Photovoltaic devices with narrow scribes and methods and systems for forming the same
According to the embodiments provided herein, a method for scribing a layer stack of a photovoltaic device can include directing a laser scribing waveform to a film side of a layer stack. The laser scribing waveform can include pulse groupings that repeat at a group repetition period of greater than or equal to 1.5 μs. Each pulse of the pulse groupings can have a pulse width of less than or equal to 900 fs.
1 . A method for scribing a layer stack of a photovoltaic device comprising:
directing a laser scribing waveform to a film side of a layer stack, whereby a scribe is formed through one or more scribed layers of the layer stack, and wherein:
the laser scribing waveform comprises pulse groupings that repeat at a group repetition period of greater than or equal to 1.5 μs,
each of the pulse groupings comprises two or more pulses that repeat at a pulse repetition period of less than or equal to 100 ns,
each of the two or more pulses have a pulse width of less than or equal to 900 fs, and
the layer stack includes a substrate and one or more intervening layers disposed between the one or more scribed layers and the substrate, and wherein the scribe is formed without traversing the one or more intervening layers.
2 . The method of claim 1 , comprising generating relative motion between the laser scribing waveform and the layer stack at a scan rate, wherein the scan rate is greater than or equal to 1 m/s.
3 . The method of claim 1 , wherein each of the two or more pulses has a beam diameter greater than or equal to 0.5 μm and less than or equal to 20 μm.
4 . The method of claim 1 , wherein each of the two or more pulses has a pulse energy less than or equal to 10 μJ.
5 . The method of claim 1 , wherein each of the two or more pulses has a wavelength between 300 nm and 1,100 nm.
6 . The method of claim 1 , wherein each of the two or more pulses has a wavelength between 300 nm and 600 nm.
7 . The method of claim 1 , wherein the one or more scribed layers of the layer stack comprises an absorber layer, and wherein the absorber layer comprises cadmium and tellurium.
8 . The method of claim 7 , wherein the one or more scribed layers of the layer stack comprises a transparent conductive oxide layer.
9 . The method of claim 7 , wherein the one or more scribed layers of the layer stack comprises a back contact layer formed adjacent to a conductive layer.
10 . The method of claim 1 , wherein the scribe defines a contour that extends through a laser effected width of the one or more scribed layers.
11 . The method of claim 10 , wherein the laser effected width is less than or equal to 40 μm.
12 . The method of claim 10 , wherein the contour comprises sidewalls that extend from a portion of the one or more scribed layers adjacent the laser effected width to a trough.
13 . The method of claim 12 , wherein the trough defines a portion of the contour where at least 99% of the thickness of the one or more scribed layers is removed.
14 . The method of claim 12 , wherein the trough defines a trough width less than or equal to 15 μm.
15 . The method of claim 14 , wherein a removal width is defined by the sidewalls at a 90% thickness of the one or more scribed layers, and a ratio of the removal width to the trough width is greater than or equal to 5.
16 . The method of claim 14 , wherein a removal width is defined by the sidewalls at a 90% thickness of the one or more scribed layers, and a ratio of the removal width to the trough width is in a range between about 12 and about 25.
17 . The method of claim 12 , wherein the sidewalls define a maximum angle α formed with respect to the first surface of the one or more scribed layers, and the maximum angle α is acute.