Md. Anower Hossain

CdS/CdSe-sensitized nanostructured SnO(2) solar cells exhibiting record short-circuit photocurrent densities have been fabricated. Under simulated AM 1.5, 100 mW cm(-2) illumination, photocurrents of up to 17.40 mA cm(-2) are obtained, some 32% higher than that achieved by otherwise identical semiconductor-sensitized solar cells (SSCs) employing nanostructured TiO(2). An overall power conversion efficiency of 3.68% has been achieved for the SnO(2)-based SSCs, which compares very favorably to efficiencies obtained by the TiO(2)-based SSCs. The characteristics of these SSCs were studied in more detail by optical measurements, spectral incident photon-to-current efficiency (IPCE) measurements, and impedance spectroscopy (IS). The apparent conductivity of sensitized SnO(2) photoanodes is apparently too large to be measured by IS, yet for otherwise identical TiO(2) electrodes, clear electron transport features could be observed in impedance spectra, tacitly implying slower charge transport in TiO(2). Despite this, electron diffusion length measurements suggest that charge collection losses are negligible in both kinds of cell. SnO(2)-based SSCs exhibit higher IPCEs compared with TiO(2)-based SSCs which, considering the similar light harvesting efficiencies and the long electron diffusion lengths implied by IS, is likely to be due to a superior charge separation yield. The resistance to charge recombination is also larger in SnO(2)-based SSCs at any given photovoltage, and open-circuit photovoltages under simulated AM 1.5, 100 mW cm(-2) illumination are only 26-56 mV lower than those obtained for TiO(2)-based SSCs, despite the conduction band minimum of SnO(2) being hundreds of millielectronvolts lower than that of TiO(2).

Semiconductor-sensitized TiO2 solar cells employing CdSe as a light absorber demonstrate superior photovoltaic performance to the best-performing cascaded CdS/CdSe cells with practically identical optical density in the study. A careful comparison between CdSe and CdS/CdSe sensitized cells reveals that while CdS can greatly promote the subsequent growth of CdSe in the cascade electrodes and hence light harvesting, the presence of a CdS buffer layer impedes the injection of electrons from CdSe to TiO2 and accelerates charge recombination at the TiO2/sensitizer interface. As a result, better performance was achieved with CdSe-sensitized solar cells when light absorption is identical to that of CdS/CdSe cells, making the CdS buffer layer redundant. CdSe-sensitized TiO2 solar cells incorporating light scattering layers and an aqueous polysulfide electrolyte yielded an unprecedented power conversion efficiency of up to 5.21% under simulated AM 1.5, 100 mW cm−2 illumination.

Atomic layer deposition (ALD) can synthesise materials with atomic-scale precision. The ability to tune the material composition, film thickness with excellent conformality, allow low-temperature processing, and in-situ real-time monitoring makes this technique very appealing for a wide range of applications. In this review, we focus on the application of ALD layers in a wide range of solar cells. We focus on industrial silicon, thin film, organic and quantum dot solar cells. It is shown that the merits of ALD have already been exploited in a wide range of solar cells at the lab scale and that ALD is already applied in high-volume manufacturing of silicon solar cells.

Abstract The design and development of materials at the nanoscale has enabled efficient, cutting‐edge renewable energy storage, and conversion devices such as solar cells, water splitting, fuel cells, batteries, and supercapacitors. In addition to creating new materials, the ability to refine the structure and interface properties holds the key to achieving superior performance and durability of these devices. Atomic layer deposition (ALD) has become an important tool for nanofabrication as it allows the deposition of pin‐hole‐free films with atomic‐level thickness and composition control over high aspect ratio surfaces. ALD is successfully used to fabricate devices for renewable energy storage and conversion, for example, to deposit absorber materials, passivation layers, selective contacts, catalyst films, protection barriers, etc. In this review article, recent advances enabled by ALD in designing materials for high‐performance solar cells, catalytic energy conversion systems, batteries, and fuel cells, are summarized. The critical issues impeding the performance and durability of these devices are introduced and then the role of ALD in addressing them is discussed. Finally, the challenges in the implementation of ALD technique for nanofabrication on industrial scale are highlighted and a perspective on potential solutions is provided.