Influence of the highest occupied molecular orbital energy level of the donor material on the effectiveness of the anode buffer layer in organic solar cells

Abstract

International audienceEfficiency of organic photovoltaic cells based on organic electron donor/organic electron acceptor junctions can be strongly improved when the transparent conductive Anode is coated with a Buffer Layer (ABL). Here, the effects of a metal (gold) or oxide (molybdenum oxide) ABL are reported, as a function of the Highest Occupied Molecular Orbital (HOMO) of different electron donors. The results indicate that a good matching between the work function of the anode and the highest occupied molecular orbital of the donor material is the major factor limiting the hole transfer efficiency. Indeed, gold is efficient as ABL only when the HOMO of the organic donor is close to its work function ΦAu. Therefore we show that the MoO3 oxide has a wider field of application as ABL than gold

Effect of CuI Anode Buffer Layer on the Growth of Polymers Thin Films and on the Performances of Organic Solar Cells

“…Since it is known that a MoO 3 anode buffer layer allows obtaining good band matching with electron donors, which HOMO value is around 5eV [42], it is clear from the present study that if this condition is necessary it is not sufficient in the case of the polymers studied in the present work. He is necessary furthermore to use an anode buffer layer which improves the morphology and therefore the conductivity of the polymer.…”

“…It can be concluded that the solar cell performances are far better when the ITO is recovered with CuI. As it can be seen in Table 2, MoO 3 , in the case of P4,2TA, improve the OPVC performance and since it is well known that MoO 3 allows achieving a good band matching between the ITO anode and the HOMO of the ED, whatever the HOMO value [42], we have tried to optimise the PCE of the OPVCs using a double ABL, 3 MoO CuI in our last samples. One can see that this double ABL allows improving significantly the PCE.…”

Theoretical evaluation of chemical substitutions along the main chain of poly(3‐hexylthienylene‐vinylene) for solar cell applications

“…Lower values for E HOMO usually bring an improvement in open‐circuit voltage of an OSC,, which makes the result obtained for P3HTV‐CN‐T of notable relevance. On the other hand, lower values for E HOMO tend to increase the hole collection barrier between the electron donor polymer and the anode, the latter being in general indium–tin oxide or fluorine‐doped tin oxide; this hole collection barrier is proportional to the energy difference between the work function of the anode and E HOMO of the electron donor polymer. However, this problem can be circumvented using another hole transporting material inserted between the electron donor polymer and the anode with a work function lower than that of the anode, but higher than that of the electron donor polymer; using a hole transporting material with an appropriate work function helps to decrease the global hole collection barrier by means of a cascade transport of holes.…”

“…On the other hand, lower values for E HOMO tend to increase the hole collection barrier between the electron donor polymer and the anode, the latter being in general indium–tin oxide or fluorine‐doped tin oxide; this hole collection barrier is proportional to the energy difference between the work function of the anode and E HOMO of the electron donor polymer. However, this problem can be circumvented using another hole transporting material inserted between the electron donor polymer and the anode with a work function lower than that of the anode, but higher than that of the electron donor polymer; using a hole transporting material with an appropriate work function helps to decrease the global hole collection barrier by means of a cascade transport of holes. The 12 derivatives that presented E HOMO lower than that of P3HTV were those in which the substituents have greater ability to withdraw electrons from the polymer chain, which agrees with the trend observed in the literature for these types of substituents , , , .…”

Electrical Excitation of Long-Range Surface Plasmons in PC/OLED Structure with Two Metal Nanolayers

“…The technical reason for choosing MoO 3 (Lumtec, Taiwan) as the material for the hole injection-transport layer (HTL) is that it does not dissolve in chlorobenzene that is used for the structure preparation, namely during the spin-coating deposition of the SY layer slightly above the transport layer. Besides this technical reason, MoO 3 has quite suitable alignment of energy levels for the band structure of the active layer and Au anode [ 30 ]. The energy level diagram of the OLED layers is presented in Fig.…”