An examination of the 'tunnel junctions' in triple junction a-Si:H based solar cells: modeling and effects on performance

Current transport studies of amorphous n/p junctions and its application in a‐Si:H/HIT‐type tandem cells

“…Photogenerated electrons in the top cell and holes in the bottom cell are driven into the TRJ where all the carriers must recombine . It has been observed that the classical Shockley–Read–Hall recombination formalism is not enough to understand the experimentally observed characteristics of tandem solar cell such as the V oc and FF .…”

“…Photogenerated electrons in the top cell and holes in the bottom cell are driven into the TRJ where all the carriers must recombine . It has been observed that the classical Shockley–Read–Hall recombination formalism is not enough to understand the experimentally observed characteristics of tandem solar cell such as the V oc and FF . There was an attempt to introduce a hypothesis of special recombination layers or “x‐layer” along with a graded band gap around it, in order to explain or improve the carrier transport across n/p junction of a tandem cell .…”

High efficiency triple junction thin film silicon solar cells with optimized electrical structure

“…It has been suggested by Hou et al . that a highly defective layer with a reduced band gap at the n/p interface, conduction‐band‐edge grading of the n‐type layer, and valence‐band‐edge grading of the p‐type layer are needed in simulations of effective contacts. Including grading of the conduction and valence band edges allows simulations of the tunneling behavior of the carriers, and such a structure is needed to interconnect the component cells without V oc and FF losses.…”

“…The V oc loss of the a‐Si:H/a‐SiGe:H double‐junction solar cell ( V oc‐top + V oc‐bot > V oc‐tandem ) may arise for the following possible reasons: (i) A low recombination rate (low mid‐gap or bandtail defect states in the n/p region) at the TRJ that results in piling up of the photo‐generated electrons collected from the a‐Si:H cell and photo‐generated holes collected from the a‐SiGe:H cell . (ii) A slow supply of collected carriers to the TRJ, which also leads to the piling up of photo‐generated carriers from adjacent component cells . (iii) Photo‐generated electrons from the bottom a‐SiGe:H cell back‐diffusing into the TRJ structure and a reduction in the net supply of holes that recombine with electrons tunneling through the mid‐gap or bandtail defect states.…”

Optimization of Recombination Layer in the Tunnel Junction of Amorphous Silicon Thin-Film Tandem Solar Cells

“…For high stabilized efficiency tandem cell applications, a good n/p junction must have very high recombination rates, negligible optical absorption, and an ohmic characteristic with a low series resistance in order to improve the carrier transport [3][4][5][6]. Various recombination layers, such as a-SiC:H [7], metal oxides [8], microcrystalline n + layer [9], and n + /p + recombination layer [10] have been introduced between the n and p layers to promote carrier recombination.…”