Baran Group Meeting
Terry Lou
Solar cell - aka photovoltaic (PV) cell
Dye-Sensitized Solar Cells
Convert light energy into electricity (vs solar collector - thermal)
"Solar PV development will continue to break records, with annual additions
reaching 162 GW by 2022 – almost 50% higher than the pre-pandemic level
of 2019" (IEA, 2020)
Primary energy supply rate = 18.55 TW (2017);
-
Electric power generation = 2.92 TW (2017);
-
Solar PV power = 0.4 TW (2017)
c.f. Solar power reaches the Earth surface = 89,000 TW (1.36 kW/m²)
Exponential Growth of Solar PV (in GW)
1,000
gigawatts
100
2017: 404 GW
10
1
2018: 508 GW (tent.)
Traditional PV cell
Working principle:
Baran Group Meeting
Jun 5, 2021
Absorption of light generates e-/h+ pair at p-n junction
Separation of charge carriers (e- towards n-type; h* towards p-type)
Injection of carriers into external circuit
1st generation crystalline silicon (c-Si)
Monocrystalline (mono-Si)
highest single-cell efficiency n = 26.7%
Multicrystalline (multi-Si): n = 23.3%
2nd generation thin-film solar cells
electrode(minus)
Light
surface
reflective coating
electrode(plus)/
n-type
semiconductor
p-type
semiconductor
underside
reflective coating
Amorphous Si (a-Si), Cadmium telluride (CdTe), Copper indium gallium
selenide (CIGS)
Flexible and low cost; lower efficiency in general (n = 15-20%)
Semiconductor
MIZIRANAW
0
1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018
3rd generation - tandem cells
-
p-type (“positive”) doped with trivalent atoms (B, Ga, In)
-
n-type ("negative") doped with pentavalent atoms (P, As)
-
Fermi level (EF): energy required to add one electron to the body
→ hypothetical energy level of e-
Conduction band - LUMO
-
-
Band gap HOMO-LUMO gap
Valence band - HOMO
EF-
B D D D D
DDD
Metal Semimetal
p-type intrin. n-type
Semiconductor
Insulator
Multi-junction solar cells; best n = 47.1% (4-junction)
Dye-sensitized (DSSC), organic (OSC), and perovskite solar cells (PSC)
Overcome theoretical efficiency limit of 33.7%
Monocrystalline
Polycrystalline
Global Market Share by PV Technology
from 1990 to 2013
100% T
100%
Amorphous
Thin-film
ribbon-Si
75% -
50%
25%-
mono-Si
75%
multi-Si
50%
0%
1990
2000
2010
25%
0%
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