The efficiency of silicon solar cells has a large influence on the cost of most photovoltaics panels. Here, researchers from Kaneka present a silicon heterojunction with interdigitated back contacts reaching an efficiency of 26.3% and provide a detailed loss analysis to guide further developments.

Silicon heterojunction solar cell with interdigitated back contacts for a photoconversion efficiency over 26

n-Type Si solar cells with passivating electron contact: Identifying sources for efficiency limitations by wafer thickness and resistivity variation

Laser contact openings for local poly-Si-metal contacts enabling 26.1%-efficient POLO-IBC solar cells

Exceeding conversion efficiency of 26% by heterojunction interdigitated back contact solar cell with thin film Si technology

In this study, we present a novel application of thin magnesium fluoride films to form electron-selective contacts to n-type crystalline silicon (c-Si). This allows the demonstration of a 20.1%-efficient c-Si solar cell. The electron-selective contact is composed of deposited layers of amorphous silicon (∼6.5 nm), magnesium fluoride (∼1 nm), and aluminum (∼300 nm). X-ray photoelectron spectroscopy reveals a work function of 3.5 eV at the MgF2/Al interface, significantly lower than that of aluminum itself (∼4.2 eV), enabling an Ohmic contact between the aluminum electrode and n-type c-Si. The optimized contact structure exhibits a contact resistivity of ∼76 mΩ·cm(2), sufficiently low for a full-area contact to solar cells, together with a very low contact recombination current density of ∼10 fA/cm(2). We demonstrate that electrodes functionalized with thin magnesium fluoride films significantly improve the performance of silicon solar cells. The novel contacts can potentially be implemented also in organic optoelectronic devices, including photovoltaics, thin film transistors, or light emitting diodes.

Magnesium Fluoride Electron-Selective Contacts for Crystalline Silicon Solar Cells

An energy conversion efficiency of 25.1% was achieved in heterojunction back contact (HBC) structure Si solar cell utilizing back contact technology and an amorphous silicon thinfilm technology. A new patterning process was established, and it was applied to the fabrication process of HBC cells. In addition, the unique technology of the surface mount technology concept contributed to the superior performance of HBC cell. A short circuit current density (J
 sc
) and an open-circuit voltage (V
 oc
) were 41.7 mA/cm2 and 736 mV, respectively. The high J
 sc
 as well as the high Voc indicates the strength of HBC structure cell. Besides, a high fill factor of 0.82 was obtained, which shows that HBC structure cell does not have any fundamental critical losses caused from series resistance or shunt resistance. Such high values of I-V parameter means that the patterning process was properly performed.

Development of Heterojunction Back Contact Si Solar Cells

PROBLEM TO BE SOLVED: To enable improvement in reliability of a photoelectric conversion device while inhibiting deterioration in characteristics of the photoelectric conversion device formed by electrically connecting a heterojunction back contact cell and a wiring sheet.SOLUTION: A heterojunction back contact cell (10) comprises: a first conductivity type or a second conductivity type semiconductor substrate (1); a first conductivity type amorphous semiconductor film (3) and a second conductivity type amorphous semiconductor film (5) which are provided on one side of the semiconductor substrate (1); a first electrode (11) on the first conductivity type amorphous semiconductor film (3); and a second electrode (12) on the second conductivity type amorphous semiconductor film (5). A center-to-center distance between neighboring and closest electrodes having the same polarity is not less than 1 mm and not more than 3.5 mm.SELECTED DRAWING: Figure 1

Hetero junction type back contact cell and photoelectric conversion device

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element capable of improving performance and reliability than the prior art and to provide a manufacturing method of the same.SOLUTION: The photoelectric conversion element includes: a first irregularity 8 and a second irregularity 9 provided on one surface of a semiconductor substrate 1; a first i-type semiconductor film 2 and a first conductive type semiconductor film 3 provided on the first irregularity 8; a second i-type semiconductor film 4 and a second conductive type semiconductor film 5 provided on the second irregularity 9; an electrode layer 11 for a first conductive type provided on the first conductive type semiconductor film 3; and an electrode 12 for a second conductive type provided on the second conductive type semiconductor film 5. The first irregularity 8 and the second irregularity 9 are different in shape.

Photoelectric conversion element and manufacturing method of the same

Provided is a photoelectric conversion element which has improved element characteristics by suppressing increase in the contact resistance between an amorphous semiconductor layer that contains an impurity and an electrode that is formed on the amorphous silicon layer. This photoelectric conversion element (10) is provided with a semiconductor substrate (12), a first semiconductor layer (20n), a second semiconductor layer (20p), a first electrode (22n) and a second electrode (22p). The first semiconductor layer (20n) has a first conductivity type. The second semiconductor layer (20p) has a second conductivity type that is opposite to the first conductivity type. The first electrode (22n) is formed on the first semiconductor layer (20n). The second electrode (22p) is formed on the second semiconductor layer (20p). The first electrode (22n) and/or the second electrode (22p) contains a plurality of metal crystal grains. The average crystal grain size of the metal crystal grains in the in-plane direction of the electrode is larger than the thickness of the electrode.

A cyclonic separation assembly having a low residence time plenum arranged in a fluidized bed reactor vessel

This invention provides a heterojunction back-contact cell that exhibits high conversion efficiency and reduced conversion-efficiency variability. Said heterojunction back-contact cell contains a semiconductor substrate (1) and also contains a first i-type semiconductor film (2) and a second i-type semiconductor film (4), both of which are provided on the surface of the semiconductor substrate. A p-type semiconductor film (3) is provided on top of the first i-type semiconductor film (2), and an n-type semiconductor film (5) is provided on top of the second i-type semiconductor film (4). The ratio of a first footprint, said first footprint being the footprint of the first i-type semiconductor film (2) on the surface of the semiconductor substrate (1), to the sum of said first footprint and a second footprint, said second footprint being the footprint of the second i-type semiconductor film (4) on the surface of the semiconductor substrate (1), is between 0.5 and 0.73, inclusive.

Takeshi Hieda

Papers

Development of Heterojunction Back Contact Si Solar Cells

Hetero junction type back contact cell and photoelectric conversion device

Photoelectric conversion element and manufacturing method of the same

A cyclonic separation assembly having a low residence time plenum arranged in a fluidized bed reactor vessel

Heterojunction back-contact cell and method for manufacturing heterojunction back-contact cell