Method and apparatus for thin film quality control

A method of determining parameters of a photovoltaic thin film deposited on a substrate in a patterned photovoltaic panel, the panel being a plurality of individual photovoltaic cells, said method comprising:

• providing at least one photovoltaic cell panel and one or more optical sampling systems;
• enabling relative movement between the optical sampling system and the panel, and controlling the movement;
• identifying locations of individual photovoltaic cells on the panel;
• and,
• synchronizing each sampled point location such that the sampled point reading takes place, when the sampled point is located at a pre-determined place along the panel movement path.

A method of patterned thin film photovoltaic panel parameters determination, said method comprising:

• providing at least one patterned by individual photovoltaic cells thin film photovoltaic panel and one or more optical readout systems the optical system including at least a spectrometer;
• enabling relative movement between the optical system and the thin film photovoltaic panel and controlling the movement;
• identifying locations of the individual photovoltaic cells on the thin film photovoltaic panel;
• operating said spectrometer to readout the thin film parameters and synchronizing each reading of the thin film parameters such that the reading takes place, when the readout system is about the sampled point of the individual photovoltaic cell;
• and
• processing by a control unit operative to accept the spectrometer output and process it into the photovoltaic thin film parameters corresponding to the parameters of the sampled points of the individual photovoltaic cells.

A method of a thin film large area photovoltaic panel quality control, said method comprising:

• illuminating a section of a working plane by a polychromatic illumination, said working plane coinciding with said thin film plane;
• sampling a number of discrete points located in said illuminated section of the thin film and determining the spectral composition of the illumination reflected by each of said sampled points;
• comparing the actual spectral composition of each of said points with a theoretical stored in a memory spectrum composition;
• determining deviations of the determined spectral composition from said theoretical spectrum composition for at least one thin film parameter characterizing said point;
• and
• wherein the amount and severity of the deviations indicate the quality of the photovoltaic thin film.

A method of a set-up of a system for thin film patterned photovoltaic panel quality control, said method comprising:

• illuminating a line pattern on said photovoltaic thin film and reading said line by a fiber optics bundle having a first end arranged in a linear pattern and a second end arranged in a curved pattern;
• scanning the illuminated line by an illumination modulation device forming an illuminated spot on the first end of the fiber optics bundle and determining coordinates of the illuminated spot on the curved pattern;
• sequentially directing illumination emitted by the second end of each of the fibers by a scanning mirror rotating about an optical axis of a spectrometer into the spectrometer;
• and
• generating a calibration look-up-table relating coordinates of the spots residing on the line to their respective coordinates on the curved pattern.

A line to a curved surface conversion system for outputting a signal indicative of quality of a thin film photovoltaic panel, said system comprising:

• a polychromatic light source configured to illuminate at least a section of a thin film photovoltaic panel;
• a converting element configured to select a number of discrete sampled points residing on a straight line in said illuminated section and locate them on a curved line;
• a look-up table relating coordinates of each of the sampled points residing on a straight line in said illuminated section to their respective coordinates on the curved line;
• and
• a switch for directing the illumination emitted by the selected sampled points to a spectrometer operative to measure the intensity and spectral composition of each of said sampled points.

A method for thin film solar panel quality control, said method comprising:

• mapping locations of individual photovoltaic cells forming a thin film photovoltaic panel;
• capturing reflected illumination containing a plurality of wavelengths from the surface of at least one of individual photovoltaic cells and directing it to an intensity and wavelength sensitive detector;
• transforming said captured by the detector illumination intensity and wavelength such that said illumination intensity and wavelength provide a local indication on the individual photovoltaic cell parameters;
• and
• processing said captured illumination intensity and wavelength to derive at least one of a group of photovoltaic thin film parameters consisting of the thin film refractive index (n), thin film extinction coefficient (k), thin film surface roughness, spectrum and intensity of photoluminescence.

A high-speed wide format thin film photovoltaic panel quality control system, said system comprising;

• a illumination system illuminating a straight line in the working plane of the system,
• a high-speed optical switch, and a line to curve transforming element having a first end and a second end and configured to direct illumination reflected by a plurality of sampled points located on the straight line in the first end of the line to curve transforming element onto a curved line located in the second end of the line to curve transforming element, said second end being centered about the rotation axis of the optical switch;
• and
• wherein the switch is operative to sequentially convey the illumination reflected by the sampled points located on the second end curved line to a spectrometer with a sensor configured to measure the spectral composition of each of said sampled points.

A system for photovoltaic thin film quality control, said system comprising:

• one or more polychromatic illumination units operatively configured to illuminate a line in a working plane of the system, said plane coinciding with the photovoltaic thin film plane, and one or more forward and backward located thin film production stations;
• a sampling unit operatively configured to sample reflection of one or more sampled points located in the illuminated section and selected such that a straight line can be traced through all of the sampled points;
• a calibration facility configured to prepare a concordance table containing coordinates of sampled points on the measured photovoltaic thin film to their coordinates in the sampling unit, said facility including at least a scanning mirror movable along the illuminated section and sized such that at any location it reflects light from one sampled point only;
• a control unit operatively configured to synchronize operation of the illumination sources and the sampling unit, communicate with the forward and backward located thin film production stations, and process the sampled data;
• and
• wherein the processing of the sampled data by the control unit includes comparison of said data to a theoretical spectral data calculated for a predetermined set of parameters of at least one measured film.

A method of photovoltaic thin film quality control, said method comprising:

• selecting a plurality of discrete illuminated sampling points located on a line in a working plane of a thin film quality control system;
• imaging said plurality of discrete sampling points on a two dimensional optical switch such that image of each point exceeds the dimensions of one or more addressable elements of the switch;
• generating a concordance table between the locations of said points in the working plane and on the two-dimensional switch, wherein the location of the points on said switch are determined by the center of gravity of said points;
• optically switching between said points to enable sequential sampling of each of said points by a single detector;
• and
• determining the spectral composition of the illumination reflected or transmitted by said points.

A method of a photovoltaic thin film quality control, said method comprising:

• illuminating a section of a photovoltaic thin film by a polychromatic illumination source and forming on the thin film a continuous illuminated line;
• designating a plurality of discrete sampled points located on said illuminated line said points to be imaged onto an optical switch;
• generating a concordance between the coordinates of the above sampled points on the thin film and their coordinates on the optical switch;
• sequentially sampling each of said points by a single detector by optically switching between the points;
• and
• determining the spectral composition of the illumination reflected by the sampled points;
• deriving from the spectral composition at least one of a group of the photovoltaic thin film parameters consisting of the thin film refractive index (n), thin film extinction coefficient (k), thin film surface roughness, spectrum and intensity of photoluminescence;
• and
• extracting from the measurements of the thin film characteristics process specific control parameters, wherein the parameters are at least one of a group consisting of the energy gap, absorption, conductivity or crystallinity percentage.