Solution-processed 3D/3D bilayer perovskite heterojunction solar cells

Abstract

Perovskite materials have garnered significant attention in both research and industry due to their excellent light absorption and unique optoelectronic properties. However, in perovskite solar cells (PSCs), severe non-radiative recombination at the interface between the carrier transport layer and the perovskite leads to performance losses, significantly hindering efficiency improvements. While the 2D/3D heterostructure can mitigate interfacial recombination losses, its asymmetric conductivity and potential uneven distribution may impair charge transfer and increase the series resistance of PSCs. To address the conflict between surface passivation and the conductivity of the passivated layer, we designed a novel heterojunction by substituting the 2D intermediate layer with a more conductive 3D perovskite. In this study, we introduce a bilayer FAPbI₃/MAPbI₃ perovskite prepared via solution processing. A 3D/3D double-layer perovskite structure was formed by depositing MAPbI₃ onto the FAPbI₃ substrate using a two-step dynamic spin-coating technique. UPS analysis confirmed this as a Type II 3D/3D perovskite heterojunction. By leveraging the energy band differences and transfer mechanisms between the two layers, the device achieves enhanced photoelectric conversion efficiency (PCE) and stability. The best-performing device reached a PCE of 22.95 %. Moreover, under continuous light-soaking operation at 25 °C in ambient air, it retained 83 % of its initial PCE after 600 h.