PCDTBT based solar cells: one year of operation under real-world conditions

Abstract

We present measurements of the outdoor stability of PCDTBT:PC71BM based bulk heterojunction organic solar cells for over the course of a year. We find that the devices undergo a burn-in process lasting 450 hours followed by a TS80 lifetime of up to 6200 hours. We conclude that in the most stable devices, the observed TS80 lifetime is limited by thermally-induced stress between the device layers, as well as materials degradation as a result of edge-ingress of water or moisture through the encapsulation.

Encapsulation of Perovskite Solar Cells for High Humidity Conditions

“…Initial degradation was attributed to different possible factors, such as partial de‐doping of spiro‐OMeTAD, oxygen desorption from TiO 2 , changes at the contact, or changes in the perovskite absorber . Similar behavior (fast initial degradation followed by stable performance) was also observed in organic solar cells . Degradation processes in organic photovoltaics have been more comprehensively studied, including the processes responsible for the initial degradation, or the so‐called burn‐in loss.…”

“…Degradation processes in organic photovoltaics have been more comprehensively studied, including the processes responsible for the initial degradation, or the so‐called burn‐in loss. The burn‐in loss was attributed to the formation of sub‐bandgap states in the active layer owing to photo‐induced reactions . However, it was also proposed that multiple concurrent processes are responsible for the burn‐in loss, and that the origins of the burn‐in loss are material dependent .…”

Progress in Understanding Degradation Mechanisms and Improving Stability in Organic Photovoltaics

“…The only way to test the long‐term performance of a solar cell in true real‐world operating conditions is outdoor testing. Outdoor testing can be an effective way of identifying real‐world failure mechanisms, but because conditions are not controlled, it is difficult to assign degradation mechanisms to a specific stress or even combination of stressors. To resolve this issue and enable the mechanisms of degradation to be scientifically studied, researchers use a combination of artificial light, temperature control, encapsulation or atmospheric control, and power electronics to monitor the long‐term performance of solar cells in a controlled environment.…”

Degradation of inverted architecture CH3NH3PbI3‐xClx perovskite solar cells due to trapped moisture

“…Note however at this stage we cannot fully rule out additional reactions between the acidic PEDOT:PSS and ITO or perovskite resulting in additional degradation pathways . We note however that organic photovoltaics incorporating a PEDOT:PSS/ITO anode retain high efficiency after a period of at least one year . We also speculate that the locally reduced photocurrent observed in the LBIC images of aged devices (see Fig.…”

“…This conclusion is based on the fact that ingress of moisture through the encapsulation would most likely be evidenced through initial degradation toward the edge of the encapsulated film resulting from a diffusion‐limited process; a result that was not observed here. We suspect therefore that water that was initially bound in the PEDOT:PSS film (which is known to be highly hygroscopic ), underwent diffusion into the perovskite film and initiated its decomposition. However, it is also possible that the air‐based process used to deposit the perovskite resulted in a small fraction of water also being trapped within the perovskite layer itself.…”