Implications of the device structure on the photo-stability of organic solar cells

Thin-film photovoltaic devices incorporating low-bandgap push-pull molecules dispersed in passive polymeric matrices

“…For matrix‐free devices containing F‐DTS and PC 71 BM, the highest value of PCE was only 0.49% when spin coating was carried out at 25 °C. In both series of matrix‐free devices, the low values of PCE can be attributed to films of poor quality, as observed in other cases in which small molecules are primary components of the active layers . Films deposited from solutions at 25 °C revealed a strong tendency for the components to crystallize, as demonstrated by higher roughness in images obtained by atomic force microscopy (AFM) and by the direct observation of birefringent crystals using optical microscopy under polarized light .…”

“…When crystals of PC 71 BM grow in the films, the surrounding regions are again depleted, but in this case material is now scavenged from non‐discoidal domains, leaving the disks intact in size and shape around growing crystals, as shown in Figure (d). However, the disks become more closely spaced as PC 71 BM is drawn toward growing crystals, both in films containing PEG150 and PS100 . Fully intact discoidal domains containing either ID(BTC) 2 or F‐DTS were found in close proximity to crystallites of PC 71 BM, as revealed by optical microscopy under polarized light and by fluorescence microscopy (Fig.…”

Vacuum deposited ternary mixture organic solar cells

“…SubPc is reasonably well studied in literature, providing high V oc values (owed to its deep HOMO) and high performance vacuum deposited small molecule OSCs [39][40][41][42]. ClInPc is somewhat less studied in literature, but it has also been highlighted for its high open circuit voltage OSCs, while granting near-IR absorption [43][44][45]. According to [46], the corresponding ternary OSCs are classified as 'parallellinkage' OSCs due to the strong inter-mixing of the active layer.…”

“…In the ternary OSC, the 25% donor content must be split between two different absorbing species, so the individual donor components cannot generate the same magnitude of photocurrent. Unfortunately, increasing the total donor content beyond 25% serves to reduce the V oc (due to Schottky band bending effects) [44], hinder charge transport [45,47], and reduce C 60 aggregate photocurrent [43], thus degrading OSC performance. These observations highlight one of the more critical aspects of the ternary OSC: one must carefully tune the mixed layer composition to balance photocurrent contributions from all three species.…”

“…Nevertheless, the overlapping As further validation of the hole transport limitations discussed above, we also studied the microsecond transient photocurrent response of ternary ClInPc:SubPc:C 60 OSCs. Transient photocurrent measurements have been used in a number of studies to examine charge transport phenomena in OSCs [53,57,58], and we recently used such measurements to obtain a more comprehensive understanding of the role of device architecture in OSC device performance [45,47]. These measurements thus serve as an ideal platform to understand the limitations of ClInPc:SubPc:C 60 OSCs in consideration of the previous discussions.…”