Open AccessHigh-Performance Low-Bandgap Polymer Solar Cells With Optical Microcavity Employing Ultrathin Ag Film Electrode
Author(s) -
Ning Li,
Dazheng Chen,
Chunfu Zhang,
Jingjing Chang,
Zhenhua Lin,
Genquan Han,
Jincheng Zhang,
Lixin Guo,
Yue Hao
Publication year - 2016
Publication title -
ieee photonics journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.725
H-Index - 73
eISSN - 1943-0655
pISSN - 1943-0647
DOI - 10.1109/jphot.2016.2616579
Subject(s) - engineered materials, dielectrics and plasmas , photonics and electrooptics
In this paper, the performance of indium-tin-oxide (ITO) free microcavity polymer solar cells based on the thieno[3,4-b]thiophene/benzodithiophene:[6,6]-phenyl C71-butyric acid methyl ester (PTB7:PC71 BM) blend and transparent Ag electrode is systematically investigated by optical simulation. Here, the device has a structure of glass/opaque Ag/FPI-PEIE/PTB7:PC71BM/MoO3/ultrathin Ag/TeO 2, where the fulleropyrrolidine ethoxylated polyethylenimine (FPI-PEIE) and MoO3 act as charge transport layers and optical spacers, and the TeO2 serves as a transmittance enhancement layer. Compared to ITO-based devices, the microcavity device shows an obviously increased optical electric field intensity for the incident light wavelength from 600 to 750 nm, which agrees well with the better light absorption and lower reflectivity at relatively long wavelength. Further, enhanced performance is obtained from an optimizing top-illuminated device. It is noted that a remarkably enhanced short-circuit current density of 19.50 mA/cm2 is achieved for the microcavity device at optimized layer thicknesses, which is 11% higher than that of ITO-based devices. The improved performance of the microcavity device could be attributed to optically confined and reinforced incident light between two Ag reflective electrodes induced by the coherent interference, which boosts the light harvesting in the active layer, especially the long-wavelength incident photons. The results could provide a promising optical design for low-bandgap polymer solar cells.