Tuning of Barrier Parameters of n-Type Schottky Junctions in Photovoltaic Co-Deposited Films by Doping
Tuning of the barrier parameters of n-type Schottky junctions formed in photovoltaic co-deposited films consisting of fullerene and $\alpha$-sexithiophene (C 60 :6T) was demonstrated by ppm-level control of cesium carbonate (Cs 2 CO 3 ) doping. Increases in the carrier concentration of electrons alo...
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| Published in | Applied physics express Vol. 6; no. 1; pp. 012301 - 012301-3 |
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| Main Authors | , , , |
| Format | Journal Article |
| Language | English |
| Published |
The Japan Society of Applied Physics
01.01.2013
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| Online Access | Get full text |
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| Summary: | Tuning of the barrier parameters of n-type Schottky junctions formed in photovoltaic co-deposited films consisting of fullerene and $\alpha$-sexithiophene (C 60 :6T) was demonstrated by ppm-level control of cesium carbonate (Cs 2 CO 3 ) doping. Increases in the carrier concentration of electrons along with the overall doping concentration, which was observed by capacitance measurements and which affected cell performance, confirmed that Cs 2 CO 3 acts as a donor dopant for C 60 :6T co-deposited films. The doping efficiency was determined to be around 0.15. |
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| Bibliography: | (a) Structure of Cs 2 CO 3 -doped C 60 :6T cells. (b) Action spectra of the EQE for the short-circuit photocurrent. The black curve shows the absorption spectrum of the cell. (c) $I$--$V$ characteristics. The photo and dark currents are shown by the solid and broken curves, respectively. Simulated solar light (AM 1.5, 100 mW cm -2 ) was irradiated onto the ITO electrode. Curves A, B, and C correspond to Cs 2 CO 3 doping concentrations of 40, 150, and 500 ppm, respectively. The measurements were performed at $10^{-3}$ Pa. (a) Dark $I$--$V$ curve obtained by applying a triangular bias at a scanning speed of 5 V s -1 for a 40 ppm Cs 2 CO 3 -doped cell. (b) Mott--Schottky plots for the doping concentrations of 40 (curve A), 150 (curve B), and 500 (curve C) ppm. The measurements were performed using exactly the same cells as those in Fig. . Dependences of donor concentration ($N_{\text{D}}$) (a), built-in potential ($V_{\text{bi}}$) (b), depletion layer width ($W_{\text{dep}}$) (c), and doping efficiency (d) on the Cs 2 CO 3 doping concentrations in a given volume. The number of doped Cs 2 CO 3 molecules per unit volume is also shown on the upper horizontal axis of (a). Molar ratio, i.e., the ratio of the number of Cs 2 CO 3 molecules to that of the sum of the C 60 and 6T molecules, is also shown on the upper horizontal axis. Energy-band diagrams of the Cs 2 CO 3 -doped C 60 :6T cells based on the obtained barrier parameters. C 60 and 6T are shown by the black and orange curves, respectively. The blue shaded areas indicate the depletion layers. CB and VB denote the conduction band and valence band, respectively. Dependence of value of $E_{\text{F}}$ on the thickness of 500 ppm Cs 2 CO 3 doped C 60 :6T films deposited on ITO. |
| ISSN: | 1882-0778 1882-0786 |
| DOI: | 10.7567/APEX.6.012301 |