Tutorial: Understanding Solar Photovoltaic Materials

My tutorial talk at the Scanlon Materials Theory Group meeting on understanding solar photovoltaic materials.

See the talk on YouTube here: youtu.be/vuBLQ4mCegA

Transcript

1. Tutorial: Solar Photovoltaics Seán Kavanagh, 14/01/2021
2. What goes in a solar cell?
3. Photovoltaic (PV) Effect E Definition: The generation of voltage and electric current in a material upon exposure to light. PV cells make up >98% of the global solar energy market.1 (1) Bp - Statistical Review of World Energy 2020.
4. Photovoltaic (PV) Effect Wikipedia: The generation of voltage and electric current in a material upon exposure to light. PV cells make up >98% of the global solar energy market.1 (1) Bp - Statistical Review of World Energy 2020.
5. Semiconductor Electronic Structure −6 −4 −2 0 2 4 6 (nergy (eV) ArE. unitV TotDO D26 I (S) 6 (S) 6E (S) 6n (V) 6n (S)
6. Semiconductor Electronic Structure
7. Shockley-Quiesser (SQ) Model How big a gap do we want?
8. Electronic Structure: Nature of the Band Gap  Y C ∣   Z A ∣ ( TY ∣  6 R Z T −6 −4 −2 0 2 4 6 (nergy (eV)
9. Electronic Structure: Nature of the Band Gap  Y C ∣   Z A ∣ ( TY ∣  6 R Z T −6 −4 −2 0 2 4 6 (nergy (eV) Direct Gap Semiconductor: Log(Absorption) Energy E g, Direct
10. Electronic Structure: Nature of the Band Gap Indirect Gap Semiconductor: Log(Absorption) Energy E g, Direct E g, Indirect
11. Fundamental vs Optical
12. Fundamental vs Optical Excitonic Effects: Eg, Fundamental > Eg, Optical
13. Fundamental vs Optical (Symmetry) Forbidden Transitions: Eg, Fundamental < Eg, Optical Walsh, A. et al. Phys. Rev. Lett. 2008, 100 (16), 167402. https://doi.org/10.1103/PhysRevLett.100.167402. For M21 > 0: - ΔSpin = 0 - ΔParity ≠ 0
14. Fundamental vs Optical Spectroscopic Limited Maximal Efficiency (SLME) Yu, L.; Zunger, A. Phys. Rev. Lett. 2012, 108 (6), 068701. https://doi.org/10.1103/PhysRevLett.108.068701. See pymatgen.analysis.solar.slme
15. Solar Cell Operation (y-axis often flipped, depending on convention) Valence Band Conduction Band E g = 1.68 eV Vacuum Level Open-Circuit Voltage? Short-Circuit Current? Fill Factor? Electrical Physics: Power = (Current)(Voltage) P = IV
16. Solar Cell Operation (y-axis often flipped, depending on convention)
17. Features of an Ideal PV Absorber • Efficient (Defects, Exciton Separation, Carrier Mobility…) • Cheap & Abundant Materials • Stable • Non-Toxic • Scalable Fabrication …