192
S. Leu and D. Sontag
Fig. 7.18 a Temperature profile for manufacturing a typical PERC cell. b Temperature profile
for manufacturing a typical HJT cell. The production of a HJT cell has a production time of
approximately 33 min compared to 60 min for a typical PERC cell. The temperature budget for a
HJT cell is about 4 times lower than the temperature budget for a PERC cell
for standard PERC cells: the latter take 60 min to manufacture. The HJT cell requires
8 process steps, while a standard PERC cell requires 11 process steps.
7.5 Temperature Coefficient of HJT Cells
The temperature coefficient TC of a solar cell is mainly given by the temperature
dependence of the open circuit voltage V oc —which in turn depends on the bandgap
of the cell (see Chap. 3). The temperature coefficient TC of a solar cell depends
strongly on the losses in the cell and consists of three parts [17]:
T C MPP = T C V oc + T C J sc + T C FF
(7.10)
In (7.10) T C V oc is the predominant term and accounts for 80–90% of TC MPP .
Table 7.1 Indicative
overview of the temperature
coefficients (TC) and bifacial
factors for a few different
types of solar cells
Technology TC power @MPP (%/K) Bifacial factor (%)
AL-BSF
−0.4
0
PERC
−0.38
0
PERT
−0.35
76
HJT
−0.3
92