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Sample Holders

A sample holder is a custom PCB with several spring-loaded probes positioned according to the device structure. The traces connect to a custom connector, which in turn connects through a cable back to the source measure units. Devices on a sample holder are usually back-contacted. This simplifies the design of the sample holder and avoids having the contact probes block the incident light. Devices are pressed onto the spring-loaded contacts using a metal mask with openings for the incident light. The mask can be fixed in place using screws or magnets depending on the design.

Sample holder example designs

Below you can find several realized designs.

1x1

1x2

2x1

3x1

3x1s

2x2

3+1

4x1

3x2

3x2m

3x2s

4x2

4x2l

4x2m

4x2s

8o

Sample holder details

sample-holder
Example of a sample holder for 32 devices distributed across 4 substrates. On the bottom left, temperature, humidity, and luminosity sensors can be found.

The figure above shows an example of a sample holder for 32 devices in a small area. Since the devices are always grouped together in the same order, smaller and more flexible Samtec® cables are used instead of eight bulky DB25 connectors. These cables also carry the signals used to measure the environmental sensors present on the sample holder.

Testing each sample holder is not reliable when using lab-level devices, since failing to measure a signal may be due to a failing device rather than a fault in the sample holder. For each type of sample holder, a custom PCB with the same layout as the solar cells is therefore made. The solar cells are substituted with resistors to reliably test the entire connection chain.