Single planar heterojunction organic solar cells based on CuPc-C60 small molecule active layer have been optimised using ITO anode electrode obtained by ion beam sputtering (IBS). The main interests in IBS process is an easy control of layer thickness and light transmission, and a better roughness of the anode compared to commercially available ITO, which can allow a PEDOT-PSS layer thickness optimisation.Comparison of two identical solar cells with commercially available ITO and our ITO obtained by IBS leads to a power conversion efficiency enhancement from 0.5% to 0.7%. Surprisingly, decreasing the serial resistance by increasing ITO thickness does not lead to further improvements, and this feature has been attributed to an increase of the ITO absorption and a possible cathode breaking due to a too thick cell structure. Better roughness of our ITO has permitted to decrease the PEDOT-PSS layer thickness, leading to an enhancement of the power conversion efficiency up to 1.3%. Optimising the cathode by adding an exciton blocking layer (BCP or LiF) has allowed us to decrease the active layer thickness, leading to a decrease of the cell serial resistance and giving rise to near 1.9% power conversion efficiency.

The harmful effect of toxic chemicals on natural ecosystems has led to an increasing demand for early-warning systems to detect those toxicants at very low concentrations levels. Whole-cell biosensors based either on chlorophyll fluorescence or enzyme (phosphatase and esterase) inhibition are constructed for real-time detection and on-line monitoring. Results show that these devices are sensitive to heavy metals and pesticides. The system allows the cells to operate in their natural environment which favours long term stability and reflects the toxic action mechanism providing therefore an ecological interest.

Chlorobenzene cast films of poly(3-hexylthiophene)-blend-[6,6]-phenyl C61 butyric acid methyl ester (P3HT-blend-PCBM) in 1:1 ratios were used in photovoltaic cells with the structure glass/ITO/PEDOT-blend-PSS/P3HT-blend-PCBM/LiF/Al. By varying the molecular weights of the P3HTs from 4500 to 280 000 g mol−1, it was found that P3HT molecular weight distributions had an important impact on cell characteristics and the most effective annealing temperature required.

Novel dyads containing [60]fullerene–perylenediimide units were developed as light-harvesting acceptors for the preparation of efficient solar cells. The antenna was grafted onto C60 with the aim to improve the absorption spectrum of materials used in bulk-heterojunction devices. Electrochemical and photophysical studies of these dyads in solution have revealed that there was no significant ground-state electronic interaction between the covalently bonded PDI and fullerene moieties. Steady-state fluorescence experiments evidenced an effective photoinduced energy transfer from the PDI moiety to C60. The potential use of these light-harvesting fullerenes in organic solar cells was estimated with their incorporation in bulk-heterojunctions using poly(3-hexylthiophene) as the conjugated $\pi $ -donor polymer.

In spite of the high potential of polymer photovoltaic (PV) cells, considerable improvement of their stability under operational conditions needs to be achieved. The few published data on the stability of such cells are devoted to accelerated indoor testing at elevated temperatures. The acceleration factor is undoubtedly dependent on the PV materials, the cell architecture and may vary with the degradation. We report preliminary results of long-term evaluation of PV performance of polymer cells under real sun operational conditions. The studied devices include three types of encapsulated polymer/fullerene cells which differed by the configuration and content of the photoactive layer: (1) bulk heterojunction of MEH-PPV:PCBM; (2) bulk heterojunction of P3HT:PCBM; (3) bilayer heterojunction P3CT-C60. The MEHPPV-PCBM cell exhibited the fastest degradation. The degradation of PV performance of the P3HT-PCBM cell was much slower while the P3CT-C60 device was found to be the most stable. Effect of restoration of I sc and V oc was found when the P3HT-PCBM and P3CT-C60 cells were kept in the dark overnight. The first I sc and V oc measurements every morning yielded the highest values compared to those during the rest of a day. While I sc recovered only partly and exhibited significant degradation during a month, V oc values recovered completely every night and showed almost no reduction on a long-term time scale.