Nanomaterials for solar cells applications

Bulk-heterojunction (BHJ) solar cells based on organic small molecules and polymers are the focus of increasing attention by science and commerce. In organic photovoltaic devices, a conjugated polymer layer is used as the donor, while a fullerene-based derivative is used as the acceptor. Poly(3,4-
ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is one of the most common interfacial materials used for organic BHJ solar cells. However, PEDOT:PSS is acidic and hygroscopic in nature, and it inherits microstructural inhomogeneities that cause not only gradual degradation, but a complete failure of BHJ solar cell devices. There is a growing interest in graphene-based solar cells because graphene-based materials offer ease of solution processability, high optical transparency, and high
power conversion efficiency. Graphene has been actively investigated for use as a transparent conducting electrode, and as a photoactive layer in fabricating solar cell devices. Power conversion efficiency in the range of 10% to 15% for graphene and inorganic semiconductor-based hybrid heterojunction solar cells, and 15.6% for graphene-containing perovskite solar cells has been observed. Organic materials-based solar cells degrade not only from environmental exposure, but also from
photo-oxidation caused by light illumination. In addition to higher power conversion efficiency, stability in graphene-based solar cells is critically important for commercial applications. In this review article, the stability of graphene-based heterojunction solar cells under atmospheric conditions is evaluated. Current studies show that the insertion of a graphene buffer layer into solar cell heterostructures stops
degradation and enhances stability in solar cell devices. Long-term environmental stability of graphenebased heterojunction solar cells for commercial applications is discussed.

We present the use of halide (PbCl 2 ) and non-halide lead precursors (Pb(OAc) 2 (OAc=CH 3 CH 2 COO -), Pb(NO 3 ) 2 , Pb(acac) 2 (acac=(CH 3 COCHCOCH 3 ) -) and PbCO 3 ) for the preparation of perovskite solar cells. We have confirmed by X-ray diffraction the growth of CH 3 NH 3 PbI 3 in all the analyzed cases, except for PbCO 3 , independently of the lead precursor used for the synthesis of the perovskite. In addition, different cell configurations, thin film and mesoporous scaffolds, TiO 2 or Al 2 O 3 , have also been prepared. We have observed that the lead precursor influences strongly on the structural properties of perovskite (grain size), as well as on the solar cell performance. Photovoltaic conversion efficiencies comparable to those achieved when using the commonly employed PbCl 2 have been obtained with Pb(OAc) 2 as lead source. Stability studies of the perovskite films and devices have also been carried out; demonstrating that the lead precursor also influences this aspect. Stability is strongly affected by atmosphere and illumination conditions, but also by the lead precursor employed for the perovskite synthesis. These results highlight that other lead sources, different to the commonly used PbCl 2 and PbI 2 , are also suitable for the development of PSCs, opening a new way for device performance optimization.

The rutile TiO2 of nanoparticles and microrods were simultaneously grown on FTO glass slide using a one-step hydrothermal process. CdS semiconducting nanocrystals were deposited on the surface of TiO2 surface using SILAR method. Moreover, the SEM micrograph studies, TiO2 nanorods were almost uniformly explored on FTO glass slide
pattern. The photovoltaic performances, as-prepared semiconductor sensitized solar cells (SSSCs) were studied and the maximum efficiency of FTO/TiO2/CdS-8/ZnS-2 sample was 0.78% were confirmed by sun solar simulator, overall the solar cell efficiency was determined with an increasing pattern of CdS deposition is reported in detail.