Trap suppression in ordered organic photovoltaic heterojunctions

Abstract

High trap density in organic solar cells leads to the localized charge carrier and reduced carrier lifetime, limiting device efficiency. Here we summarize the recent advances of trap suppression by material design and device engineering.

Ternary polythiophene enables over 17% efficiency organic solar cells

“…The highest μ h and μ e of PT-CN:BTP-eC9 based devices contributed to the shortest charge carrier extraction time and inhibited charge carrier recombination in OSCs, since the charge carrier lifetime and mobility strongly depend on the trap density in the device. 37 The total trap densities of PTVT-T:BTP-eC9, PT-CN:BTP-eC9 and PT-2CN:BTP-eC9 based devices were further determined by using the SCLC method. 38 The total trap density in the device can be calculated according to the following formula: 39 where V TFL is the trap-filled-limit voltage, q is the elementary charge, N t is the total trap density, L is the thickness of the blend film, ε 0 is the permittivity of vacuum, and ε is the relative permittivity.…”

Regulating the miscibility of donors/acceptors to manipulate the morphology and reduce non-radiative recombination energy loss enables efficient organic solar cells

“…9,10 Thus, it is important to optimize the phase separation of the active layer in OSCs. In addition, the aggregation state, including crystallinity, 11,12 donor/acceptor interfaces, 13 density of states, 14,15 etc. of the active layer materials also has important impacts on the exciton dynamics and charge carrier recombination in the blend, which would be reflected in the energy loss ( E loss ) and thus open-circuit voltage ( V OC ) of OSCs, except for the difference between the highest occupied molecular orbital (HOMO) energy level of the donors and the lowest unoccupied molecular orbital (LUMO) energy level of the acceptors.…”