Please give details of the photodiode module, a link to the product or datasheet. You should post such things without being asked. It should be obvious that we will need to see them. Have you read the forum guidelines in the sticky post yet?
It may be possible to arrange your photodiodes in, for example, a 12x12 matrix. This will require only 24 Arduino pins, 12 digital output pins for the rows and 12 analog input pins for the columns. The Arduino sketch would scan the rows one by one and read the 12 column pins.
However, the circuit on the module may make this idea impossible.