Solution processed semiconducting materials employed in photovoltaic technologies like organic solar cells and perovskite solar cells suffer from severe thermomechanical instability. In fact, our work in evaluating the fracture resistance of perovskite solar cells has revealed that the organic molecular materials, polymeric materials and perovskite absorber layers are all remarkably fragile. In these cells, the hole and electron selective contacts are the primary source of mechanical failure, fracturing cohesively or delaminating adhesively from the perovskite layer, which itself fails below ~1 J/m<sup>2</sup>. In addition, the inherent solubility of these organic materials limits their scope for application, preventing fabrication involving linear solvent deposition. To overcome this, a stiff, light-activated, node capable of generically transforming any solution processed organic material into a solvent- and fracture-resistant material has been developed. This node, TPBA has been used to TPBA to dramatically increase the fracture resistance of LiTFSi-doped PTAA 4-fold, overcoming it’s delamination from the perovskite layer and enabling the fabrication of n-i-p and p-i-n devices with increased efficiency. Our p-i-n device exemplifies the significant advantage of transforming PTAA into a solvent-resistant film, which prevents the formation of shunts during perovskite deposition.<br/>Turing our attention to the fragile perovskite, we developed polymeric scaffolds that shield the weak perovskite material from external stress, effectively partitioning the perovskite cell into hundreds of mechanically and chemically encapsulated cells. The mechanical integrity of this cell design is completed by covalently bonding our cross-linked hole-transporting composites to the scaffold resulting in perovskite solar cells that exhibit over a ten-fold increase in fracture resistance. In these mechanically robust cells, the PCE of the perovskite absorber is not diminished, matching the aerial PCE of monolithic perovskite solar cells. The synergy of cross-linked HTMs and our new scaffold architecture overcomes the mechanical fragility of perovskite solar cells, a potentially show-stopping challenge for this promising technology.<br/>

Overcoming the mechanical fragility of perovskite solar cells using novel cross-linking chemical additives and scaffolds

253rd National Meeting (2017)

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