Application of ZnO electrode buffer layer in perovskite solar cells

ZnO has attracted extensive research in perovskite solar cells because of its high electron mobility, spectacular optical transparency, low-temperature processing, and ease of synthesis. Traditional electrode buffer layers used in perovskite solar cells have shown some drawbacks, such as high-temperature treatment, low transmittance, and complex fabrication procedures, which might not be fit for the further development of high-performance flexible perovskite solar cells. Here, we intend to give a systematic introduction to the fabrication and functions of ZnO electrode buffer layers (sol-gel method, pre-fabricated ZnO nanoparticle suspension, atomic layer deposition, spray pyrolysis, electrodeposition, chemical bath deposition, radio-frequency sputtering, metal organic chemical vapor deposition, and magnetron sputtering etc.). Particular attentions were paid to the understanding of the structure-property relations between the thickness, morphology, doping, and composition of ZnO electrode buffer layers and the performance of perovskite solar cells (open circuit voltage, current density, fill factor, power conversion efficiency, etc.). A perspective on the future development of ZnO electrode buffer layers and their applications in perovskite solar cells were also discussed in this review.