No abstract

can be produced via RF sputtering, [ 8a ] spray pyrolysis, [ 6a ] chemical vapor deposition [ 11 ] or electrodeposition techniques. [ 12 ] Here we investigate, for the fi rst time, Co 3 O 4 as an MO semiconductor light absorber for all-oxide PV cells. Thin fi lm heterojunction cells, [ 13 ] based on a compact TiO 2 layer produced by spray pyrolysis onto a fl uorine-doped tin oxide (FTO) substrate, followed by pulsed laser deposition of Co 3 O 4 , were investigated as a function of both their layer thicknesses and the Co 3 O 4 deposition temperature. To do this in an effi cient way, combinatorial device libraries [ 14 ] were produced with a thickness gradient ( Figure 1 d). An array of 169 round metal back-contacts, defi ning the cells, were deposited onto the library, allowing for PV performance characterization via automated high throughput methods. [ 15 ] We show that the pulsed laser deposition temperatures of the Co 3 O 4 absorber have a strong impact on device performance due to improved crystallinity and morphology. The library approach proved to be an effi cient method for determining the optimal layer thicknesses; the best performing cells (maximum power) were selected from each library created. Co 3 O 4 is investigated as a light absorber for all-oxide thin-fi lm photovoltaic cells because of its nearly ideal optical bandgap of around 1.5 eV. Thin fi lm TiO 2 /Co 3 O 4 heterojunctions are produced by spray pyrolysis of TiO 2 as a window layer, followed by pulsed laser deposition of Co 3 O 4 as a light absorbing layer. The photovoltaic performance is investigated as a function of the Co 3 O 4 deposition temperature and a direct correlation is found. The deposition temperature seems to affect both the crystallinity and the morphology of the absorber, which affects device performance. A maximum power of 22.7 µW cm −2 is obtained at the highest deposition temperature (600 °C)with an open circuit photovoltage of 430 mV and a short circuit photocurrent density of 0.2 mA cm −2 . Performing deposition at 600 °C instead of room temperature improves power by an order of magnitude and reduces the tail states (Urbach edge energy). These phenomena can be explained by larger grains that grows at high temperature, as opposed to many nucleation events that occur at lower temperature.

A TiO2|Co3O4|MoO3 all‐oxide solar cell produced by spray pyrolysis and pulsed laser deposition (PLD) onto a fluorine‐doped tin‐oxide (FTO) glass substrate with gold (Au) back contacts is demonstrated for the first time. A combinatorial approach is implemented to study the effect of molybdenum oxide (MoO3) as a recombination contact and the influence of the cobalt oxide (Co3O4) light‐absorber thickness on the performance of the solar cells. An increase of more than 200 mV in the open circuit voltage (Voc) is observed with a concurrent enhancement in terms of short‐circuit current (Jsc) and maximum power in comparison with TiO2|Co3O4 devices without the MoO3 layer. To understand the mechanism, full drift diffusion simulations are performed. The higher performance is attributed to elimination of a recombination process at the absorber/metal back‐contact interface and surface passivation by the MoO3 layer.

Advances in high-throughput materials fabrication and characterization techniques have resulted in faster rates of data collection and rapidly growing volumes of experimental data. To convert this mass of information into actionable knowledge of material process-structure-property relationships requires high-throughput data analysis techniques. This work explores the use of the Graph-based endmember extraction and labeling (GRENDEL) algorithm as a high-throughput method for analyzing structural data from combinatorial libraries, specifically, to determine phase diagrams and constituent phases from both x-ray diffraction and Raman spectral data. The GRENDEL algorithm utilizes a set of physical constraints to optimize results and provides a framework by which additional physics-based constraints can be easily incorporated. GRENDEL also permits the integration of database data as shown by the use of critically evaluated data from the Inorganic Crystal Structure Database in the x-ray diffraction data analysis. Also the Sunburst radial tree map is demonstrated as a tool to visualize material structure-property relationships found through graph based analysis.

The high open-circuit potential (Voc) achieved by perovskite solar cells (PSCs) is one of the keys to their success. The Voc analysis is essential to understand their working mechanisms. A large number of CH3NH3PbI3-xClx PSCs were fabricated on single large-area substrates and their Voc dependencies on illumination intensity, I0, were measured showing three distinctive regions. Similar results obtained in Al2O3 based PSCs relate the effect to the compact TiO2 rather than the mesoporous oxide. We propose that two working mechanisms control the Voc in PSCs. The rise of Voc at low I0 is determined by the employed semiconductor n-type contact (TiO2 or MgO coated TiO2). In contrast, at I0 close to AM1.5G, the employed oxide does not affect the achieved voltage. Thus, a change of regime from an oxide-dominated EFn (as in the dye sensitized solar cells) to an EFn, directly determined by the CH3NH3PbI3-xClx absorber is suggested.