The interest in perovskite photovoltaics (PVs) has drastically increased in the last few years, both in the scientific community and solar industry, since these devices can offer a high light-to-electricity conversion efficiency at a low manufacturing cost, providing also many unique characteristics. According to the latest research reports, the market of perovskite solar cells (PSCs) is estimated to grow at a 34% compound annual growth rate (CARG) for 2020-2027. Although, to ensure the economic feasibility and competitive levelized cost of electricity (LCOE), critical challenges regarding their long-term stability, scaling up and manufacturing costs should be further considered and overcome.
For enabling the successful fabrication of very low-cost, stable and scalable PSCs, ambient air processed carbon-based hole transport material-free (C-based HTM-free) PV devices employing perovskites as light absorbers are considered the front runner to the market. This type of solar cell seems to be the most promising for achieving very low manufacturing costs due to the inexpensive carbon materials, very simple structure and full compatibility with printing fabrication techniques. Simultaneously, under this architecture, many instability issues that characterize the conventional noble metal-based PSCs are addressed. When the fabrication of these devices is combined with fully ambient air-processing, where sophisticated air/humidity-controlling systems are avoided, their mass production and commercialization are considered one significant step closer.
Up until now, the vast majority of PSCs have relied on the spin-coating of solar cell materials under inert fully controlled conditions, with the performance of devices that are developed by alternative techniques and under ambient atmosphere to lag far behind. This impedes the technology transfer from the laboratory to industrial large-scale production. Thus, the investigation of new scalable techniques should be thoroughly considered. Some of the alternatives that have been already applied are blade-coating, slot-die coating, spray-coating and inkjet-printing. Amongst them, inkjet-printing stands out as a digital deposition approach for solution-based materials that is characterized for its scalability, fast material deposition with high accuracy and low waste, which also allows for the formation of fine patterns of printed inks at a high resolution. To date, even though the studies on inkjet-printed PSCs are only few, substantial achievements have been made, with the record efficiencies for small-sized C-based PV devices to be on the order of 12%.
One of the aims of Brite Solar is to increase the technology readiness level (TRL) of PSCs for many pioneer and niche applications. More specifically, the company aims to deliver fully printed large-sized (>400 cm2) perovskite solar modules (PSMs) (Fig.1) utilizing drop-on-demand inkjet-printing, as well as novel nanostructures and perovskite materials, that will increase the competitiveness of this technology for its entering the PV market, all developed by Brite Solar Engineers and Scientists. Very recently, a breakthrough in the upscaling of fully-printed ambient air processed C-based HTM-free PSMs has been achieved: efficiencies on the order of 10% (in the active area of PV) under 1 sun illumination on an unprecedented 200 cm2 active area, is the main topic of our presentation, also demonstrating noteworthy stability under different accelerated ageing conditions (according to the ISOS protocols).