As global energy demands rise with population growth and industrialization, the need for efficient and cost-effective renewable energy sources is urgent. Perovskite solar cells (PSCs) have emerged as a powerful contender with their impressive power conversion efficiency (PCE) exceeding 25%. However, these figures have so far been achieved in laboratory environments using spin-coating method, highlighting a significant gap when it comes to scalable production techniques such as Roll-to-Roll (R2R) deposition, that could feasibly support mass manufacturing. Overcoming this hurdle could revolutionize the renewable energy landscape and help meet the world's energy needs. Yet, its potential remains largely untapped, as coating techniques compatible with R2R, such as slot die coating or blade coating, struggle to meet the high benchmark set by spin-coating methods. This difference roots in a multitude of hurdles, achieving dynamic drying like conventional spin coating, limited oven residence time, solvent toxicity, cost of material and uniform coating at scale. 

To address these challenges, a bottom-up approach is used to identify and reduce performance losses, bridging the gap between state-of-the-art PSCs and R2R deposition. Successful R2R coating of all active layers in a P–I–N PSC stack is demonstrated using a single-step perovskite ink.[1] Optimized drying conditions and multi-solvent blend systems are developed, resulting in a stabilized PCE of 12.2%. To improve this further, a modified architecture is introduced by depositing Poly(triaryl amine) (PTAA) via R2R and using Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as a buffer layer. This approach increases the power conversion efficiency to 15.2%.

Although fully R2R-coated devices were previously difficult to fabricate due to lack of a compatible back electrode, we present a fully R2R printed PSCs employing a compatible and low temperature processed carbon electrode. The n-i-p architecture, SnO₂/MAPbI₃/PEDOT/Carbon effectively addresses interlayer incompatibilities and recombination losses.[2] The results match the performance of evaporated gold electrodes, with small-scale device efficiencies of 13–14%. Our fully R2R-coated perovskite PSC achieved over 10% (10.8) stabilised PCE and demonstrating promising stability by maintaining 84% of its original efficiency over 1000 hours under specified conditions. This represents a significant leap forward in the scalable production of perovskite photovoltaics.

Despite considerable advancements, the performance of R2R fabricated PSCs has also been constrained due to the prevalent use of MAPbI₃ instead of more efficient alternatives. Although certain studies have reported impressive PCE of up to 17.4% using Cs_0.05FA_0.81MA_0.14Pb(I_0.83Br_0.17)[3], these achievements have relied on the use of toxic solvents, such as dimethyl formamide, which greatly limits their scalability. To address this challenge, we introduce an innovative two-step deposition process for efficient and stable FAPbI₃. Our approach involves the utilization of methanol and methylammonium acetate as solvents. This novel method represents a crucial development that marks a significant stride towards the scalable manufacturing of highly efficient PSCs.

Overall, this study aims to comprehensively address the limitations such as substrate roughness, incompatible interlayers, and environment friendly solvents for the continuous manufacturing of R2R slot die coated PSCs.