Best Performance of n<sup>+</sup> - p Crystalline Silicon Junction Solar Cells at 300 K, Due to the Effects of Heavy Doping and Impurity Size. I

Abstract

The effects of heavy doping and donor (acceptor) size on the hole (electron)-minority saturation current density J Eo (J Bo), injected respectively into the heavily (lightly) doped crystalline silicon (Si) emitter (base) region of n +-p junction, which can be applied to determine the performance of solar cells, being strongly affected by the dark saturation current density: J o ≡J Eo + J Bo , were investigated. For that, we used an effective Gaussian donor-density profile to determine J Eo , and an empirical method of two points to investigate the ideality factor n, short circuit current density J sc , fill factor (FF), and photovoltaic conversion efficiency η, expressed as functions of the open circuit voltage V oc , giving rise to a satisfactory description of our obtained results, being compared also with other existing theoretical-and-experimental ones. So, in the completely transparent and heavily doped (P-Si) emitter region, CTHD(P-Si)ER, our obtained J Eo-results were accurate within 1.78%. This accurate expression for J Eo is thus imperative for continuing the performance improvement of solar cell systems. For example, in the physical conditions (PCs) of CTHD (P-Si) ER and of lightly doped (B-Si) base region, LD(B-Si)BR, we obtained the precisions of the order of 8.1% for J sc , 7.1% for FF, and 5% for η, suggesting thus an accuracy of J Bo (≤ 8.1%). Further, in the PCs of completely opaque and heavily doped (S-Si) emitter region, COHD(S-Si)ER, and of lightly doped (acceptor-Si) base region, LD(acceptor-Si)BR, our limiting η-results are equal to: 27.77%,…, 31.55%, according to the E gi-values equal to: 1.12eV ,…, 1.34eV, given in various (B,…, Tl)-Si base regions, respectively, being due to the acceptor-size effect. Furthermore, in the PCs of CTHD (donor-Si) ER and of LD(Tl-Si)BR, our maximal η-values are equal to: 24.28%,…, 31.51%, according to the E gi-values equal to: 1.11eV ,…, 1.70eV, given in various (Sb,…, S)-Si emitter regions, respectively, being due to the donorsize effect. It should be noted that these obtained highest η-values are found to be almost equal, as: 31.51%% 31.55%, coming from the fact that the two obtained limiting J-values are almost the same.