Does it look good to have a paper without your PhD advisor as an author?
The comments here seem to cover the ground pretty well. Having publications of any sort is a plus. Having lots of collaborations is a big plus and well serve you well in your future work, not just in applications. 

But in some fields it is more or less necessary to have your advisor, and maybe others, on publications that arise from your dissertation work. In other fields that would be unusual. 

However, don't obsess over this issue. Do the best work you can and publish the work as best you can with appropriate authorship for the work and for the field. After you finish the degree and become more independent of your advisor, you will probably write sole author papers. But if you have the opportunity for a sole author publication as a student, don't pass it up. 

But don't neglect the synergistic power of collaboration in what you do.