Infrared photodiodes based on organic semiconductors are promising for low-cost sensors that operate at room temperature. However, their realization remains hampered by poor device efficiency. Here, performance limitations are analyzed by evaluating the mobility-lifetime products and charge collection efficiency of devices operating in the shortwave infrared with a peak absorption at 1550 nm. Through complementary impedance and current-voltage measurements on devices with different donor-to-acceptor semiconductor ratios, a trade-off between mobility and recombination time and the need to balance between transport and interfacial charge transfer are observed. Thus, this study revisits the mobility-lifetime metric to shed new light on charge collection constraints in organic infrared photodiodes.
B.S. and T.N.N. were supported by the National Science Foundation (NSF) award ECCS\u20102222203. W.J.K. was supported by the NSF award ECCS\u20102318990. The work performed at The Georgia Institute of Technology was made possible through the Air Force Office of Scientific Research (AFOSR) under the support provided by the Organic Materials Chemistry Program (Grant FA9550\u201023\u20101\u20100654, Program Manager: Dr. Kenneth Caster) and the NSF award DMR\u20102323665. This work used the San Diego Nanotechnology Infrastructure of UCSD, which is supported by NSF ECCS\u20102025752.
