Boosting the Power Conversion Efficiency of Perovskite Solar Cells Using Self-Organized Polymeric Hole Extraction Layers with High Work Function

Abstract

Methylammonium lead halide perovskites have been intensively studied [1-9]as promising photoabsorption and carrier transporter materials in solar cells because of their excellent semiconducting properties, [10,11]broad range of light absorption, and high extinction coeffi cient. [5,12]Hybrid solar cells with 10.9% power conversion effi ciency have been fabricated using a meso-superstructured organometal halide perovskite, which triggered a lot of attention in the solar cell research community; [5]the perovskite layer acts as both the light harvester and the hole conductor in the devices. [13] The bandgap of perovskites can be easily adjusted by incorporating metal cations,[14]inorganic anions, [15]or organic ligands. [10]Methylammonium lead halide perovskites also have the advantage of low-temperature (ca. 100 °C) solution processibility. Because of all these advantages, the power conversion effi ciencies (PCEs) of perovskite- based solar cells have reached 15.4% in a solar cell that incorporates a vacuum-deposited perovskite layer and a TiO 2 layer. [6]Although the PCE of perovskite solar cells has been increased remarkably, few reports [7,16,17]have considered solution- processed planar heterojunction (SP-PHJ) structure solar cells without using a mesoporous or compact semiconducting metal oxide (e.g., TiO 2) layer processed by high-temperature sintering, and the SP-PJH solar cells to date have shown lower PCE than those with a mesoporous or compact TiO 2 layer