Gravure-printed ZnO in fully roll-to-roll printed inverted organic solar cells: Optimization of adhesion and performance

We present a gravure printing process for zinc oxide (ZnO) nanoparticle ink to be used as a hole-blocking layer in inverted organic solar cells, enabling the production of patterned devices with freedom of design. The printability of the ink is optimized in a pilot-scale roll-to-roll (R2R) process, leading to smooth layers having a thickness of few tens of nanometers. The properties of the printed ZnO film are further optimized using R2R post-printing plasma treatment, which leads to increased adhesion and power conversion efficiency (PCE). The functionality of the printed ZnO layer is demonstrated in fully R2R-printed inverted solar cells showing high performance (2.9?% mean PCE).