Shading effects in back-junction back-contacted silicon solar cells

Abstract

One of the most often mentioned advantages of back-junction back-contacted silicon solar cells is that this cell structure has no shading losses, because metallization fingers and busbars are both located on the rear side of the solar cell. However, this is only true if only optical shading losses are regarded. In this work electrical shading losses due to recombination in the region of base busbar and fingers are analyzed using two-dimensional numerical device and network simulations. The base doping dependence of these effects is investigated as well as the influence of the rear side passivation. The results of the simulations are compared with EQE maps of back-junction solar cells. The influence of the busbars is quantified and the influence on the overall cell performance is discussed

Back-Contacted Silicon Heterojunction Solar Cells With Efficiency >21%

“…Conversely, the IBC-SHJ device FF is 73.0%, which is significantly lower than any typical high-performance Std-SHJ device. Based on spectral response and light-beam-induced current measurements, we link the still relatively modest J sc gain in our IBC-SHJ devices (versus our best Std-SHJ device) to not fully minimized parasitic absorption losses (both in the short-and long-wavelength parts of the spectrum), rather than to electrical shading effects [30], [31]. Further details on this topic will be the subject of future research.…”

Back-Contacted Silicon Heterojunction Solar Cells: Optical-Loss Analysis and Mitigation

“…This can result in J sc losses. This effect is known as electrical shading and has been extensively investigated both for homojunction and heterojunction back-contacted devices [32]- [34]. Eventually, back-contacted SHJ devices require bulk materials with sufficiently long carrier diffusion lengths to perform at their best [35], [36].…”

Simulation Results: Optimization of Contact Ratio for Interdigitated Back-Contact Solar Cells

“…The dimensions of point contacts should be optimized properly with respect to contact pitch and area; otherwise, the solar cells having line contact will behave similarly as the solar cells having point contact. To get the advantages of point contact, the contact pitch should be optimized with respect to the diffusion length [13] and emitter coverage [15,37] because this affects the lateral carrier transport.…”

“…IBC solar cells are fabricated with different dimensions of emitter and BSF [13]. The emitter of IBC solar cells is chosen not only wider than BSF to increase short circuit current [14] but also it is optimized with respect to BSF to reduce the effect of electrical shading or EQE losses [15]. The contact opening of emitter and BSF is another important parameter in the designing of IBC solar cells because it is responsible for power [16] and series resistance loss [17].…”

“…For modeling, we used a software tool called Quokka, which is able to simulate silicon solar cell devices in 1D/2D/3D [27]. The back surface of IBC solar cell looks like ZEBRA crossing which is symmetric around one emitter and BSF [28] that is why the simulation of unit cell, which consists of half emitter and BSF, resembles the behavior of a complete IBC structure [15,16,20,24]. In this work, we are simulating the unit cell of IBC structure in three dimension.…”