Inclusion of Poly(N-isopropylacrylamide) Microgels into Inorganic-organic Hybrid Perovskite Solar Cells

Abstract

Solar cells have become increasingly substantial to our planet due to their providing us with green energy sources. Perovskite solar cells (PSCs) have been continuing to attract considerable attention owing to their excellent optical properties, band gap tunability, low cost, high efficiencies as well as their ability to be semitransparent, colourful, and flexible. Semitransparent perovskite solar cells (ST-PSCs) and colourful perovskite solar cells (C-PSCs) have become a point of interest to researchers around the world due to their versatile applications, including building integrated photovoltaics (BIPVs), such as roofs, facades and windows, and tandem solar cells. In this work, poly(N-isopropylacrylamide) microgel (PNP MGs) are introduced into the perovskite precursor solution in a one-step spin-coating deposition method for the first time. MGs are crosslinked polymer colloid particles that swell in a good solvent. The inclusion of PNP MGs into perovskites leads to the formation of highly ordered 2D non-close-packed particle arrays within the perovskite layer and control of the surface morphology. Additionally, the PNP MGs are used for the fabrication of ST-PSCs exhibiting great impact in improving both the power conversion efficiency (PCE) (11.64%) and average visible transmittance (AVT) (25.3%) for the MG-treated ST-PSCs compared to the control systems. In addition, The PNP MGs enhanced the light utilization efficiency (LUE) for the devices giving a value of 2.60% compared to 2.50% for the MG-free device. Finite difference time domain (FDTD) simulation data were used to support the experimental data, showing the effect of the MGs in improving the AVTs. The results suggest that the PNP MGs passivated the perovskite layer. Furthermore, in this work, colourful semitransparent perovskite solar cells (CST-PSCs) are fabricated by altering the contents of the PNP MGs. This approach results in the formation of structurally CST-PSCs that show colour in both reflected and transmitted geometries by scattering light. This occurs due to the non-hexagonal close-packed arrays within the MG-based perovskite films. The CST-PSCs exhibited a PCE of 10.60% and AVT of 25.52%. In this thesis, different compositions of perovskite are used, which are MAPb(I0.82Cl0.18)3, (MA0.39FA0.61Pb(I0.93Cl0.07)3, Cs0.05(FA0.98MA0.02)0.95Pb(I0.98Br0.02)3, and Cs0.12FA0.88Pb(I0.92Br0.08)3 (MA is methylammonium, and FA is formamidinium), which demonstrates the generality of this approach and good compatibility of the PNP MGs within perovskite. Thus, this PNP MG approach may provide a scalable potential technique for ST-PSCs and CST-PSCs applications as it offers a simple fabrication process that can be done using a one-step deposition method.