Efficient bifacial semitransparent perovskite solar cells with silver thin film electrode

Bifacial semi-transparent perovskite solar cells (PSCs) are highly attractive for improving the efficiency of tandem solar cells and extending bifacial photovoltaic applications. However, the further improvement of bifacial performance has always been limited by the semitransparent electrode. Here we report an efficient triple-layer cathode of polyethyleneimine ethoxylate/silver/molybdenum oxide (PEIE/Ag/MoOx) for hysteresis-free planar PSCs with an inverted device configuration. Firstly, the optimal thickness of Ag electrode (11 nm) is achieved by theoretical calculation, and the fabricated PSC achieves the PCE of 8.04% at indium-tin-oxide (ITO) side and 5.24% at Ag film side. Then, by introducing the MoOx (10 nm) optical coupling layer and PEIE (10 nm) interfacial modifying layer, the resulted PSC shows an obviously increased PCEs of 13.55% (ITO side) and 8.41% (Ag side), which is 60% higher than that of Ag only PSCs. The optimized PSCs has a structure of Glass/ITO/Poly (3,4-ethylenedioxythiophene): poly(styrenesulfonate)/Methylammonium-Lead-Iodide (about 300 nm)/Phenyl-C61-butyric-acid-methyl-ester/PEIE/Ag/MoOx. It is thought that the enhanced Ag film transmittance by high-refractive-index MoOx and electron extraction ability by low-work-function PEIE contribute to the improved cathode property and bifacial PSC performance. Moreover, when a back-reflector is employed, the PCE of device could be further improved to 14.50% (ITO side) and 11.37% (Ag side).