In a previous post I reported on a number of patent applications related to transparent solar panel technology that could be manufactured by a spray-on process. This technology was being developed by Prof Xiaomei Jiang under a research agreement with New Energy Technologies Inc. This company has now changed its name to Solar Window Technologies Inc. and there is much less evidence of the spray-on approach in their technical information suggesting that they are less confident that spraying will be a viable manufacturing route.
The patent applications have been going through examination and until quite recently there had been no granted patents emerging with the spray-on process as the key manufacturing method. However, on 4 Aug 2015 the US20130255757 application was granted as US9099605 and as far as I am aware becomes the first granted patent with a spray-on process for PV panels.
I noticed that the first claim had to be modified before the examiner would allow it. It has been somewhat narrowed in scope to include a 48h at 60°C heating step for the P3HT and PCBM before spraying multiple layers to a final thickness of between 200 and 300nm. It was necessary to include this to avoid prior art found in the scientific literature which indicated a spray method but the layer needed to be thicker than 1.2 micron. Other prior art also made mention of the heating requirements but failed to specify the layer thickness. Similarly, where layer thickness was specified in the prior art, it did not teach the heating steps were essential.