Frame and transparent element

The frame for the future panel can be made of wooden slats or aluminum corners here http://max64.ru/

The second option is preferable for a number of reasons:

Aluminum is a light metal that does not put a heavy load on the supporting structure on which the battery is planned to be installed.
When carrying out anti-corrosion treatment, aluminum is not affected by rust.
Does not absorb moisture from the environment, does not rot.
When choosing a transparent element, it is necessary to pay attention to parameters such as the refractive index of sunlight and the ability to absorb infrared radiation.

The efficiency of photocells will directly depend on the first indicator: the lower the refractive index, the higher the efficiency of silicon wafers.

The minimum light reflection coefficient for plexiglass or its cheaper version - plexiglass. The refractive index of polycarbonate is slightly lower.

It depends on the value of the second indicator whether the silicon photocells themselves will heat up or not. The less the plates are exposed to heat, the longer they will last. IR radiation is best absorbed by special heat-absorbing plexiglass and glass with IR absorption. A little worse - ordinary glass.

If possible, the best option would be to use anti-reflective transparent glass as a transparent element.