1. Solar cells are a little smaller and lighter than before.

2. Solar cells are little smaller and lighter than before.

3. Solar cells are much smaller and lighter than before.

(#3 is grammatical, right? What about #1 and #2? Are they grammatical? What is the difference between #1 and #2?)

2 answers

1 and 3 are good.
For #2, custom demands that we use the article in this sentence.