Optical properties and limiting photocurrent of thin-film perovskite solar cells
Energy and Environmental Science Royal Society of Chemistry 8:2 (2014) 602-609
Abstract:
Metal-halide perovskite light-absorbers have risen to the forefront of photovoltaics research offering the potential to combine low-cost fabrication with high power-conversion efficiency. Much of the development has been driven by empirical optimisation strategies to fully exploit the favourable electronic properties of the absorber layer. To build on this progress, a full understanding of the device operation requires a thorough optical analysis of the device stack, providing a platform for maximising the power conversion efficiency through a precise determination of parasitic losses caused by coherence and absorption in the non-photoactive layers. Here we use an optical model based on the transfer-matrix formalism for analysis of perovskite-based planar heterojunction solar cells using experimentally determined complex refractive index data. We compare the modelled properties to experimentally determined data, and obtain good agreement, revealing that the internal quantum efficiency in the solar cells approaches 100%. The modelled and experimental dependence of the photocurrent on incidence angle exhibits only a weak variation, with very low reflectivity losses at all angles, highlighting the potential for useful power generation over a full daylight cycle.Recombination Kinetics in Organic-Inorganic Perovskites: Excitons, Free Charge, and Subgap States
Physical Review Applied American Physical Society (APS) 2:3 (2014) 034007
Polystyrene templated porous titania wells for quantum dot heterojunction solar cells.
ACS applied materials & interfaces 6:16 (2014) 14247-14252
Abstract:
Polystyrene spheres are used to template TiO2 with a single layer of 300 nm wells which are infilled with PbS quantum dots to form a heterojunction solar cell. The porous well device has an efficiency of 5.7% while the simple planar junction is limited to 3.2%. Using a combination of optical absorption and photocurrent transient decay measurement we determined that the performance enhancement comes from a combination of enhanced optical absorption and increased carrier lifetime.Electronic properties of meso-superstructured and planar organometal halide perovskite films: charge trapping, photodoping, and carrier mobility.
ACS nano 8:7 (2014) 7147-7155
Abstract:
Solution-processed organometal trihalide perovskite solar cells are attracting increasing interest, leading to high performances over 15% in thin film architectures. Here, we probe the presence of sub gap states in both solid and mesosuperstructured perovskite films and determine that they strongly influence the photoconductivity response and splitting of the quasi-Fermi levels in films and solar cells. We find that while the planar perovskite films are superior to the mesosuperstructured films in terms of charge carrier mobility (in excess of 20 cm(2) V(-1) s(-1)) and emissivity, the planar heterojunction solar cells are limited in photovoltage by the presence of sub gap states and low intrinsic doping densities.Anomalous hysteresis in perovskite solar cells
journal of physical chemistry letters American Chemical Society 5:9 (2014) 1511-1515