Transient Decay Analysis in a-Si by Monte Carlo Method
- PDF / 239,628 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 81 Downloads / 190 Views
TRANSIENT DECAY ANALYSIS IN a-Si BY MONTE CARLO METHOD MANFREDOTTI C.*, A. PAVESE*, F. FIZZOTTIW, U. NASTASI* and G. AMATO0* * Experimental Physics Dept., University of Torino, Via P. Giuria 1, 10125 Torino (Italy) ** Istituto Elettrotecnico Nazionale Galileo Ferraris, Strada delle Cacce, 10100 Torino (Italy) ABSTRACT Both the optical and transport properties of a-Si: H have been suitably parametrized as a function of Urbach's tail logarithmic slope Eo, surface density of states N and optical absorption normalization parameter in order to reduce the number of parameters used for p-i-n solar cell simulation. The transient photovoltaic effect has been simulated by a Monte Carlo multitrapping computer model in order to investigate the possibility of its use for p-i-n solar cell diagnostics. INTRODUCTION
Simulation is important in electronic devices shortens the time needed for prototype realization, impressively long of the number of parameters is optimization by simulation cannot be univocally directed solution,
if
design which large. towards
since it could be But also the best
the number of parameters cannot be strongly reduced to the
most important ones. A similar problem occurs also in pin a-Si:H solar cell design: the number of parameters is extremely large, since all the deposition parameters for the three regions are involved, together with their physical (electrical, optical, transport) properties, interfaces characteristics, optical coatings, electrodes, etc. The approach which has been used in this work is to assume that, firstly, only i-layer is really important and, secondly, that only the optical properties, i.e. those ones determined by optical absorption and PDS should be used. Thirdly, the optical absorption curve is fitted by only two parameters, a , which is used as normalization factor, and Eo, which is the logarithmic slope of Urbach's tail. All the other properties are derived from these two parameters. For transport in the cell, a Monte Carlo program based on multitrapping model has been used. The results are presented only for the transient short circuit photocurrent case. Clearly, this work represents only a very first approach to the problem of parametrization, which should be considered also as a means for searching the existing correlations among the significant physical properties.
Mat. Res. Soc. Symp. Proc. Vol. 118. 91988 Materials Research Society
S
612
THE PARAMETRIZATION OF OPTICAL AND TRANSPORT PROPERTIES Let us assume the following relationship between Eo, the dangling bond density N in the bulk and in the surface N and the mobility lifetime products [1,21. Nb = 8.4xlO13 exp(E /10)
where E is expressed in meV
pT(b) = 6.7x10 11 Nb-107T(s) = 5.61011 N -1.1 b s
(1) (2) (3)
By assuming an exponential decay from surface too bulk density of states and by assuming a surface region thickness d = 200A, one can obtain the following relationship = A [1-B exp (-Kx)]
VW(x)
(4)
where K=5xlO 5 cm 1 , while A and B can be obtained by comparison with Eqs (2) and (3). Finally, from R
Data Loading...
