Q:

Can I submit a review paper to a journal without being invited?

I am currently in the process of waiting for PhD verdict. I have submitted the thesis last 2 weeks for examination and I am thinking while waiting for PhD verdict, I want to write a review paper on my subject. The reason is because I have ran out results from my PhD study for publication and I reckon why not try on reviewing the subject I am studying. My area of research is biological science. My question is whether it is possible to write a review to journal without being invited to do so. 

A:

Yes, it is absolutely possible to write a review paper without being invited to do so.
How do I know this?
I've done it, several times, in the biological sciences.
The key is to recognize that the review needs to be invited at some point, but that point need not be "before you've written anything down*. If you have a target journal, and you think it is a decent fit for the review paper, I would suggest that you find the email for the appropriate section editor (or the Editor-in-Chief if there is none) and write them a polite email inquiring as to whether or not they would be interested in inviting a review on X topic, a draft of which is attached. Articulate why you think this is useful and interesting to their readership, and hope for the best.
And before we get on the "A PhD isn't enough clout to write a review", my first review was published with an undergraduate as the primary author.

A:

You should check with the journal you plan to submit to. Many do not accept unsolicited review articles, so it would be a waste of time to write something that won't get considered.

A:

I would like to offer a different opinion, and support writing a review on your PhD area of expertise. 
First, it could be a useful learning opportunity for OP, as it gives an incentive to do a literature review by setting a plausible goal for an otherwise tedious task. I also oftentimes find that committing something to writing can be beneficial to the uptake of information. 
Second, in many fields a review paper is indeed often co-written with an advisor; in some cases the student may even do the bulk of the initial writing. In this context, I would suggest either speaking to your supervisor before writing to gauge his interest in co-authoring a review paper with you, or speaking to him after an initial draft is completed to allow him to have a judgement on the work. 
Third, there can certainly be journals where reviews are not invite-only. As long as your supervisor is willing, it would not hurt to send it and see what comes of it. As there are so many journals out there today, I don't think it is impossible to find one with an editor interested in the manuscript. 

