Printable luminescent down shifter for enhancing efficiency and stability of organic photovoltaics

Abstract

The proof of concept of using luminescent down shifting (LDS) layers as alternative UV filters for P3HT:PCBM OPVs is demonstrated using a lanthanide-based metal complex. The results are verified using a combination of indoor light soaking, with single cell devices, and outdoor performance monitoring, using a 16-cell monolithically connected OPV module. By applying the LDS layer, a ~5% relative enhancement in photocurrent is observed for both sets of devices. More significantly, indoor light soaking tests on single cell devices without encapsulation showed an 850% enhancement in the measured half-life (T50%). The OPV modules were encapsulated and tested for outdoor stability over a 70 day period in the Negev desert, Israel . The modules made with the LDS filter are shown to match the stability of those made with a commercial UV filter and outperform the modules with no filter applied, with a 51% enhancement in the measured stability (T75%). Significantly, the work provides clear experimental evidence that the LDS layer can act as a UV filter in OPVs without compromising the efficiency of the solar cell, thus providing an added benefit over commercial UV filters.

Effect of Halide Composition on the Photochemical Stability of Perovskite Photovoltaic Materials

“…475 m) during clear-sky periods around 12:00 pm, where the solar spectrum was found to be very close to the standard AM 1.5 Gs olar spectrum. [38]). [35] The concentration of incident sunlight on the sample was measured using as pectrally blind pyranometer (thermopile) of 5% accuracy.D uring the exposure, the samples were thermally bonded to the top of at hermoelectric temperature controlled plate, which was set to 25 8C.…”

“…The sample and the pyranometer were mounted on af ixed angle stand (308 to horizontal, see for example Figure 6c in Ref. [38]). The samples experienced ambient temperatures (25-35 8C) measured by thermocouples.…”

Tuning the optical properties of luminescent down shifting layers based on organic dyes to increase the efficiency and lifetime of P3HT: PCBM photovoltaic devices

“…It can be clearly seen that the photocurrent generation decreased by using the KB layer, but increased with the KB:C153 mixture. Table 4 In the case of the KB:C153 mixture, the relative increase in JSC was about 20%, which is significantly greater than the previously reported for LDS layers applied to OPV's [19,26,32]. Such an improvement in the current density shows optimisation the optical properties of the luminescent material (or mixtures of these materials) is imperative to design efficient LDS layers.…”

“…The best PLQY values for LDS layers of the luminescent materials produced in this work are shown in Table 2, along with the parameters used for the production of the layer. The secondary purpose of the LDS layer is to improve the stability of the OPV device as it acts as a UV filter, limiting photo-degradation [19,26,32].…”

“…This approach employs a layer containing a luminescent material that absorbs photons at higher energies, where current generation is low, and re-emits at lower energy photons where the external quantum efficiency (EQE) of the OPV is at its highest. For OPVs, the proof of concept for LDS application has already been established by Kettle et al [19]. The LDS layer was shown to increase the lifetime of the OPV by reducing UV -induced degradation, and showed performance better than commercial UV filters owing to reduced reflection.…”