High performance perovskite solar cells using Cu9S5 supraparticles incorporated hole transport layers

We disclose novel photovoltaic device physics and present details of device mechanisms by investigating perovskite solar cells (PSCs) incorporating Cu9S5@SiO2 supraparticles (SUPs) into Spiro-OMeTAD based hole transport layers (HTLs). High quality colloidal Cu9S5 nanocrystals (NCs) were prepared using a hot-injection approach. Multiple Cu9S5 NCs were further embedded in silica to construct a Cu9S5@SiO2 SUP. Cu9S5@SiO2 SUPs were blended into Spiro-OMeTAD based HTLs with different weight ratios. Theoretical and experimental results show that the very strong light scattering or reflecting properties of Cu9S5@SiO2 SUPs blended in the PSC device in a proper proportion distribute to increase the light energy trapped within the device, leading to significant enhancement of light absorption in the active layer. Additionally, the incorporated Cu9S5@SiO2 SUPs can also promote the electrical conductivity and hole-transport capacity of the HTL. Significantly larger conductivity and higher hole injection efficiency were demonstrated in the HTM with the optimal weight ratios of Cu9S5@SiO2 SUPs. As a result, efficient Cu9S5 SUPs based PSC devices were obtained with average power conversion efficiency (PCE) of 18.21% at an optimal weight ratio of Cu9S5 SUPs. Compared with PSC solar cells without Cu9S5@SiO2 SUPs (of which the average PCE is 14.38%), a remarkable enhancement over 26% in average PCE was achieved. This study provides an innovative approach to efficiently promote the performance of PSC devices by employing optically stable, low-cost and green p-type semiconductor SUPs.