Diluted Organic Semiconductors in Photovoltaics

Abstract

Incorporation of insulating polymers or molecules into organic semiconductor films, creating so‐called diluted organic semiconductors, has been successfully used both in organic field‐effect transistors and organic light‐emitting diodes to reduce sensitivity to charge traps. However, application of this strategy in organic photovoltaics is challenging due to the complex requirements on the light‐absorbing blend layer. Herein, diluted donor–acceptor–insulator ternary organic solar cells are developed to improve mobility and decrease radiative and nonradiative recombination in the active layer. In addition, both thermal and environmental stability of the diluted ternary solar cells are enhanced. Finally, the diluted semiconductor approach enables large‐area solar cells to be fabricated where the loss in power density upon cell area upscaling is five times lower than for the equivalent binary cells.

Recent Progress of Organic Solar Cells with Insulating Polymers

“…Of late, Fahlman and coworkers introduced the trap‐diluted effect, which was achieved by incorporating insulating PVK in the photovoltaic system in this work, to suppress the trap state in OSCs. [ 50 ] The voltage loss caused by radiative and nonradiative recombination was reduced due to the less trap states in diluted organic semiconductors. Attractively, the resulting device showed improved mobility and performance, whereas the thermal and environmental stability were also enhanced.…”

Natural Product Betulin‐Based Insulating Polymer Filler in Organic Solar Cells

“…[ 11 ] To reproduce the trap‐dilution effect in OSCs, we previously used poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b’]dithiophene))‐alt‐(5,5‐(1’,3’‐di‐2‐thienyl‐5’,7’‐bis(2‐ethylhexyl) benzo [1’,2’‐c:4’,5’‐c’]dithiophene‐4,8‐dione)]: poly{[N,N'‐bis(2‐octyldodecyl) naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5'‐(2,2'‐bithiophene)} (PBDB‐T:N2200) with dominant donor ratio in an “ideal” OSC system. [ 31 ] The insulating filler PVK has suitable surface energy and molecular weight, which ensures the network penetration inside the BHJ, instead of aggregation at the bottom contact when blending is with high ratio (<60%). Multiple filler‐induced improvements have been achieved obtained including the reduction of radiative and non‐radiative recombination, enhancement of mobility, area scalability, and thermal and environmental stability.…”

“…[11] To reproduce the trap-dilution effect in OSCs, we previously used poly[ (2,6-(4,8- ) with dominant donor ratio in an "ideal" OSC system. [31] The insulating filler PVK has suitable surface energy and molecular weight, which ensures the network penetration inside the BHJ, instead of aggregation at the bottom contact when blending is with high ratio (<60%). Multiple fillerinduced improvements have been achieved obtained including the reduction of radiative and non-radiative recombination, enhancement of mobility, area scalability, and thermal and environmental stability.…”

Synergistic Effect of Poly(aryl ether ketone) Matrices via Rational Ternary Copolymerization Enables Efficient and Stable Organic Solar Cells

“…31 Fahlman et al proved that an interpenetrating D/A network can be maintained with improved PCEs by the BHJ films with insulating poly-(vinylcarbazole) concentrations even up to 60 wt %. 32 Table S1 summarizes the device efficiency for the reported organic photovoltaic systems with insulating polymers. It can be seen that the threshold concentration of the reported insulating polymer systems in BHJ layers is ranged from 2 to 60 wt % for optimizing device performance.…”

“…In our previous work, introduction of 5–30 wt % poly­(aryl ether)­s in PM6:Y6 blends can improve the efficiency, stability, and stretchability of OSCs. , Stingelin et al showed that the PCEs can be maintained at a high level for the polyethylene concentration even up to 50 wt % in BHJ layers . Fahlman et al proved that an interpenetrating D/A network can be maintained with improved PCEs by the BHJ films with insulating poly­(vinylcarbazole) concentrations even up to 60 wt % Table S1 summarizes the device efficiency for the reported organic photovoltaic systems with insulating polymers.…”