Perovskites for Photovoltaic Efficient Conversion Technology (PERPHECT)
The topic of the PERPHECT research project is to optimize the performances of standard perovskite photovoltaic cells, introduce new concepts for the separation of the photo-generated charge carriers, replacing some of the deficient materials with others more affordable and environmental friendly and develop low costs fabrication technologies easily adaptable to large scale production allowing the fabrication of flexible solar cells able to collect not only the sun-light but also the light coming from the artificial sources used, especially during the winter, inside office buildings or large malls.
The standard perovskite solar cell (PSC) is formed by: a transparent conducting electrode (FTO), compact and/or mesoporous layers of TiO2 as electron transporting material (ETM), the halide perovskite CH3NH3PbI3-xClx (MAPI) layer as light absorbing material, a layer of (spiro-OMeTAD) acting as hole transporting material (HTM) and a counter electrode (Ag, Mo/Ag, Au).
Scientific and innovative challenges with relevance for direct practical use, foreseen at the start of the project:
– Replacing the actual transparent conducting electrodes based on ITO or FTO (In, Sn are deficient materials, while F can be potentially harmful for the environment) with metal nanowebs covered with Al doped ZnO.
– Optimizing the interfaces between the halide perovskite light absorber and the electron and hole transporters.
– Enhancing the charge collection by introducing more efficient active layers in intimate contact with the light absorber.
– Fabrication of solar cells with transparent electrodes on both sides. Deposited on glass windows, these cells will harvest not only the Sun light but also the indoor light which otherwise is wasted.
– Use of printing-type technology for fabricating the test structures at pre-industrial
The project included both basic and applied research in order to understand the physics behind the working principle of the new halide perovskite absorber, as well as in finding technological ways to optimize the overall efficiency by enhancing the charge collection and minimizing the observed deleterious effects and succeed at the end of the project to develop a low cost technology and build up a laboratory demonstrator for printing solar cells on solid or flexible substrates. The evolution of our progress during the project in terms of PCE values in standard PSC is depicted below.
As we will describe further, we have learn during the project that despite the large value attained for the PCE the further progress towards up-scaling and commercialization is faltered by serious stability (aging) problems, not known at the beginning of the project. Therefore, large unforeseen efforts were made to increase the stability of the perovskite solar cells and understand the physical reasons behind variations in the solar PSC electrical response. As it will be detailed in the following we have obtained the best stability level reported so far for standard PSC (glass/FTO/TiO2/CH3NH3PbI2.6Cl0.4/Au).
A number of 12 ISI publications, with a total 52.8 impact factor, one patent application and 4 topics for PhD theses resulted during the project. For more details see the web page of the project (http://8see.infim.ro/).