We have studied the nonlocal photovoltaic response to a laser beam in CdTe/CdS solar cells. The laser-generated plasma is shown to spatially decay over a considerable distance that depends on the device lateral resistance and laser beam power. This affects open circuit voltage far from the laser spot. For the case when the lateral resistance is dominated by the transparent conductive oxide (in completed devices), it is shown that the characteristic decay length may be as long as 1 m. For the alternative case of unfinished devices that do not have a metal layer, the semiconductor layer sheet resistance dominates the nonequilibrium plasma spreading, and the characteristic decay length falls into the range of tenths of a millimeter. Also associated with such nonlocal response are features in photoluminescence mapping, where different excitation powers lead to different map topologies. We have developed a theory that expresses the effects of laser-generated plasma spreading in terms of the semiconductor film photovoltaic parameters.

1.
N.
Nango
,
S.
Iida
, and
T.
Ogawa
,
J. Appl. Phys.
86
,
6000
(
1999
).
2.
Z. F.
Li
,
W.
Lu
,
G. S.
Huang
,
R.
Yang
,
L.
He
,
J. Appl. Phys.
90
,
260
(
2001
).
3.
S. A.
Galloway
,
R. P.
Edwards
, and
K.
Durose
,
Inst. Phys. Conf. Ser.
157
,
579
(
1997
).
4.
R.
Harju
,
V. G.
Karpov
,
D.
Grecu
, and
G.
Dorer
,
J. Appl. Phys.
88
,
1794
(
2000
).
5.
J. F. Hiltner and J. R. Sites, in Proceedings 28th IEEE Photovoltaic Specialists Conference, Alaska, 2000, p. 543.
6.
S. A.
Galloway
,
W. A.
Brinkman
,
K.
Durose
,
P. R.
Wilshaw
, and
A. J.
Holland
,
Appl. Phys. Lett.
68
,
3725
(
1996
).
7.
C. Christopolous, The transmission Line Modeling Methods (IEEE, New York, 1995).
8.
S. M. Sze, Physics of Semiconductor Devices (Wiley, New York, 1981).
9.
V. G.
Karpov
,
G.
Rich
,
A. V.
Subashiev
, and
G.
Dorer
,
J. Appl. Phys.
89
,
4975
(
2001
).
10.
A comment is in order regarding the case of polycrystalline semiconductors in which conductivity is dominated by the intergrain potential barriers. Because of the screening phenomenon, the intergrain barrier height depends on the carrier concentration, hence, on the local electric potential. This, in turn, leads to an exponential dependence ρ(φ), which in the simplest approximation, can be accounted for by renormalizing the parameter α in Eq. (3). As a result, α is considered a phenomenological parameter, whose value can be either less or larger than unity or even negative.
11.
V. G. Karpov, R. Harju, and G. Dorer, in Proceedings 28th IEEE Photovoltaic Specialists Conference, Alaska, 2000, p. 547.
12.
R. H. Bube, Photovoltaic Materials (Imperial College Press, London, 1998).
13.
A. L. Efros and B. I. Shklovskii, Electronic Properties of Doped Semiconductors (Springer, Berlin, 1992).
This content is only available via PDF.
You do not currently have access to this content.