OPV technology offers the possibility to produce semitransparent colourless cells, providing a clear and undistorted image when looking through the device. It can be perfectly integrated in building façades, offering great potential for electricity production units to penetrate in urban areas. Most photovoltaic installations in buildings currently consist of modules with opaque cells that are installed on the roof, in opaque façade surfaces or integrated in glass façades, generating shadows and preventing uniform visibility. The use of transparent photovoltaic cells will significantly increase the electricity-generating surface in building envelopes, while at the same time providing clear and undistorted vision. Within the EU-funded project SOLPROCEL (Solution processed high performance transparent organic photovoltaic cells), partners from four countries put together their experience, successfully developing three building-integrated OPV cells of high efficiency, transparency and stability using only solution-processing processes. The project focused on developing new nano- and organic materials necessary for obtaining high-performance semi-transparent solar cells using formulations that are solution-processable. These materials served to obtain stable devices that raised the efficiency of semi-transparent OPV cells from 5.6 to 7 %. Project partners synthesised new cross-linkable donor acceptor polymers to enhance light harvesting in the infrared region and ensure long-term thermal stability of the cells. Another part of the project was geared towards developing materials for other parts of the solar cell that are not related to the active parts of the cell. Using solution-processable formulations, researchers synthesised electrode materials based on silver nanowires, semiconducting carrier transport layers based on new metal oxide nanoparticle inks and buffer layers based on organic-inorganic materials. Focus was also placed on identifying the main failure mechanisms in these semi-transparent organic solar cells and creating cell configurations for more stable devices. Researchers showed that proper filtering in addition to a new procedure that stabilises the blend’s nanomorphology can eliminate the detrimental effect of ultraviolet light. For opaque devices oriented horizontally facing the sky, the expected lifetime was found to exceed seven years. For cells oriented vertically, such as those integrated in building façades and windows, lifetime can exceed 10 years. SOLPROCEL made a significant step towards improving semi-transparent photovoltaic elements, allowing buildings to generate electric energy by semi-transparent solar modules.
Transparent, solar cells, organic photovoltaics, building-integrated photovoltaics, SOLPROCEL