Recently, many kinds of printing processes have been studied to fabricate perovskite solar cells (PeSCs) for mass production. Among them, slot-die coating is a promising candidate for roll-to-roll processing because of high-throughput, easy module patterning, and a premetered coating system. In this work, we employed mixed lead precursors consisting of PbAc and PbCl to fabricate PeSCs via slot-die coating. We observed that slot-die-coated perovskite films based on the mixed lead precursors exhibited well-grown and uniform morphology, which was hard to achieve by using only a single lead source. Consequently, PeSCs made with this precursor system showed improved device performance and reproducibility over single PbAc. Lastly, a large-area module with an active area of 10 cm was fabricated with a power conversion efficiency of 8.3%.

Despite the potential of roll-to-roll processing for the fabrication of perovskite films, the realization of highly efficient and reproducible perovskite solar cells (PeSCs) through continuous coating techniques and low-temperature processing is still challenging. Here, we demonstrate that efficient and reliable CHNHPbI (MAPbI) films fabricated by a printing process can be achieved through synergetic effects of binary processing additives, N-cyclohexyl-2-pyrrolidone (CHP) and dimethyl sulfoxide (DMSO). Notably, these perovskite films are deposited from premixed perovskite solutions for facile one-step processing under a room-temperature and ambient atmosphere. The CHP molecules result in the uniform and homogeneous perovskite films even in the one-step slot-die system, which originate from the high boiling point and low vapor pressure of CHP. Meanwhile, the DMSO molecules facilitate the growth of perovskite grains by forming intermediate states with the perovskite precursor molecules. Consequently, fully printed PeSC based on the binary additive system exhibits a high PCE of 12.56% with a high reproducibility.

For the first time, the photovoltaic modules composed of small molecule were successfully fabricated by using roll-to-roll compatible printing techniques. In this study, blend films of small molecules, BTR and PCBM were slot-die coated using a halogen-free solvent system. As a result, high efficiencies of 7.46% and 6.56% were achieved from time-consuming solvent vapor annealing (SVA) treatment and roll-to-roll compatible solvent additive approaches, respectively. After successful verification of our roll-to-roll compatible method on small-area devices, we further fabricated large-area photovoltaic modules with a total active area of 10 cm, achieving a power conversion efficiency (PCE) of 4.83%. This demonstration of large-area photovoltaic modules through roll-to-roll compatible printing methods, even based on a halogen-free solvent, suggests the great potential for the industrial-scale production of organic solar cells (OSCs).

Despite significant progress in organic photovoltaics (OPVs), efforts to fabricate the small-molecule OPVs by scalable printing methods have hardly been devoted. Herein, we demonstrate large-area photovoltaic modules using two carbazole-based small molecules, named LGC-D023 and LGC-D073, with different alkyl terminal chain lengths. To investigate the influence of alkyl terminal chain length on slot-die coated devices, careful analysis of morphology and crystalline properties was also conducted as well as optimization of the slot-die coating process. Furthermore, under optimized conditions, large-area photovoltaic modules with an active area of 24 cm2 were fabricated by a slot-die coating method, exhibiting the champion power conversion efficiency (PCE) of 5.5% for LGC-D073 and 4.53% for LGC-D023, respectively. To the best our knowledge, this is the not only the largest area but also the highest efficiency for small-molecule OPV modules fabricated by roll-to-roll compatible printing techniques. As a result, our work proves that small molecules have great potential in terms of printed large-area photovoltaics and further applications for practical use in industry.