Benzodithiophene‐Based, Donor–Acceptor–π–Donor–Acceptor Systems as Hole Transporting Materials for Efficient Perovskite Solar Cells

Abstract

AbstractFour new donor–acceptor–π‐bridge–accepter–donor hole‐transporting materials (HTMs) were developed based on the 2,2′‐(4,8‐bis(octyloxy)benzo[1,2‐b:4,5‐b′]dithiophene (OBDT) core moiety functionalised with two diphenylamine‐based donor units as outlying moieties. The compounds were designed, synthesised and used in perovskite solar cells (PSCs). Each HTM was thoroughly characterized with various spectroscopic techniques, and the surface and cross‐sectional morphologies of the thin‐film topmost layer, steady‐state photoluminescence, hole mobility and PSC efficiency were estimated and correlated with a standard Spiro‐OMeTAD HTM. The stabilized photocurrent and power conversion efficiency (PCE) measurements at maximum power point tracking, and J‐Voc curves under forward, and reverse bias, were studied. The film of the methyl‐substituted derivative provided a very consistent and compact protected layer to the whole perovskite layer, which is the key to the enhancement of the Voc and fill factor (FF). The PSC device based on the methyl derivative as HTM showed a high PCE of 19.07 % (active area 0.42 cm2) which is compared to the SpiroOMeTAD control device (17.90 %; active area 0.42 cm2). Optimized devices retained about 90 % PCE for 60 days, suggesting the reported HTM framework as a promising material for PSC application, considering also that they are tuneable and can be synthesized on a large scale.