Efficient, Hysteresis Free, Inverted Planar Flexible Perovskite Solar Cells via Perovskite Engineering and Stability in Cylindrical Encapsulation
A p-i-n type flexible perovskite solar cell (PSC) employing PEDOT:PSS as a hole transport material was fabricated implementing a synergistic approach to tune the composition and morphology of the perovskite films. This was accomplished by the optimization of methylammonium-formamidinium double-cation perovskite, Pb(SCN)2 additive and different anti-solvents to make hysteresis-free flexible PSCs. PSCs being reported exhibit power conversion efficiency (PCE) of 16.13% with excellent mechanical stability, retaining > 90% of the PCE after 1000 bending cycles at the radius (R) of 6 mm. This PCE is amongst the highest reported values for the flexible inverted PSCs fabricated on PEDOT:PSS. Although PSCs on rigid conducting glass substrates have been reported to >20%, however, the long-term stability is of great concern because of poor encapsulation. Solution processibility of PSC gives the freedom to develop it on flexible substrate, which is suitable for commercialization of PSCs. Herein, a novel encapsulation technology of sealing the flexible PSCs inside the cylindrical glass tubes (R = 8 mm) is being demonstrated. Encapsulated flexible devices retained 90% of PCE after 6000 hours under ambient conditions.