am9b22058_si_001.pdf (576.4 kB)
Organic Thin-Film Red-Light Photodiodes with Tunable Spectral Response Via Selective Exciton Activation
journal contribution
posted on 2020-03-04, 22:29 authored by Shen Xing, Xiao Wang, Erjuan Guo, Hans Kleemann, Karl LeoRed
and near-infrared light detection is vital for numerous applications,
including full-color imaging, optical communication, and machine vision.
However, this development is hindered by a limited choice of small
band gap and narrow-bandwidth materials. Here, we report a device
principle with a simple organic planar heterojunction architecture
that enables a selective activation of excitons for tuning the photoresponse
spectra to fabricate thin-film, filterless, red-light organic photodiodes.
A sequential solution-processed active layer is formed by depositing
the top layer of PC71BM onto the predeposited bottom layer
of doped P3HT. By adjusting the ratio of PTB7 in P3HT, an improved
responsivity and a red-shift of the photoresponse peak from 645 to
745 nm are demonstrated simultaneously. Furthermore, the responsivity
of 745 nm is enhanced over 5 times with a narrow full width at half-maximum
of ∼50 nm at optimized doping ratio compared to the pristine
PTB7 device. As a result, a high specific detectivity in excess of
1012 Jones and broad linear dynamic range of 103 dB are
achieved. This design concept shows the possibility of realizing tunable
red-light selectivity even at relatively thin-film thickness, which
is intriguing for the implementation of high-resolution image sensors
in the near future.