Highly efficient and stable semi-transparent perovskite solar modules with a trilayer anode electrode

Highly efficient and stable semi-transparent CH₃NH₃PbI₃ perovskite photovoltaic cells are realized by using an ITO/MoO_x bilayer conductive oxide as the anode electrode with a cyclopenta[2,1-b;3,4-b′]dithiophene (CT) based hole-transport material (HTM), which allows bifacial illumination from both sides of the electrodes. The wide bandgap MoO_x thin film is not only to be an electron blocking layer, but also to be a passivation layer which can withstand the excessive energy bombardment during the magnetron sputtering process for the deposition of a high-quality ITO thin film. Atomic-force microscopy images, transmittance spectra and water-droplet contact angle images show that the interfacial contact between MoO_x and hole transport layer (HTL) strongly influences the short-circuit current density (J_SC) and fill factor (FF). The highest power conversion efficiency (PCE) values for the bifacial perovskite solar cells (0.16 cm²) and modules (11.7 cm²) are 16.38% and 14.96%, respectively. In addition, the PCE of the ITO/MoO_x/CT-HTM based perovskite solar module decreases slowly toward a stable value (∼11%) for more than 700 h under wet environment conditions (70 ± 5 RH%).