A lightly doped p-type silicon base has

PHYSICS · Multi-part · Fermi University Physics · Condensed Matter, Materials & Soft Matter · Earth, Climate & Energy Physics · Electronic transport in solids

Energy from Physics, Ch The illuminated junction: generation, collection and the cell's characteristic

Problem

A lightly doped p-type silicon base has NA=5×1015 cm−3N_A = 5\times10^{15}\,\mathrm{cm^{-3}}, electron mobility μn=1350 cm2 V−1 s−1\mu_n = 1350\,\mathrm{cm^2\,V^{-1}\,s^{-1}} and recombination lifetime τ=50 μs\tau = 50\,\mu\mathrm{s} at 300 K300\,\mathrm{K}, where ni=1×1010 cm−3n_i = 1\times10^{10}\,\mathrm{cm^{-3}}. Treat the base as long compared with its diffusion length and work at low injection. The emitter side of the junction contributes a further 5×10−14 A cm−25\times10^{-14}\,\mathrm{A\,cm^{-2}} to J0J_0. Under 1000 W m−21000\,\mathrm{W\,m^{-2}} the cell has Jsc=38 mA cm−2J_{sc} = 38\,\mathrm{mA\,cm^{-2}}. ((a)) Find the base's contribution to the diffusion dark current and the cell's total J0J_0. ((b)) Find the cell's open-circuit voltage, its fill factor from Green's fit and its efficiency. ((c)) Gettering raises the base lifetime to 200 μs200\,\mu\mathrm{s}. Find the new total J0J_0 and the new open-circuit voltage.

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