Electro-optics of perovskite solar cells: supplementary information

Experimental detailsSupporting figuresMaterialsPreparation of methylammonium iodide (MAI)Device fabricationDual-source evaporationFigure S1: Optical absorption characterisation of CH3NH3PbI3 perovskite/polymer bilayer films. Figure S2 Typical CH3NH3PbI3 perovskite solar cells performance with different polymer p-type interlayers.Table S1 Solar cells performance statistics of perovskite solar cells (6 devices each) prepared using different polymer p-type interlayers. *Data for the devices prepared using DPP-DTT as the interlayer have limited statistics as most were shorted due to poor film uniformity. Figure S3 Scanning Electron Microscopy images of CH3NH3PbI3 perovskite film surfaces prepared under various thermal evaporation conditions (dual source evaporation temperatures).Figure S4 X-ray Diffraction (XRD) characteristics of perovskite films prepared at various PbI2 evaporation temperatures with fixed MAI temperature (100 °C). Figure S5 Flow chart showing the measurement technique used to obtain the perovskite optical constants (n, k). Figure S6 Static dielectric constant measured by Charge Extraction Under Linearly Increasing Voltage (CELIV). Figure S7 Optical constants (n, k) for all the non-junction materials used in this paper.Figure S8 Electro-optic modeling of the maximum short circuit current (Jsc) as a a function of the interlayers and perovskite junction thicknesses. Figure S9 Hysteresis of optimised CH3NH3PbI3 perovskite solar cells. Figure S10 Long term stability of CH3NH3PbI3 perovskite solar cells. Figure S11 Light intensity dependent short circuit current density of an optimised CH3NH3PbI3 perovskite solar cell

Room-temperature tilted-target sputtering deposition of highly transparent and low sheet resistance Al doped ZnO electrodes

Target-tilted room temperature sputtering of aluminium doped zinc oxide (AZO) provides transparent conducting electrodes with sheet resistances o

Loss mechanisms in fullerene-based low-donor content organic solar cells

Low-weight-percent donor content fullerene-based organic solar cells have been reported to have good efficiencies although the exact reason for their performance is still a matter of discussion. We use a solution processable hole-transporting poly(dendrimer) with minimal absorption in the visible region to study the blend-ratio dependency of energy-loss mechanisms in fullerene low-donor content organic solar cells in which [6,6]-phenyl-C-71-butyric acid methyl ester is used as the primary absorber. The photocurrent losses for each of the steps that govern the device performance have been assessed, with the optimized device performance achieved when the donor was at a concentration of 6 wt %. The 6 wt % donor device had balanced charge transport, and transient absorption spectra revealed that although the low-donor content devices suffered from a low-exciton-quenching rate, the dissociation efficiency of the resulting charge-transfer states was almost unity. That is, essentially all of the formed charge-transfer states led to charge-separated states. A gradual increase in the open-circuit voltage was observed as the donor ratio decreased from 50 to 6 wt %. Internal quantum-efficiency measurements indicated efficient formation of charge-separated states from the intermediate charge-transfer states and high charge-collection efficiency at low-donor content resulting in an overall higher external quantum efficiency despite the lower interfacial area. Overall, these measurements highlight the competing effects of exciton dissociation (favored by the high surface area associated with large donor content) and charge-transfer state dissociation, which we observe to be more efficient when the donor content is low

Indirect tip fabrication for scanning probe microscopy

Organohalide lead perovskite solar cells have emerged as a promising next-generation thin-film photovoltaic technology. It has been clearly recognized that interfacial engineering plays a critical role in cell performance. It has been also proposed that the open-circuit voltage is dependent on the ionization potential of the hole transport layer at the anode. In this communication, we report a simple modification of the anode with a triarylamine-based small molecule (<b>1</b>), which avoids the need to use standard hole transport materials and delivers a relatively high open-circuit voltage of 1.08 V and a power conversion efficiency of 16.5% in a simple planar architecture

Graphene-based transparent conducting electrodes for high efficiency flexible organic photovoltaics: elucidating the source of the power losses

Solution processed flexible organic solar cells (OSCs) are of interest due to their potential use as environmentally friendly, shapeable, or wearable energy. Such flexible devices require compatible transparent conducting electrodes (TCEs). The use of three-layer graphene as a useful TCE for flexible OSCs is reported. The conformal coating of the graphene-based TCE with good retention of performance was achieved using a bulk heterojunction (BHJ) active layer comprised of the non-polymeric molecular (5Z,5 ' Z)-5,5 '-[(5'",5'"'"'-{4,8-bis[5-(2-ethylhexyl)-4-n-hexylthiophen-2-yl]benzo[1,2-b:4,5-b ']dithiophene-2,6-diyl}bis{3 ',3 '',3'"-tri-n-hexyl-[2,2 ':5 ',2 '':5 '',2'"-quaterthiophene]-5'",5-diyl})bis(methanylylidene)]bis[3-n-hexyl-2-thioxothiazolidin-4-one] (BQR) donor and [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) as the acceptor. This material combination enables thick BHJ junctions to be used so that the roughness of the graphene surface did not lead to shorted devices. The best graphene/poly(ethylene terephthalate) (PET) devices (PET/graphene/molybdenum oxide/BHJ/calcium/aluminum) show a photoconversion efficiency (PCE) of 5.8%, which while excellent was lower than that of a similar device architecture that used ITO/glass as the anode. The power losses of the graphene/PET-based cells mainly resulted from absorption losses caused by the optical profile distribution in the device and the relatively high sheet resistance of the anode, leading to an 18% decrease in the short-circuit current and lower fill factor, respectively

An external quantum efficiency of &gt;20% from solution-processed poly(dendrimer) organic light-emitting diodes

Controlling the orientation of the emissive dipole has led to a renaissance of organic light-emitting diode (OLED) research, with external quantum efficiencies (EQEs) of >30% being reported for phosphorescent emitters. These highly efficient OLEDs are generally manufactured using evaporative methods and are comprised of small-molecule heteroleptic phosphorescent iridium(III) complexes blended with a host and additional layers to balance charge injection and transport. Large area OLEDs for lighting and display applications would benefit from low-cost solution processing, provided that high EQEs could be achieved. Here, we show that poly(dendrimer)s consisting of a non-conjugated polymer backbone with iridium(III) complexes forming the cores of first-generation dendrimer side chains can be co-deposited with a host by solution processing to give highly efficient devices. Simple bilayer devices comprising the emissive layer and an electron transport layer gave an EQE of >20% at luminances of up to ≈300 cd/m, showing that polymer engineering can enable alignment of the emissive dipole of solution-processed phosphorescent materials