HEAVILY DOPED TRANSPARENT-EMITTER REGIONS IN JUNCTION SOLAR-CELLS, DIODES, AND TRANSISTORS

An analytical treatment of heavily doped transparentemitter devices is presented that includes the effects of bandgap narrowing, Fermi-Dirac statistics, a doping concentration gradient, and a finite surface recombination velocity S at the emitter surface. Transparency of the emitter to minority carrier is defined by the condition that the transit time Ttis much smaller than the minority carrier life time in the emitter Tp, Tt << Tp. As part of the analytical treatment, a self-consistency test is formulated that checks the validity of the assumption of emitter transparency for any given device. The transparent-emitter model is applied to calculate the dependence of the open-circuit voltage VOCof n+-p junction silicon solar cells made on low-resistivity substrates. The calculated VOCagrees with experimental values for high Sp(≧× 104cm/s) provided the effects of bandgap narrowing (modified by Fermi-Dirac statistics) are included in the transparent-emitter model. Copyright © 1979 by The Institute of Electrical and Electronics Engineers, Inc.