Toward a Scalable Fabrication of Perovskite Solar Cells under Fully Ambient Air Atmosphere: From Spin-Coating to Inkjet-Printing of Perovskite Absorbent Layer

Development of Greener and Stable Inkjet-Printable Perovskite Precursor Inks for All-Printed Annealing-Free Perovskite Solar Mini-Modules Manufacturing

Inkjet-printing is considered an emerging manufacturing process for developing perovskite solar cells (PSCs) with low material wastes and high production throughput. Up-to-now, all case studies on inkjet-printed PSCs are based on the exploitation of toxic solvents and/or high-molarity perovskite precursor inks that are known to enable the development of high-efficiency photovoltaics (PVs). The present study provides a new insight for developing lower-toxicity, high performance and stable (for more than 2 months) inkjet-printable perovskite precursor inks for fully ambient air processed PSCs. Using an ink composed of a green low vapor pressure noncoordinating solvent and only 0.8 m of perovskite precursors, the feasibility of fabricating high-quality and with minimum coffee-ring defects, annealing-free perovskite absorbent layers under ambient atmosphere is demonstrated. Noteworthily, the PSCs fabricated using the industry-compatible carbon-based hole transport material free architecture and the proposed ink present an efficiency >13% that is considered on the performance records for the under-consideration PV architecture employing an inkjet-printed active layer. Outstanding is also found the stability of the devices under the conditions determined by the ISOS-D-1 protocol (T95  = 1000 h). Finally, the perspective of upscaling PSCs to the mini-module level (100 cm2 aperture area) is demonstrated, with the upscaling losses to be as low as 8.3%rel dec-1 per upscaled active area.

Functional Materials for Fabrication of Carbon-Based Perovskite Solar Cells: Ink Formulation and Its Effect on Solar Cell Performance

Perovskite solar cells (PSCs) have rapidly developed into one of the most attractive photovoltaic technologies, exceeding power conversion efficiencies of 25% and as the most promising technology to complement silicon-based solar cells. Among different types of PSCs, carbon-based, hole-conductor-free PSCs (C-PSCs), in particular, are seen as a viable candidate for commercialization due to the high stability, ease of fabrication, and low cost. This review examines strategies to increase charge separation, extraction, and transport properties in C-PSCs to improve the power conversion efficiency. These strategies include the use of new or modified electron transport materials, hole transport layers, and carbon electrodes. Additionally, the working principles of various printing techniques for the fabrication of C-PSCs are presented, as well as the most remarkable results obtained from each technique for small-scale devices. Finally, the manufacture of perovskite solar modules using scalable deposition techniques is discussed.

A Bionic Interface to Suppress the Coffee-Ring Effect for Reliable and Flexible Perovskite Modules with a Near-90% Yield Rate

The inhomogeneity, poor interfacial contact, and pinholes caused by the coffee-ring effect severely affect the printing reliability of flexible perovskite solar cells (PSCs). Herein, inspired by the bio-glue of barnacles, a bionic interface layer (Bio-IL) of NiO_x /levodopa is introduced to suppress the coffee-ring effect during printing perovskite modules. The coordination effect of the sticky functional groups in Bio-IL can pin the three-phase contact line and restrain the transport of perovskite colloidal particles during the printing and evaporation process. Moreover, the sedimentation rate of perovskite precursor is accelerated due to the electrostatic attraction and rapid volatilization from an extraordinary wettability. The superhydrophilic Bio-IL affords an even spread over a large-area substrate, which boosts a complete and uniform liquid film for heterogeneous nucleation as well as crystallization. Perovskite films on different large-area substrates with negligible coffee-ring effect are printed. Consequently, inverted flexible PSCs and perovskite solar modules achieve a high efficiency of 21.08% and 16.87%, respectively. This strategy ensures a highly reliable reproducibility of printing PSCs with a near 90% yield rate.