Numerical Analysis of Electrical TCO / a-Si:H(p) Contact Properties for Silicon Heterojunction Solar Cells

Transparent Electrodes in Silicon Heterojunction Solar Cells: Influence on Contact Passivation

“…For such samples, a lowering of the measured V oc at high illumination intensities was sometimes observed. This evidence supports the belief that the WF of the n-type TCO, being lower than the one of a-Si:H(p), may result rather in a Schottky than an ohmic contact, causing a V oc drop and resistive losses under solar cell operation conditions [39], [42]. The value of n at 100 suns (n 100 ) was proposed as indicator for the strength of this effect [4].…”

“…9, the absence of variations in the high-illumination suns-V oc data is also remarkable. The perfect superposition of all the curves shown here, and the coincidence of their n 100 values indicates that-within the explored carrier density range-the ITO properties do not impact those of the presumed "Schottky contact" [39], [42].…”

“…These seemingly competing requirements have both implications toward the FF of high-efficiency SHJ devices. However, the FF loss observed for lowly doped TCO-contact films [4], [46], [47] cannot be explained by their higher WF, which instead should mitigate possible detrimental "Schottkycontact" effects [39], [42].…”

Molybdenum and tungsten oxide: High work function wide band gap contact materials for hole selective contacts of silicon solar cells

“…Their low net doping and high defect density make the optimization of the hole contact typically more challenging than that of the electron contact. As a minimum thickness (and doping) of the a-Si:H has to be a applied to form the junction [9,10] (ii), the parasitic photon absorption in the doped a-Si:H lowers the carrier generation in the absorber significantly [11]. (iii) The temperature stability of a-Si:H is limited to below 200°C [12], which calls for adapted process steps for back end processing (TCO, metallization) and module integration, both of which are hardly compatible with the well-established mainstream processes used for homojunction cells.…”

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

“…FF losses associated with heterocontact transport properties can be at least partially ascribed to the TCO/a-Si:H interface [10], [43]- [46]. Our experimental work with IBC-SHJ confirms the importance of this interface with respect to series-resistance losses; changes in the TCO layer composition have shown a relevant impact on total series resistance and FF of final devices (data not shown), as have changes in the deposition conditions of the doped a-Si:H layers.…”