Improving Film Formation and Photovoltage of Highly Efficient Inverted-Type Perovskite Solar Cells through the Incorporation of New Polymeric Hole Selective Layers

Abstract

Two chemically tailored new conjugated copolymers, HSL1 and HSL2, were developed and applied as hole selective layers to improve the anode interface of fullerene/perovskite planar heterojunction solar cells. The introduction of polar functional groups on the polymer side chains increases the surface energy of the hole selective layers (HSLs), which promote better wetting with the perovskite films and lead to better films with full coverage and high crystallinity. The deep highest occupied molecular orbital levels of the HSLs align well with the valence band of the perovskite semiconductors, resulted in increase photovoltage. The high lying lowest unoccupied molecule orbital level provides sufficient electron blocking ability to prevent electrons from reaching the anode and reduces the interfacial trap-assisted recombination at the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/perovskite interface, resulting in a longer charge-recombination lifetime and shorter charge-extraction time. In the presence of the HSLs, high-performance CH3NH3PbI x Cl3-x perovskite solar cells with a power conversion efficiency (PCE) of 16.6% (V oc: 1.07 V) and CH3NH3Pb(I0.3Br0.7) x Cl3-x cells with a PCE of 10.3% (V oc: 1.34 V) can be realized.