Implications of the negative capacitance observed at forward bias in nanocomposite and polycrystalline solar cells.
Four different types of solar cells prepared in different laboratories have been characterized by impedance spectroscopy (IS): thin-film CdS/CdTe devices, an extremely thin absorber (eta) solar cell made with microporous TiO2/In(OH)xSy/PbS/PEDOT, an eta-solar cell of nanowire ZnO/CdSe/CuSCN, and a solid-state dye-sensitized solar cell (DSSC) with Spiro-OMeTAD as the transparent hole conductor. A negative capacitance behavior has been observed in all of them at high forward bias, independent of material type (organic and inorganic), configuration, and geometry of the cells studied. The experiments suggest a universality of the underlying phenomenon giving rise to this effect in a broad range of solar cell devices. An equivalent circuit model is suggested to explain the impedance and capacitance spectra, with an inductive recombination pathway that is activated at forward bias. The deleterious effect of negative capacitance on the device performance is discussed, by comparison of the results obtained for a conventional monocrystalline Si solar cell showing the positive chemical capacitance expected in the ideal IS model of a solar cell.
Mora-Seró
Ivan
I
Departament de Ciències Experimentals, Universitat Jaume I, E-12080 Castelló, Spain. sero@exp.uji.es
Bisquert
Juan
J
Fabregat-Santiago
Francisco
F
Garcia-Belmonte
Germà
G
Zoppi
Guillaume
G
Durose
Ken
K
Proskuryakov
Yuri
Y
Oja
Ilona
I
Belaidi
Abdelhak
A
Dittrich
Thomas
T
Tena-Zaera
Ramón
R
Katty
Abou
A
Lévy-Clément
Claude
C
Barrioz
Vincent
V
Irvine
Stuart J C
SJ
D019187:Cadmium Compounds / Q000737:chemistry* / Q000528:radiation effects; D003198:Computer Simulation; D003460:Crystallization / Q000379:methods; D025802:Electric Capacitance; D011211:Electric Power Supplies; D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008027:Light; D008422:Materials Testing; D008956:Models, Chemical; D049329:Nanostructures / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects; D012993:Solar Energy; D013440:Sulfides / Q000737:chemistry* / Q000528:radiation effects; D013691:Tellurium / Q000737:chemistry* / Q000528:radiation effects
D019187:Cadmium Compounds; D013440:Sulfides; C034939:cadmium sulfide; D013691:Tellurium; C028337:cadmium telluride