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The global Internet of Things (IoT) market is rapidly growing, with trillion new smart sensors being installed around the world by 2025. The most sensible choice for sustainable and energy-efficient IoT is to develop printable, light-weight, flexible, and low-cost IoT nodes, which do not contain toxic batteries, but instead are self-powered by the readily available ambient light, harvested by an indoor photovoltaic (IPV) technology. Among IPVs, perovskite-based devices have recently reached an outstanding indoor power conversion efficiency of 40.1%. Yet, beyond the attractive figures of merit, several open issues need still to be solved before commercialization. One main issue relates to the IPV materials and particularly the light absorber, i.e., perovskite. As traditional perovskites rely on toxic lead, harmful for the environment and leading to significant problem for IoT device recycling, there is a need to develop IPVs based on lead-free perovskite-inspired materials (PIMs) that can replicate the excellent optoelectronic properties of their toxic counterparts while being intrinsically stable (another major challenge for traditional Pb-perovskites). 

The exciting outcomes achieved in the previous PREIN 2022 project represent the starting point of the PINT research. The open questions to be addressed with the two classes of newly developed PIMs (CsMAFA-Sb and CABI) are the modest operational stability of IPVs and the poor sustainability of the PIMs processing. PINT project will contribute to these ambitious aims by targeting the following objectives (Os): 

O1: Develop a new family of lead-free  perovskite-inspired materials (PIMs), derived from CsMAFA-Sb and CABI, guided by Density Functional Theory (DFT) molecular modeling, with respect to the phase stability, bandgap, crystal structure, and defects.

O2: Establish an ad-hoc processing method (solvent, annealing conditions, etc.) for the new PIM compositions that optimizes the film morphology and controls the crystallization for maximized charge transport ability. 

O3: Achieve sustainable low-cost manufacturing of flexible PIM-based IPVs. Aalto team will develop flexible substrates based on biowaste-based lignocellulosics, hence with a lower footprint than typically used Indium Tin Oxide (ITO)/ Fluorine-doped Tin Oxide (FTO) substrates. 

O4: Investigate the stability of IPVs in operando conditions. 

In this project, we will for the first time: (i) explore chalcogenide-PIMs, (ii) look at PIM stability through advanced accelerated aging tests, and (iii) focus on the sustainability of the materials, solvents, and substrates constituting the IPVs. 

PROJECT PARTNERS: 

1. Hybrid Solar Cells (HSC), Tampere University (TAU); 
2. Solar Cell Technologies, VTT Technical Research Center; 
3. Multifunctional Materials Design, Aalto University; 
4. Molecular Modeling Research Group, The University of Eastern Finland (UEF).