If I were trying to make a Raman setup on the cheap and had plenty of time to scan a sample, I think I would wavelength disperse the beam and scan a photodiode across it. Using a photodiode has the advantage of detailed spec sheets and sample circuit diagrams many places on the internet.
A solar cell is a photodiode. A photodiode might not be the best detector though.
Most commercial Raman spectrometers use CCDs (charge coupled devices) for detection, and these are relatively cheap and abundantly available: they are widely used in digital cameras. They are also fast. If you disperse the scattered light with a diffraction grating, a CCD array can easily detect a decent fraction of the relevant spectrum simultaneously, as opposed to sweeping the diffracted light past a single photodiode.
no, i mean is there any way to build a homemade raman spectroscope that detects carbon nanotubes other than use a solar panel and diffraction grating. it doesn't have to use a solar panel and diffraction grating. it can use any other components instead. it uses something other than a solar panel and diffraction grating instead. i don't think you understood that question.
Again, you show no signs of having watched that video. Do you have a HeNe laser? Do you have a notch filter? The only equipment you've mentioned is solar panels and diffraction gratings - now you say you won't use it, but you won't say what you will use. I think the only possible answer is "No, you won't be able to do this."