| Author: | Hossain, Mohammad Ismail |
| Title: | Optical analysis and experimental characterization of perovskite solar cells and color sensors |
| Advisors: | Tsang, Yuen Hong (AP) |
| Degree: | Ph.D. |
| Year: | 2020 |
| Subject: | Perovskite solar cells Solar cells Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Applied Physics |
| Pages: | xliii, 285 pages : color illustrations |
| Language: | English |
| Abstract: | Metal-halide perovskites are considered as one of the most exciting material systems due to their excellent optoelectronic properties. Notably, the multi-bandgap properties of perovskites have opened an emerging prospect for highly efficient tandem solar cell and color vision applications. So far, only perovskite-based tandem solar cells allow reaching energy conversion efficiencies exceeding 30% at low manufacturing cost. In this thesis, efficient solar cells and color sensors are studied based on metal-halide perovskite materials. Charge transport/contact layers have a significant impact on the electrical and optical properties of perovskite solar cells. Particularly, the front contact, which is a part of the junction of the solar cell, has to be efficient for realizing high energy conversion efficiency. The front contact must provide a lateral charge transport to the terminals and should allow efficient light incoupling while maintaining low optical losses. Hence, In the first part of the thesis, metal-oxides, such as titanium oxide (TiO2), nickel-oxide (NiO), zinc oxide (ZnO), etc., are investigated as potential front contacts for realizing efficient perovskite solar cells. High-quality metal oxide films are prepared by spray pyrolysis deposition (SPD), electron-beam physical vapor deposition (EBPVD), metal-organic chemical vapor deposition (MOCVD), and atomic layer deposition (ALD) techniques. As a first step, the study is carried out to investigate the planar perovskite solar cell performance with different front contacts, which is also used as a reference device structure for future investigations. Subsequently, the study is progressed to the textured perovskite solar cells, which combines the benefit of reaching high short-circuit current densities and energy conversion efficiencies due to efficient photon management. Efficient photon management allows enhancing photon absorptions in perovskite solar cells through light incoupling and/or light trapping. Herein, light incoupling and light trapping are investigated with the integration of surface textures (e.g. moth-eye, pyramid, optical metasurfaces, etc.) on top of planar perovskite solar cells. A non-resonant optical metasurface is additionally studied as an alternative light-trapping structure for realizing efficient perovskite solar cells, where an array of ZnO nanowires is realized by the templated electrodeposition through a mask of resist. The complex requirements of perovskite solar front contacts and the effect of the front contact on the optics of perovskite solar cells are described in this part of the study. The optics of solar cells is investigated by 3D finite-difference time-domain (FDTD) optical simulations and the electrical effects of solar cells are inspected by the 3D finite element method (FEM). Detailed discussions for the realization of metal oxide films and the influence of photon management on the photovoltaic performance are provided. The second part of this thesis deals with detailed balance calculations and photon management of perovskite-based tandem solar cells. An extended Shockley– Queisser model is used to identify fundamental loss mechanisms and link the losses to the optics of solar cells. The influence of free-carrier absorption of metal oxide films on the optics of low bandgap and/or tandem solar cells is investigated. Herein, an optimized design is proposed for the perovskite/silicon tandem solar cell, which has the potential to reach energy conversion efficiency beyond 30% with a short-circuit current density exceeding 20 mA cm-2 while using realistic device geometry. A hybrid approachis used to investigate the optics of perovskite/silicon tandem solar cells by combining 3D finite-difference time-domain simulations with experimental measurements. Furthermore, multi-bandgap perovskites are employed as absorbers for investigating high-efficiency perovskite/perovskite tandem solar cells at low cost. Details on the nanophotonic design of perovskite-based tandem solar cells are provided. In the final part of this thesis, multi-bandgap perovskite materials are considered for the realization of efficient vertically stacked colorsensors. The vertically stacked color sensor consists of three different energy bandgap perovskite diodes (channels), which allows exhibiting excellent color separation without having any color aliasing or color moiré error. The complex material properties of multi-bandgap perovskites are determined by the energy shift modeling. The quantum efficiency of the proposed vertically stacked color sensor is 3 times higher than the conventional filter-based color sensors. The current study focuses on the perovskite color sensor for achieving the quantum efficiency approaching 100%. The quantum efficiency of the investigated sensor is calculated by 3D finite-difference time-domain simulations. The study is further advanced to the realization of the multi-channel color sensor for detecting multispectral imaging, where six individual perovskite diodes are used for the sensor construction. The six-channel sensor outperforms all other characterized sensors. It enables the reconstruction of incident spectra that can be applied to a wide range of areas, such as health, communications, safety, and securities. The colorimetric characterization is performed based on the calculated spectral responsivities of the investigated color sensors. Details on the used materials, the device design, and the colorimetric analysis are provided. |
| Rights: | All rights reserved |
| Access: | open access |
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