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- W3162973271 abstract "In this work, the trap states in the conjugated polymer P3HT, often used as electron donor in organic bulk heterojunction solar cells, three commonly used fullerene based electron acceptors and P3HT:PC61BM blends were investigated. Furthermore, the trap states in the blend were compared with these of the pure materials. Concerning the lifetime of organic solar cells the influence of oxygen on P3HT and P3HT:PC61BM blends was studied. The experimental techniques used to investigate the trap states in the organic semiconductors were (fractional) thermally stimulated current (TSC) and current based deep level transient spectroscopy (Q-DLTS). Fractional TSC measurements on P3HT diodes revealed a quasi-continuous trap distribution. The distribution suggested two different traps in P3HT with approximately Gaussian energy distributions and maxima at about 50 meV and 105 meV. Thereby, the former was attributed to the tail states within the regular Gaussian density of states due to the low activation energy. The latter, deeper traps, however, exhibited a strong dependence on oxygen. Exposure of the P3HT diodes to oxygen, ambient air and synthetic (dry) air all revealed an increase of the deeper traps density with exposure time in the same manner. While the lower limit of the trap density in non aged P3HT samples was in the range of (1.0 − 1.2)×10^22 m^−3, it was more than doubled after an exposure of 50 h to air. An increase of the trap density with oxygen exposure time was also seen in the Q-DLTS measurements accompanied with an increase of the temperature dependence of the emission rates, indicating an enhanced formation of deeper traps. Due to the raise in density of the deeper traps, the charge carrier mobility in P3HT significantly decreased, as revealed by photo-CELIV measurements, resulting in a loss in mobility of about two orders of magnitude after 100 h exposure to synthetic air. The increased trap density was attributed to p-doping of P3HT by the transfer of an electron to adsorbed oxygen. This effect was partially reversible by applying vacuum to the sample for several hours or, more significantly, by a thermal treatment of the devices in nitrogen atmosphere. The trap states in the methanofullerenes PC61BM, bisPC61BM and PC71BM were investigated by TSC measurements. PC61BM yielded a broad quasi-continuous trap distribution with the maximum of the distribution at about 75 meV. The comparison of the TSC spectra of the three methanofullerenes exhibited significant differences in the trap states with higher activation energies of the most prominent traps in bisPC61BM and PC71BM compared to PC61BM. This probably originates from the different isomers bisPC61BM and PC71BM consist of. Each of the isomers yields different LUMO energies, where the lower ones can act as traps. The lower limit of the trap density of all of the three investigated fullerene derivatives exhibited values in the order of 10^22 m^−3, with the highest for bisPC61BM and the lowest for PC61BM. By applying fractional TSC measurements on P3HT:PC61BM solar cells, it was shown that the trap distribution in the blend is a superposition of the traps in pure P3HT and PC61BM and additional deeper traps in the range of about 250 meV to 400 meV. The origin of these additional traps, which can not be related to the pure materials, was attributed to a higher disorder in the blend and P3HT/PC61BM interfaces. This conclusion was supported by standard TSC and Q-DLTS measurements performed on pristine and annealed P3HT:PC61BM blends, exhibiting a higher ratio of the deep traps in the pristine samples. The lower limit of the trap density of the investigated annealed solar cells was in the range of (6−8)×10^22 m^−3, which was considerably higher than in the pure materials. The influence of oxygen on P3HT:PC61BM solar cells was investigated by exposure of the devices to synthetic air under specific conditions. Exposure of the solar cells to oxygen in the dark resulted in a strong decrease in the power conversion efficiency of 60 % within 120 h, which was only caused by a loss in short-circuit current. Simultaneous illumination of the solar cells during oxygen exposure strongly accelerated the degradation, resulting in an efficiency loss of 30 % within only 3 h. Thereby, short-circuit current, open-circuit voltage and fill factor all decreased in the same manner. TSC measurements revealed an increase of the density of deeper traps for both degradation conditions, which resulted in a decrease of the mobility, as investigated by CELIV measurements. However, these effects were less pronounced than in pure P3HT. Furthermore, an increase of the equilibrium charge carrier density with degradation time was observed, which was attributed to oxygen doping of P3HT. With the aid of macroscopic simulations, it was shown that the doping of the solar cells is the origin of the loss in short-circuit current for both degradation conditions." @default.
- W3162973271 created "2021-05-24" @default.
- W3162973271 creator A5027377135 @default.
- W3162973271 date "2011-01-01" @default.
- W3162973271 modified "2023-09-23" @default.
- W3162973271 title "Investigation of defect states in organic semiconductors: Towards long term stable materials for organic photovoltaics" @default.
- W3162973271 cites W1543187317 @default.
- W3162973271 cites W1626507888 @default.
- W3162973271 cites W1932694847 @default.
- W3162973271 cites W1963733469 @default.
- W3162973271 cites W1964560357 @default.
- W3162973271 cites W1965070998 @default.
- W3162973271 cites W1968772031 @default.
- W3162973271 cites W1969831726 @default.
- W3162973271 cites W1970112276 @default.
- W3162973271 cites W1970369837 @default.
- W3162973271 cites W1973862377 @default.
- W3162973271 cites W1976071035 @default.
- W3162973271 cites W1979470200 @default.
- W3162973271 cites W1980443870 @default.
- W3162973271 cites W1980954971 @default.
- W3162973271 cites W1981032730 @default.
- W3162973271 cites W1981296117 @default.
- W3162973271 cites W1987287543 @default.
- W3162973271 cites W1987628090 @default.
- W3162973271 cites W1988089526 @default.
- W3162973271 cites W1988244638 @default.
- W3162973271 cites W1990731378 @default.
- W3162973271 cites W1994981630 @default.
- W3162973271 cites W1996116239 @default.
- W3162973271 cites W2006292105 @default.
- W3162973271 cites W2008979257 @default.
- W3162973271 cites W2012299555 @default.
- W3162973271 cites W2013219470 @default.
- W3162973271 cites W2015426763 @default.
- W3162973271 cites W2017090236 @default.
- W3162973271 cites W2017322725 @default.
- W3162973271 cites W2019040430 @default.
- W3162973271 cites W2020388738 @default.
- W3162973271 cites W2022286385 @default.
- W3162973271 cites W2022810868 @default.
- W3162973271 cites W2025863277 @default.
- W3162973271 cites W2027306636 @default.
- W3162973271 cites W2028524168 @default.
- W3162973271 cites W2030320238 @default.
- W3162973271 cites W2031882613 @default.
- W3162973271 cites W2034588787 @default.
- W3162973271 cites W2035937342 @default.
- W3162973271 cites W2037641348 @default.
- W3162973271 cites W2037773093 @default.
- W3162973271 cites W2038877847 @default.
- W3162973271 cites W2041050929 @default.
- W3162973271 cites W2042598019 @default.
- W3162973271 cites W2043589381 @default.
- W3162973271 cites W2044300045 @default.
- W3162973271 cites W2048572512 @default.
- W3162973271 cites W2050033254 @default.
- W3162973271 cites W2052005018 @default.
- W3162973271 cites W2052590748 @default.
- W3162973271 cites W2052598320 @default.
- W3162973271 cites W2053356183 @default.
- W3162973271 cites W2054739227 @default.
- W3162973271 cites W2057594988 @default.
- W3162973271 cites W2057711086 @default.
- W3162973271 cites W2059867440 @default.
- W3162973271 cites W2061545219 @default.
- W3162973271 cites W2061675482 @default.
- W3162973271 cites W2071241757 @default.
- W3162973271 cites W2072321166 @default.
- W3162973271 cites W2073564344 @default.
- W3162973271 cites W2073895194 @default.
- W3162973271 cites W2076250463 @default.
- W3162973271 cites W2079794299 @default.
- W3162973271 cites W2079948913 @default.
- W3162973271 cites W2081469504 @default.
- W3162973271 cites W2081868215 @default.
- W3162973271 cites W2084868936 @default.
- W3162973271 cites W2086510379 @default.
- W3162973271 cites W2088032404 @default.
- W3162973271 cites W2088119498 @default.
- W3162973271 cites W2089394080 @default.
- W3162973271 cites W2089613089 @default.
- W3162973271 cites W2090422037 @default.
- W3162973271 cites W2092665187 @default.
- W3162973271 cites W2094505911 @default.
- W3162973271 cites W2101917173 @default.
- W3162973271 cites W2102124889 @default.
- W3162973271 cites W2112796640 @default.
- W3162973271 cites W2113798487 @default.
- W3162973271 cites W2126031985 @default.
- W3162973271 cites W2132658593 @default.
- W3162973271 cites W2136289801 @default.
- W3162973271 cites W2141517543 @default.
- W3162973271 cites W2142910748 @default.
- W3162973271 cites W2148176976 @default.
- W3162973271 cites W2153028269 @default.
- W3162973271 cites W2158767568 @default.
- W3162973271 cites W2164340598 @default.
- W3162973271 cites W3103956672 @default.
- W3162973271 cites W3106105323 @default.