Noncovalently functionalized conjugated polymers with conjugation-headed poly(ethylene glycol) as efficient hole-transport materials for nanocrystal photovoltaics

Abstract

Conjugated polymers (CPs) are demanding charge transport materials for various optoelectronic applications. To realize optimized characteristics of CPs for high-performance optoelectronic devices, their molecular ordering and interactions of CPs should be modulated by functionalizing conjugated backbones and side chains. However, typical covalent functionalization requires complicated and multiple syntheses and sometimes provides an unwanted deterioration of intrinsic charge transport properties of CPs. Here, we report a facile functionalization approach for CPs, which possibly affords enhanced charge carrier delivery with suppressed charge recombination, by incorporating a conjugation-headed surfactant (CHS). We found that the CHS effectively generates noncovalent functionalization on the conjugated backbone of CP through pi-pi interaction. Through comparisons using an surfactant without a conjugation-head, the CHS was revealed to be homogeneously and effectively mixed with CP, synergistically improving the morphological and crystal properties of CP films. Therefore, CPs functionalized with the CHS showed improved capabilities as hole-transport materials for nanocrystal photovoltaics; therefore, the corresponding devices recorded high efficiencies of >8% and > 13% in AgBiS2 and PbS nanocrystal photovoltaics, respectively.