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

Abstract

This paper presents an understanding of the fundamental carrier transport mechanism in hydrogenated amorphous silicon (a-Si:H)-based n/p junctions. These n/p junctions are, then, used as tunneling and recombination junctions (TRJ) in tandem solar cells, which were constructed by stacking the a-Si:H-based solar cell on the heterojunction with intrinsic thin layer (HIT) cell. First, the effect of activation energy (E a ) and Urbach parameter (E u ) of n-type hydrogenated amorphous silicon (a-Si:H(n)) on current transport in an a-Si:H-based n/p TRJ has been investigated. The photoluminescence spectra and temperature-dependent current-voltage characteristics in dark condition indicates that the tunneling is the dominant carrier transport mechanism in our a-Si:H-based n/p-type TRJ. The fabrication of a tandem cell structure consists of an a-Si:H-based top cell and an HIT-type bottom cell with the a-Si:H-based n/p junction developed as a TRJ in between. The development of a-Si:H-based n/p junction as a TRJ leads to an improved a-Si:H/HIT-type tandem cell with a better open circuit voltage (V oc ), fill factor (FF), and efficiency. The improvements in the cell performance was attributed to the wider band-tail states in the a-Si:H(n) layer that helps to an enhanced tunneling and recombination process in the TRJ. The best photovoltage parameters of the tandem cell were found to be V oc = 1430 mV, short circuit current density = 10.51 mA/cm 2 , FF = 0.65, and efficiency = 9.75%.

High Efficiency Inorganic/Inorganic Amorphous Silicon/Heterojunction Silicon Tandem Solar Cells

“…The tandem solar cell with the standard a-Si:H i -layer top sub-cell showed the V oc of 1.56 V, the J sc of 9.83 mA/cm 2 , the FF of 76.02%, and the PCE of 11.65%. These results are obviously better than those obtained in investigations of similar tandem configurations reported in the literature 5,9,22 , yet remain lower than the PCE of organic-inorganic silicon-based tandem cells 3,8,10,11 . The tandem solar cell fabricated with the a-SiGe:H i -layer top sub-cell showed a significant increase in J sc from 9.83 to 12.26 mA/cm 2 , while obtaining a remarkable decrease in V oc and FF from 1.56 (V) and 76.02% to 1.44 (V) and 67.01%, respectively, thereby leading to a slight increase of PCE from 11.65% to 11.84%.…”

“…Both organic-inorganic (perovskite/c-Si multi-junction) and inorganic-inorganic [p/i/n thin film silicon (p/i/n-TFS)/c-Si multi-junction] solar cell configurations have been investigated widely to achieve these band gap ranges 3,5,7–11 . In these devices, the tunneling-recombination junction plays a significant role in enhancing power conversion efficiency (PCE) 9 . Although the organic-inorganic tandem solar cells show higher initial device efficiency, the inorganic-inorganic type tandem devices are expected to show better stabilized performance in the long run.…”

Designing a hybrid thin‐film/wafer silicon triple photovoltaic junction for solar water splitting

“…The junction between the a‐Si:H cell and the nc‐Si:H cell have been previously studied . However, the junction between the nc‐Si:H cell and the silicon heterojunction (SHJ) cell is relatively unexplored . Moreover, in order to improve the current density of the multijunction solar cell, light management techniques need to be implemented.…”

“…[8][9][10] However, the junction between the nc-Si:H cell and the silicon heterojunction (SHJ) cell is relatively unexplored. 11,12 Moreover, in order to improve the current density of the multijunction solar cell, light management techniques need to be implemented. First, conventional texturing of the crystalline silicon substrate was considered in order to increase the light absorption within the cell, exploring its light trapping capabilities and the adhesion, crystallinity, and material quality of the nc-Si:H absorber layer.…”

First down converter multilayers integration in an industrial Si solar cell process

“…For example, an increase of 1°C above 25°C leads to a decrease of the SC efficiency by around 0.65% [3][4][5] and results in its faster aging. Several ways to improve the SC efficiency 6 are thus investigated such as tandem cells, 7,8 surface texturing, 9,10 antireflective layer, [11][12][13] or frequency conversion layer. 2,[14][15][16][17][18][19][20] In that respect, down conversion (DC) answers the thermalization issue by converting high energy photons to a greater number of lower energy photons with energies close to the Si-SC gap.…”