Three-dimensional numerical analysis of hybrid heterojunction silicon wafer solar cells with heterojunction rear point contacts

Abstract

This paper presents a three-dimensional numerical analysis of homojunction/heterojunction hybrid silicon wafer solar cells, featuring front-side full-area diffused homojunction contacts and rear-side heterojunction point contacts. Their device performance is compared with conventional full-area heterojunction solar cells as well as conventional diffused solar cells featuring locally diffused rear point contacts, for both front-emitter and rear-emitter configurations. A consistent set of simulation input parameters is obtained by calibrating the simulation program with intensity dependent lifetime measurements of the passivated regions and the contact regions of the various types of solar cells. We show that the best efficiency is obtained when a-Si:H is used for rear-side heterojunction point-contact formation. An optimization of the rear contact area fraction is required to balance between the gains in current and voltage and the loss in fill factor with shrinking rear contact area fraction. However, the corresponding optimal range for the rear-contact area fraction is found to be quite large (e.g. 20-60 % for hybrid front-emitter cells). Hybrid rear-emitter cells show a faster drop in the fill factor with decreasing rear contact area fraction compared to front-emitter cells, stemming from a higher series resistance contribution of the rear-side a-Si:H(p+) emitter compared to the rear-side a-Si:H(n+) back surface field layer. Overall, we show that hybrid silicon solar cells in a front-emitter configuration can outperform conventional heterojunction silicon solar cells as well as diffused solar cells with rear-side locally diffused point contacts.

Lateral transport in silicon solar cells

“…In SHJ literature, for both experiment [11,21] and simulation [11,15,27], it was found that rear-junction devices benefit from lateral transport in the silicon absorber, while front-junction devices do not. Usually, the contact at the front-side of SHJ front-junction devices is the p-contact.…”

Heterojunction solar cells with 23% efficiency onn-type epitaxial kerfless silicon wafers

“…The cells in this study had an emitter on the back side, which was the side opposite to the illuminated side . For the conventional front‐emitter HJ structure, the p ‐layer thickness is determined considering the absorption loss and electrical properties of the p ‐layer.…”

“…In this work, we aimed to the efficiency of epi‐Si HJ solar cells by reducing SFs and applying a rear‐emitter structure . We performed spatial current density ( J ) mapping of epi‐Si HJ solar cells by spectral response mapping (SR‐MAP).…”

Thin absorbers for defect-tolerant solar cell design

“…The uncontaminated wafers are simulated in Sentaurus Device [17] using the model from [18] with parameters from [19], including the treatment of ITO as a metal. The doping of the/?-a-Si:H layer was increased to 6><10 13 cm" 3 to account for the high pFF in the Suns-Foe measurements.…”