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 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. The PSCs reported exhibit a power conversion efficiency (PCE) of 16.13% with excellent mechanical stability, retaining >90% of the PCE after 1000 bending cycles at a radius (R) of 6 mm. This PCE is amongst the highest reported values for flexible inverted PSCs fabricated on PEDOT:PSS. Although PSCs on rigid conducting glass substrates have been reported to exhibit >20% PCE, long-term stability is of great concern because of poor encapsulation. Solution processability of PSCs gives the freedom to develop them on flexible substrates, which is suitable for commercialization of PSCs. Herein, a novel encapsulation technology of sealing flexible PSCs inside cylindrical glass tubes (R = 8 mm) is being demonstrated. Encapsulated flexible devices retained 90% of the PCE after 6000 hours under ambient conditions.