Neha Mahuli

Inorganic Hole Conducting Layers for Perovskite-Based Solar Cells

Hybrid organic-inorganic semiconducting perovskite photovoltaic cells are usually coupled with organic hole conductors. Here, we report planar, inverse CH3NH3PbI3-xClx-based cells with inorganic hole conductors. Using electrodeposited NiO as hole conductor, we have achieved a power conversion efficiency of 7.3%. The maximum VOC obtained was 935 mV with an average VOC value being 785 mV. Preliminary results for similar cells using electrodeposited CuSCN as hole conductor resulted in devices up to 3.8% in efficiency. The ability to obtain promising cells using NiO and CuSCN expands the presently rather limited range of available hole conductors for perovskite cells.

Atomic layer deposition of NiS and its application as cathode material in dye sensitized solar cell

Nickel sulfide (NiS) is grown by atomic layer deposition (ALD) using sequential exposures of bis(2,2,6,6-tetramethylheptane-3,5-dionate)nickel(II) [Ni(thd)2] and hydrogen sulfide (H2S) at 175 °C. Complementary combinations of in situ and ex situ characterization techniques are used to understand the deposition chemistry and the nature of film growth. The saturated growth rate of ca. 0.21 A per ALD cycle is obtained, which is constant within the ALD temperature window (175–250 °C). As deposited films on glass substrates are found polycrystalline without any preferred orientation. Electrical transport measurement reveals degenerative/semimetallic characteristics with a carrier concentration of ca. 9 × 1022 cm−3 at room temperature. The ALD grown NiS thin film demonstrates high catalytic activity for the reduction of I−/I3− electrolyte that opens its usage as cost-effective counter electrode in dye sensitized solar cells, replacing Pt.

Molecular layer deposition of alucone films using trimethylaluminum and hydroquinone

A hybrid organic–inorganic polymer film grown by molecular layer deposition (MLD) is demonstrated here. Sequential exposures of trimethylaluminum [Al(CH3)3] and hydroquinone [C6H4(OH)2] are used to deposit the polymeric films, which is a representative of a class of aluminum oxide polymers known as “alucones.” In-situ quartz crystal microbalance (QCM) studies are employed to determine the growth characteristics. An average growth rate of 4.1 A per cycle at 150 °C is obtained by QCM and subsequently verified with x-ray reflectivity measurements. Surface chemistry during each MLD-half cycle is studied in depth by in-situ Fourier transform infrared (FTIR) vibration spectroscopy. Self limiting nature of the reaction is confirmed from both QCM and FTIR measurements. The conformal nature of the deposit, typical for atomic layer deposition and MLD, is verified with transmission electron microscopy imaging. Secondary ion mass spectroscopy measurements confirm the uniform elemental distribution along the depth of ...

Atomic layer deposition of aluminum sulfide thin films using trimethylaluminum and hydrogen sulfide

Sequential exposures of trimethylaluminum and hydrogen sulfide are used to deposit aluminum sulfide thin films by atomic layer deposition (ALD) in the temperature ranging from 100 to 200 °C. Growth rate of 1.3 A per ALD cycle is achieved by in-situ quartz crystal microbalance measurements. It is found that the growth rate per ALD cycle is highly dependent on the purging time between the two precursors. Increased purge time results in higher growth rate. Surface limited chemistry during each ALD half cycle is studied by in-situ Fourier transformed infrared vibration spectroscopy. Time of flight secondary ion-mass spectroscopy measurement is used to confirm elemental composition of the deposited films.

Atomic layer deposition of titanium sulfide and its application in extremely thin absorber solar cells

Atomic layer deposition (ALD) of TiS2 is investigated with titanium tetrachloride and hydrogen sulfide precursors. In-situ quartz crystal microbalance and ex-situ x-ray reflectivity measurements are carried out to study self-limiting deposition chemistry and material growth characteristics. The saturated growth rate is found to be ca. 0.5 A/cycle within the ALD temperature window of 125–200 °C. As grown material is found poorly crystalline. ALD grown TiS2 is applied as a photon harvesting material for solid state sensitized solar cells with TiO2 as electron transport medium. Initial results with Spiro-OMeTAD as hole conducting layer show ca. 0.6% energy conversion efficiency under 1 sun illumination.

ALD grown absorber materials for bulk heterojunction solar cells

In this report we have discussed the need of conformal deposition of the low bandgap materials as absorber in solid-state bulk heterojunction devices. We demonstrated ALD grown Sb2S3 and TiSx thin films for photovoltaic applications. The deposition mechanism was studied in depth using in-situ quartz crystal microbalance (QCM). Need of modified reactor configuration for the uniform deposition of the material throughout the depth of the mesoporous host was discussed with elaborated comparative results for various absorber material device configurations.