Green River Organic Photovoltaic Project Quantum Mechanics Quantum states

25. The Green River Organic Photovoltaic Project Quantum Mechanics Discrete Energy Levels

26. The Green River Organic Photovoltaic Project Quantum Mechanics

27. The Green River Organic Photovoltaic Project Quantum Mechanics Neils Bohr 1913

28. The Green River Organic Photovoltaic Project Quantum Mechanics

29. The Green River Organic Photovoltaic Project Quantum Mechanics photon

30. The Green River Organic Photovoltaic Project Quantum Mechanics

31. The Green River Organic Photovoltaic Project Quantum Mechanics photon

32. The Green River Organic Photovoltaic Project Quantum Mechanics Bohr Atom 1913 Quantum Mechanics a century later

33. The Green River Organic Photovoltaic Project Quantum Mechanics Quantum Mechanics a century later An atomic system is capable of assuming only discrete states.

34. The Green River Organic Photovoltaic Project Quantum Mechanics photon

35. The Green River Organic Photovoltaic Project Quantum Mechanics

36. The Green River Organic Photovoltaic Project Quantum Mechanics Run electric current through hydrogen gas

37. The Green River Organic Photovoltaic Project Quantum Mechanics Atomic spectrum of hydrogen

38. The Green River Organic Photovoltaic Project Quantum Mechanics 434 nm486 nm656 nm Atomic spectrum of hydrogen

39. The Green River Organic Photovoltaic Project Quantum Mechanics photon

40. The Green River Organic Photovoltaic Project Quantum Mechanics photon

41. The Green River Organic Photovoltaic Project Quantum Mechanics 434 nm486 nm656 nm n = 3 to n = 2 Atomic spectrum of hydrogen

42. The Green River Organic Photovoltaic Project Quantum Mechanics 434 nm486 nm656 nm n = 3 to n = 2n = 4 to n = 2n = 5 to n = 2 Atomic spectrum of hydrogen

43. The Green River Organic Photovoltaic Project Atomic Spectra A strange looking light bulb. How does it work?

44. The Green River Organic Photovoltaic Project Atomic Spectra

45. The Green River Organic Photovoltaic Project Atomic Spectra Atomic spectrum of neon

46. The Green River Organic Photovoltaic Project Atomic Spectra How does a fluorescent light bulb work?

47. The Green River Organic Photovoltaic Project Atomic Spectra Atomic spectrum of mercury:

48. The Green River Organic Photovoltaic Project Atomic Spectra Atomic spectrum of mercury: Visible spectrum of CFL: mercuryphosphors

49. The Green River Organic Photovoltaic Project Atomic Spectra mercuryphosphors All five colors blended together

50. The Green River Organic Photovoltaic Project Atomic Spectra An electrified gas through rainbow glasses Atomic spectrum of helium

51. The Green River Organic Photovoltaic Project Atomic Spectra helium hydrogen neon carbon iron

52. The Green River Organic Photovoltaic Project Atomic Spectra

53. The Green River Organic Photovoltaic Project Atomic Spectra Molecular Carbon dioxide

54. The Green River Organic Photovoltaic Project Atomic Spectra Molecular Water

55. The Green River Organic Photovoltaic Project Energy diagrams

56. The Green River Organic Photovoltaic Project Energy diagrams

57. The Green River Organic Photovoltaic Project Energy diagrams Energy states of the hydrogen atom Increasing energy  Increasing angular momentum 

58. The Green River Organic Photovoltaic Project Energy diagrams = 400 nm = 550 nm = 700 nm E = 3.1 eV E = 2.3 eV E = 1.8 eV E = 3.6 eV = 340 nm = 230 nm E = 5.4 eV Cast of characters: The photons Simplified

59. The Green River Organic Photovoltaic Project Energy diagrams Energy states of a simplified system E = 0.0 eV(“Ground state”) E = 5.4 eV E = 2.3 eV E = 1.8 eV Each orbital can hold two electrons = an electron = another electron = a pair of electrons Simplified

60. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system E = 5.4 eV = 230 nm UV photon E = 0.0 eV E = 5.4 eV E = 2.3 eV E = 1.8 eV Shine a UV light on our system

61. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system E = 5.4 eV = 230 nm UV photon E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV

62. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system E = 5.4 eV = 230 nm UV photon E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV

63. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system = an “electron hole” Electron holes Have positive charge Have mass Move through materials much as electrons do E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV

64. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system What happens next? Possibility #1: E = 5.4 eV = 230 nm E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV

65. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system What happens next? Possibility #1: E = 5.4 eV = 230 nm E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV

66. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system What happens next? Possibility #1: E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV “Nothing happened”

67. The Green River Organic Photovoltaic Project Light meets matter What happens next? REFLECTION: Absorption and re-emission of the same type of photon.

68. The Green River Organic Photovoltaic Project Light meets matter What happens next? REFLECTION: Absorption and re-emission of the same type of photon.

69. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system What happens next? Possibility #2: E = 3.6 eV = 340 nm E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV

70. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system What happens next? Possibility #2: E = 1.8 eV = 700 nm E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV

71. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system What happens next? Possibility #2: = 700 nm Light absorbed = 230 nm Light emitted = 340 nm E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV

72. The Green River Organic Photovoltaic Project Light meets matter What happens next? Possibility #1: = 700 nm Light absorbed = 230 nm Light emitted = 340 nm Invisible Visible

73. The Green River Organic Photovoltaic Project Light meets matter What happens next? FLUORESCENCE: Absorption of UV light and immediate emission of visible light. Fluorescence ends when the light source is removed.

74. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system What happens next? Possibility #3: E = 3.1 eV = 400 nm E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV

75. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system What happens next? Possibility #3: E = 2.3 eV = 550 nm E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV Unlikely? Slow?

76. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system What happens next? Possibility #3: E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV = 550 nm Light absorbed = 230 nm Light emitted = 400 nm Immediate Delayed

77. The Green River Organic Photovoltaic Project Light meets matter What happens next? Possibility #3: = 550 nm Light absorbed = 230 nm Light emitted = 400 nm Invisible Visible Immediate Fluorescence Visible Delayed Phosphorescence

78. The Green River Organic Photovoltaic Project Light meets matter What happens next? Phosphorescence: Delayed emission of visible light after absorption of UV light. Phosphorescence continues after the UV energy source is removed. CFL bulbs glow after they are turned off!

79. The Green River Organic Photovoltaic Project Light meets matter Energy states of a simplified system E = 0.0 eV E = 5.4 eV E = 2.3 eV E = 1.8 eV Three processes: 1)Reflection

80. The Green River Organic Photovoltaic Project Light meets matter Three processes: 1)Reflection 2)Fluorescence Energy states of a simplified system E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV

81. The Green River Organic Photovoltaic Project Light meets matter Three processes: 1)Reflection 2)Fluorescence 3)Phosphorescence Energy states of a simplified system E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV

82. The Green River Organic Photovoltaic Project Light meets matter Three processes: 1)Reflection 2)Fluorescence 3)Phosphorescence Energy states of a simplified system E = 2.3 eV E = 1.8 eV E = 5.4 eV E = 0.0 eV All processes happen at once in different atoms

83. The Green River Organic Photovoltaic Project Photovoltaic cells All processes happen at once in different atoms To make a photovoltaic cell: Add another process… that forces the electron to move… so we can capture the energy of the absorbed photon.

84. The Green River Organic Photovoltaic Project Photovoltaic cells To make a photovoltaic cell: Add another process… that forces the electron to move… so we can capture the energy of the absorbed photon.

85. The Green River Organic Photovoltaic Project Photovoltaic cells To make a photovoltaic cell: Add another process… that forces the electron to move… so we can capture the energy of the absorbed photon. Cathode Anode Donor Acceptor Junction

86. The Green River Organic Photovoltaic Project Photovoltaic cells Photon: excites an electron in the donor. Donor: gives up the electron to the acceptor. Acceptor: accepts the electron from the donor. Anode: electrons flow OUT of the anode. Cathode: electrons flow INTO the cathode. Junction: the surface between donor and acceptor Cathode Anode Donor Acceptor Junction

87. The Green River Organic Photovoltaic Project Cathode Anode Donor Acceptor Junction DonorAcceptor Energy levels Electron = Hole = or Cathode Anode Photovoltaic cells “Highest Occupied Molecular Orbitals”

88. The Green River Organic Photovoltaic Project Cathode Anode Donor Acceptor Junction DonorAcceptor Energy levels Electron = Hole = or Cathode Anode Photovoltaic cells “Lowest Unoccupied Molecular Orbitals”

89. The Green River Organic Photovoltaic Project Sunlight Cathode Anode Donor Acceptor Junction DonorAcceptor Energy levels Electron = Hole = or Cathode Anode Photovoltaic cells

90. The Green River Organic Photovoltaic Project Energy levels - + Cathode Anode Donor Acceptor Junction DonorAcceptor Electron = Hole = or Cathode Photovoltaic cells Anode

91. The Green River Organic Photovoltaic Project Energy levels - + Cathode Anode Donor Acceptor Junction DonorAcceptor Electron = Hole = or Cathode Photovoltaic cells Anode

92. The Green River Organic Photovoltaic Project Cathode Anode Donor Acceptor Junction Energy levels DonorAcceptor Electron = Hole = or - + Cathode Anode Photovoltaic cells

93. The Green River Organic Photovoltaic Project Cathode Anode Donor Acceptor Junction Energy levels DonorAcceptor Electron = Hole = or - + Cathode Anode Photovoltaic cells

94. The Green River Organic Photovoltaic Project Cathode Anode Donor Acceptor Junction Energy levels DonorAcceptor Electron = Hole = or - + Cathode Anode Photovoltaic cells

95. The Green River Organic Photovoltaic Project Cathode Anode Donor Acceptor Junction Energy levels DonorAcceptor Electron = Hole = or - Cathode Anode Photovoltaic cells +

96. The Green River Organic Photovoltaic Project Cathode Anode Donor Acceptor Junction Energy levels DonorAcceptor Electron = Hole = or - + Cathode Anode Photovoltaic cells

97. The Green River Organic Photovoltaic Project Cathode Anode Donor Acceptor Junction Energy levels DonorAcceptor Cathode Anode - Photovoltaic cells +

98. The Green River Organic Photovoltaic Project Cathode Anode Donor Acceptor Junction Energy levels DonorAcceptor Cathode Anode - Photovoltaic cells +

99. The Green River Organic Photovoltaic Project Cathode Anode Donor Acceptor Junction Energy levels DonorAcceptor Cathode Anode Photovoltaic cells wire + -

100. The Green River Organic Photovoltaic Project DonorAcceptor Cathode Anode Photovoltaic cells wire

101. The Green River Organic Photovoltaic Project Photovoltaic cells Electricity flows in. Quantum states are excited. Light comes out. Light goes in. Quantum states are excited. Electricity comes out.

102. The Green River Organic Photovoltaic Project Photoelectric megawatts

103. The Green River Organic Photovoltaic Project Photoelectric megawatts All unattributed images are created by the author or borrowed from the Wikimedia Foundation for educational uses only. The author supports the Wikimedia Foundation and encourages viewers to do the same.