Phosphorus emitter and metal - grid optimization for homogeneous (n+p) and double-diffused (n++n+p) emitter silicon solar cells

Abstract

This work focuses on studying two types of structure: homogeneous and double-diffused emitter silicon solar cells. The emitter collection efficiencies and the recombination current densities were studied for a wide range of surface dopant concentrations and thicknesses. The frontal metal-grid was optimized for each emitter, considering the dependence on the metal-semiconductor contact resistivity and on the emitter sheet resistance. The best efficiency for n + p structures, η ≈ 25.5%, is found for emitters with thicknesses between (0.5-3) µm and surface doping concentrations in the range 2 x 10 19 cm -3 -4 x 10 18 cm -3 ; while the n ++ n + p structure a maximum efficiency of η ≈ 26.0% was identified for an even wider range of emitter profiles.

Co‐optimization of emitter profile and metal grid of selective emitter silicon solar cells

“…Therefore, the bottom part of Figure is mainly determined by J sc . This result is slightly different from that found by Sánchez et al . In that work, the V oc contour was symmetrically distributed, centered on moderate junction depth of about 1 µm in the lightly doped region.…”

“…The total shading factor F s is defined as the sum of F f and F b . In contrast to previous works , which used silicon dioxide for the passivation layer of the emitter, the SiN x produced by low temperature plasma‐enhanced chemical vapor deposition is more suitable for passivating an n‐type emitter in large‐volume production. The SRV is where a = 10 −3.9 , b = 0.29, c = 10 −11 , d = 0.74, e = 10 −40.28 , f = 2.2, and N 0 is the surface dopant concentration.…”

“…From the definition of sheet resistance, the sheet resistance of a textured emitter has the same value as a non‐textured emitter for the same emitter dopant profile. In contrast to previous works , which studied a 20 mm × 20 mm lab cell, this work uses a 125 mm × 125 mm cell with a two busbar layout. This is a typical size for large‐volume production.…”

“…Thus, the SRV is S n = 700 cm/s and the rear surface reflectance is R b = 75% . In previous works , a zero rear SRV was assumed, which is impossible in reality and overestimates base region electrical performance. Other simulation parameters are as follows: wafer thickness W of 200 µm, base dopant concentration of 10 − 16 /cm 3 , considering band gap narrowing , illumination of AM1.5G, and minority carrier lifetime of the base of 400 µs, limited by Auger and Shockley–Read–Hall. This minority carrier lifetime is lower than those used in the works of Cuevas and Sánchez and close to that in industrial manufacturing. The saturation current of the emitter is the area‐weighted sum of currents in the lightly and heavily doped parts. where J oe(heavily_doped) is fixed and independent of any change in the dopant profile of the lightly doped area, because it is determined by the laser doping process.…”

Simulations Based on the Cooptimization Procedure for Plated Contacts With a NiSi Interface

“…Demesmaeker et al [14] first described this procedure for homogeneous emitter (HE) and selective emitter (SE) solar cells. Then, Cuevas and Russel [15] used PC1D [16] to combine numerical simulations with analytical power loss calculations in order to generate HE efficiency contour plots for distinctive solar cells (i.e., laboratory and commercial devices), whereas Sanchez and Stem [17] focused on the comparison of HE and SE laboratory scale solar cells using only analytical solutions [18]. Recently, Wen et al [19] used analytical models to optimize SE industrial solar cells.…”