CleanTech Acquisition Corp. filed SEC Form 8-K: Entry into a Material Definitive Agreement, Completion of Acquisition or Disposition of Assets, Amendments to the Registrant’s Code of Ethics, or Waiver of a Provision of the Code of Ethics, Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing, Unregistered Sales of Equity Securities, Material Modification to Rights of Security Holders, Changes in Registrant’s Certifying Accountant, Changes in Control of Registrant, Leadership Update, Amendments to Articles of Incorporation or Bylaws; Change in Fisca