One-step roll-to-roll air processed high efficiency perovskite solar cells

The rapid improvement in power conversion efficiencies (PCE) to record high levels have highlighted perovskite solar cells' great potential to be commercialized in the near future. Continuous roll-to-roll (R2R) processing on flexible substrates enables ultra low-cost and high throughput manufacturing, which is essential for perovskite solar cells to make a breakthrough in cost per Watt compared to commercially established solar cells technologies. Here we demonstrate a facile spin-coating-free and R2R compatible blowing-assisted drop-casting (BADC) method to prepare CH3NH3PbI3 films for perovskite solar cells. The crystallinity and morphology of CH3NH3PbI3 films and device performance are significantly improved by optimization of the formulation with an NH4Cl additive. The perovskite solar cell prepared in air with a maximum PCE of 19.48% is obtained using modified poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (m-PEDOT: PSS) as the hole transport layer (HTL). The cells based on the structure of ITO/m-PEDOT: PSS/CH3NH3PbI3/PCBM/Ca/Al exhibit negligible current hysteresis. The optimized formulation is then successfully applied to slot-die coating on glass and subsequently to R2R on a flexible substrate, giving record PCEs of 15.57% and 11.16%, respectively.